/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.content;

import static android.Manifest.permission.INTERACT_ACROSS_USERS;
import static android.app.AppOpsManager.MODE_ALLOWED;
import static android.app.AppOpsManager.MODE_ERRORED;
import static android.app.AppOpsManager.MODE_IGNORED;
import static android.content.pm.PackageManager.PERMISSION_GRANTED;

import android.annotation.NonNull;
import android.annotation.Nullable;
import android.app.AppOpsManager;
import android.content.pm.PathPermission;
import android.content.pm.ProviderInfo;
import android.content.res.AssetFileDescriptor;
import android.content.res.Configuration;
import android.database.Cursor;
import android.database.MatrixCursor;
import android.database.SQLException;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Binder;
import android.os.Bundle;
import android.os.CancellationSignal;
import android.os.IBinder;
import android.os.ICancellationSignal;
import android.os.ParcelFileDescriptor;
import android.os.Process;
import android.os.RemoteException;
import android.os.UserHandle;
import android.os.storage.StorageManager;
import android.text.TextUtils;
import android.util.Log;

import java.io.File;
import java.io.FileDescriptor;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Objects;

Content providers are one of the primary building blocks of Android applications, providing content to applications. They encapsulate data and provide it to applications through the single ContentResolver interface. A content provider is only required if you need to share data between multiple applications. For example, the contacts data is used by multiple applications and must be stored in a content provider. If you don't need to share data amongst multiple applications you can use a database directly via SQLiteDatabase. 
When a request is made via a ContentResolver the system inspects the authority of the given URI and passes the request to the content provider registered with the authority. The content provider can interpret the rest of the URI however it wants. The UriMatcher class is helpful for parsing URIs.
The primary methods that need to be implemented are:

  
onCreate which is called to initialize the provider
  
query which returns data to the caller
  
insert which inserts new data into the content provider
  
update which updates existing data in the content provider
  
delete which deletes data from the content provider
  
getType which returns the MIME type of data in the content provider

Data access methods (such as insert and update) may be called from many threads at once, and must be thread-safe. Other methods (such as onCreate) are only called from the application main thread, and must avoid performing lengthy operations. See the method descriptions for their expected thread behavior.
Requests to ContentResolver are automatically forwarded to the appropriate ContentProvider instance, so subclasses don't have to worry about the details of cross-process calls.

Developer Guides
For more information about using content providers, read the
Content Providers
developer guide.

/**
 * Content providers are one of the primary building blocks of Android applications, providing
 * content to applications. They encapsulate data and provide it to applications through the single
 * {@link ContentResolver} interface. A content provider is only required if you need to share
 * data between multiple applications. For example, the contacts data is used by multiple
 * applications and must be stored in a content provider. If you don't need to share data amongst
 * multiple applications you can use a database directly via
 * {@link android.database.sqlite.SQLiteDatabase}.
 *
 * <p>When a request is made via
 * a {@link ContentResolver} the system inspects the authority of the given URI and passes the
 * request to the content provider registered with the authority. The content provider can interpret
 * the rest of the URI however it wants. The {@link UriMatcher} class is helpful for parsing
 * URIs.</p>
 *
 * <p>The primary methods that need to be implemented are:
 * <ul>
 *   <li>{@link #onCreate} which is called to initialize the provider</li>
 *   <li>{@link #query} which returns data to the caller</li>
 *   <li>{@link #insert} which inserts new data into the content provider</li>
 *   <li>{@link #update} which updates existing data in the content provider</li>
 *   <li>{@link #delete} which deletes data from the content provider</li>
 *   <li>{@link #getType} which returns the MIME type of data in the content provider</li>
 * </ul></p>
 *
 * <p class="caution">Data access methods (such as {@link #insert} and
 * {@link #update}) may be called from many threads at once, and must be thread-safe.
 * Other methods (such as {@link #onCreate}) are only called from the application
 * main thread, and must avoid performing lengthy operations.  See the method
 * descriptions for their expected thread behavior.</p>
 *
 * <p>Requests to {@link ContentResolver} are automatically forwarded to the appropriate
 * ContentProvider instance, so subclasses don't have to worry about the details of
 * cross-process calls.</p>
 *
 * <div class="special reference">
 * <h3>Developer Guides</h3>
 * <p>For more information about using content providers, read the
 * <a href="{@docRoot}guide/topics/providers/content-providers.html">Content Providers</a>
 * developer guide.</p>
 * </div>
 */
public abstract class ContentProvider implements ComponentCallbacks2 {

    private static final String TAG = "ContentProvider";

    /*
     * Note: if you add methods to ContentProvider, you must add similar methods to
     *       MockContentProvider.
     */

    private Context mContext = null;
    private int mMyUid;

    // Since most Providers have only one authority, we keep both a String and a String[] to improve
    // performance.
    private String mAuthority;
    private String[] mAuthorities;
    private String mReadPermission;
    private String mWritePermission;
    private PathPermission[] mPathPermissions;
    private boolean mExported;
    private boolean mNoPerms;
    private boolean mSingleUser;

    private final ThreadLocal<String> mCallingPackage = new ThreadLocal<>();

    private Transport mTransport = new Transport();

    
Construct a ContentProvider instance.  Content providers must be
declared
in the manifest, accessed with ContentResolver, and created automatically by the system, so applications usually do not create ContentProvider instances directly. 
At construction time, the object is uninitialized, and most fields and methods are unavailable. Subclasses should initialize themselves in onCreate, not the constructor. 
Content providers are created on the application main thread at
application launch time.  The constructor must not perform lengthy
operations, or application startup will be delayed.
/**
     * Construct a ContentProvider instance.  Content providers must be
     * <a href="{@docRoot}guide/topics/manifest/provider-element.html">declared
     * in the manifest</a>, accessed with {@link ContentResolver}, and created
     * automatically by the system, so applications usually do not create
     * ContentProvider instances directly.
     *
     * <p>At construction time, the object is uninitialized, and most fields and
     * methods are unavailable.  Subclasses should initialize themselves in
     * {@link #onCreate}, not the constructor.
     *
     * <p>Content providers are created on the application main thread at
     * application launch time.  The constructor must not perform lengthy
     * operations, or application startup will be delayed.
     */
    public ContentProvider() {
    }

    
Constructor just for mocking.
Params:
context – A Context object which should be some mock instance (like the instance of MockContext).
readPermission – The read permision you want this instance should have in the test, which is available via getReadPermission().
writePermission – The write permission you want this instance should have in the test, which is available via getWritePermission().
pathPermissions – The PathPermissions you want this instance should have in the test, which is available via getPathPermissions().
@hide
/**
     * Constructor just for mocking.
     *
     * @param context A Context object which should be some mock instance (like the
     * instance of {@link android.test.mock.MockContext}).
     * @param readPermission The read permision you want this instance should have in the
     * test, which is available via {@link #getReadPermission()}.
     * @param writePermission The write permission you want this instance should have
     * in the test, which is available via {@link #getWritePermission()}.
     * @param pathPermissions The PathPermissions you want this instance should have
     * in the test, which is available via {@link #getPathPermissions()}.
     * @hide
     */
    public ContentProvider(
            Context context,
            String readPermission,
            String writePermission,
            PathPermission[] pathPermissions) {
        mContext = context;
        mReadPermission = readPermission;
        mWritePermission = writePermission;
        mPathPermissions = pathPermissions;
    }

    
Given an IContentProvider, try to coerce it back to the real
ContentProvider object if it is running in the local process.  This can
be used if you know you are running in the same process as a provider,
and want to get direct access to its implementation details.  Most
clients should not nor have a reason to use it.
Params:
abstractInterface – The ContentProvider interface that is to be
             coerced.
Returns:
If the IContentProvider is non-null and local, returns its actual ContentProvider instance. Otherwise returns null.
@hide
/**
     * Given an IContentProvider, try to coerce it back to the real
     * ContentProvider object if it is running in the local process.  This can
     * be used if you know you are running in the same process as a provider,
     * and want to get direct access to its implementation details.  Most
     * clients should not nor have a reason to use it.
     *
     * @param abstractInterface The ContentProvider interface that is to be
     *              coerced.
     * @return If the IContentProvider is non-{@code null} and local, returns its actual
     * ContentProvider instance.  Otherwise returns {@code null}.
     * @hide
     */
    public static ContentProvider coerceToLocalContentProvider(
            IContentProvider abstractInterface) {
        if (abstractInterface instanceof Transport) {
            return ((Transport)abstractInterface).getContentProvider();
        }
        return null;
    }

    
Binder object that deals with remoting.
@hide
/**
     * Binder object that deals with remoting.
     *
     * @hide
     */
    class Transport extends ContentProviderNative {
        AppOpsManager mAppOpsManager = null;
        int mReadOp = AppOpsManager.OP_NONE;
        int mWriteOp = AppOpsManager.OP_NONE;

        ContentProvider getContentProvider() {
            return ContentProvider.this;
        }

        @Override
        public String getProviderName() {
            return getContentProvider().getClass().getName();
        }

        @Override
        public Cursor query(String callingPkg, Uri uri, @Nullable String[] projection,
                @Nullable Bundle queryArgs, @Nullable ICancellationSignal cancellationSignal) {
            uri = validateIncomingUri(uri);
            uri = maybeGetUriWithoutUserId(uri);
            if (enforceReadPermission(callingPkg, uri, null) != AppOpsManager.MODE_ALLOWED) {
                // The caller has no access to the data, so return an empty cursor with
                // the columns in the requested order. The caller may ask for an invalid
                // column and we would not catch that but this is not a problem in practice.
                // We do not call ContentProvider#query with a modified where clause since
                // the implementation is not guaranteed to be backed by a SQL database, hence
                // it may not handle properly the tautology where clause we would have created.
                if (projection != null) {
                    return new MatrixCursor(projection, 0);
                }

                // Null projection means all columns but we have no idea which they are.
                // However, the caller may be expecting to access them my index. Hence,
                // we have to execute the query as if allowed to get a cursor with the
                // columns. We then use the column names to return an empty cursor.
                Cursor cursor = ContentProvider.this.query(
                        uri, projection, queryArgs,
                        CancellationSignal.fromTransport(cancellationSignal));
                if (cursor == null) {
                    return null;
                }

                // Return an empty cursor for all columns.
                return new MatrixCursor(cursor.getColumnNames(), 0);
            }
            final String original = setCallingPackage(callingPkg);
            try {
                return ContentProvider.this.query(
                        uri, projection, queryArgs,
                        CancellationSignal.fromTransport(cancellationSignal));
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public String getType(Uri uri) {
            uri = validateIncomingUri(uri);
            uri = maybeGetUriWithoutUserId(uri);
            return ContentProvider.this.getType(uri);
        }

        @Override
        public Uri insert(String callingPkg, Uri uri, ContentValues initialValues) {
            uri = validateIncomingUri(uri);
            int userId = getUserIdFromUri(uri);
            uri = maybeGetUriWithoutUserId(uri);
            if (enforceWritePermission(callingPkg, uri, null) != AppOpsManager.MODE_ALLOWED) {
                return rejectInsert(uri, initialValues);
            }
            final String original = setCallingPackage(callingPkg);
            try {
                return maybeAddUserId(ContentProvider.this.insert(uri, initialValues), userId);
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public int bulkInsert(String callingPkg, Uri uri, ContentValues[] initialValues) {
            uri = validateIncomingUri(uri);
            uri = maybeGetUriWithoutUserId(uri);
            if (enforceWritePermission(callingPkg, uri, null) != AppOpsManager.MODE_ALLOWED) {
                return 0;
            }
            final String original = setCallingPackage(callingPkg);
            try {
                return ContentProvider.this.bulkInsert(uri, initialValues);
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public ContentProviderResult[] applyBatch(String callingPkg,
                ArrayList<ContentProviderOperation> operations)
                throws OperationApplicationException {
            int numOperations = operations.size();
            final int[] userIds = new int[numOperations];
            for (int i = 0; i < numOperations; i++) {
                ContentProviderOperation operation = operations.get(i);
                Uri uri = operation.getUri();
                userIds[i] = getUserIdFromUri(uri);
                uri = validateIncomingUri(uri);
                uri = maybeGetUriWithoutUserId(uri);
                // Rebuild operation if we changed the Uri above
                if (!Objects.equals(operation.getUri(), uri)) {
                    operation = new ContentProviderOperation(operation, uri);
                    operations.set(i, operation);
                }
                if (operation.isReadOperation()) {
                    if (enforceReadPermission(callingPkg, uri, null)
                            != AppOpsManager.MODE_ALLOWED) {
                        throw new OperationApplicationException("App op not allowed", 0);
                    }
                }
                if (operation.isWriteOperation()) {
                    if (enforceWritePermission(callingPkg, uri, null)
                            != AppOpsManager.MODE_ALLOWED) {
                        throw new OperationApplicationException("App op not allowed", 0);
                    }
                }
            }
            final String original = setCallingPackage(callingPkg);
            try {
                ContentProviderResult[] results = ContentProvider.this.applyBatch(operations);
                if (results != null) {
                    for (int i = 0; i < results.length ; i++) {
                        if (userIds[i] != UserHandle.USER_CURRENT) {
                            // Adding the userId to the uri.
                            results[i] = new ContentProviderResult(results[i], userIds[i]);
                        }
                    }
                }
                return results;
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public int delete(String callingPkg, Uri uri, String selection, String[] selectionArgs) {
            uri = validateIncomingUri(uri);
            uri = maybeGetUriWithoutUserId(uri);
            if (enforceWritePermission(callingPkg, uri, null) != AppOpsManager.MODE_ALLOWED) {
                return 0;
            }
            final String original = setCallingPackage(callingPkg);
            try {
                return ContentProvider.this.delete(uri, selection, selectionArgs);
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public int update(String callingPkg, Uri uri, ContentValues values, String selection,
                String[] selectionArgs) {
            uri = validateIncomingUri(uri);
            uri = maybeGetUriWithoutUserId(uri);
            if (enforceWritePermission(callingPkg, uri, null) != AppOpsManager.MODE_ALLOWED) {
                return 0;
            }
            final String original = setCallingPackage(callingPkg);
            try {
                return ContentProvider.this.update(uri, values, selection, selectionArgs);
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public ParcelFileDescriptor openFile(
                String callingPkg, Uri uri, String mode, ICancellationSignal cancellationSignal,
                IBinder callerToken) throws FileNotFoundException {
            uri = validateIncomingUri(uri);
            uri = maybeGetUriWithoutUserId(uri);
            enforceFilePermission(callingPkg, uri, mode, callerToken);
            final String original = setCallingPackage(callingPkg);
            try {
                return ContentProvider.this.openFile(
                        uri, mode, CancellationSignal.fromTransport(cancellationSignal));
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public AssetFileDescriptor openAssetFile(
                String callingPkg, Uri uri, String mode, ICancellationSignal cancellationSignal)
                throws FileNotFoundException {
            uri = validateIncomingUri(uri);
            uri = maybeGetUriWithoutUserId(uri);
            enforceFilePermission(callingPkg, uri, mode, null);
            final String original = setCallingPackage(callingPkg);
            try {
                return ContentProvider.this.openAssetFile(
                        uri, mode, CancellationSignal.fromTransport(cancellationSignal));
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public Bundle call(
                String callingPkg, String method, @Nullable String arg, @Nullable Bundle extras) {
            Bundle.setDefusable(extras, true);
            final String original = setCallingPackage(callingPkg);
            try {
                return ContentProvider.this.call(method, arg, extras);
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public String[] getStreamTypes(Uri uri, String mimeTypeFilter) {
            uri = validateIncomingUri(uri);
            uri = maybeGetUriWithoutUserId(uri);
            return ContentProvider.this.getStreamTypes(uri, mimeTypeFilter);
        }

        @Override
        public AssetFileDescriptor openTypedAssetFile(String callingPkg, Uri uri, String mimeType,
                Bundle opts, ICancellationSignal cancellationSignal) throws FileNotFoundException {
            Bundle.setDefusable(opts, true);
            uri = validateIncomingUri(uri);
            uri = maybeGetUriWithoutUserId(uri);
            enforceFilePermission(callingPkg, uri, "r", null);
            final String original = setCallingPackage(callingPkg);
            try {
                return ContentProvider.this.openTypedAssetFile(
                        uri, mimeType, opts, CancellationSignal.fromTransport(cancellationSignal));
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public ICancellationSignal createCancellationSignal() {
            return CancellationSignal.createTransport();
        }

        @Override
        public Uri canonicalize(String callingPkg, Uri uri) {
            uri = validateIncomingUri(uri);
            int userId = getUserIdFromUri(uri);
            uri = getUriWithoutUserId(uri);
            if (enforceReadPermission(callingPkg, uri, null) != AppOpsManager.MODE_ALLOWED) {
                return null;
            }
            final String original = setCallingPackage(callingPkg);
            try {
                return maybeAddUserId(ContentProvider.this.canonicalize(uri), userId);
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public Uri uncanonicalize(String callingPkg, Uri uri) {
            uri = validateIncomingUri(uri);
            int userId = getUserIdFromUri(uri);
            uri = getUriWithoutUserId(uri);
            if (enforceReadPermission(callingPkg, uri, null) != AppOpsManager.MODE_ALLOWED) {
                return null;
            }
            final String original = setCallingPackage(callingPkg);
            try {
                return maybeAddUserId(ContentProvider.this.uncanonicalize(uri), userId);
            } finally {
                setCallingPackage(original);
            }
        }

        @Override
        public boolean refresh(String callingPkg, Uri uri, Bundle args,
                ICancellationSignal cancellationSignal) throws RemoteException {
            uri = validateIncomingUri(uri);
            uri = getUriWithoutUserId(uri);
            if (enforceReadPermission(callingPkg, uri, null) != AppOpsManager.MODE_ALLOWED) {
                return false;
            }
            final String original = setCallingPackage(callingPkg);
            try {
                return ContentProvider.this.refresh(uri, args,
                        CancellationSignal.fromTransport(cancellationSignal));
            } finally {
                setCallingPackage(original);
            }
        }

        private void enforceFilePermission(String callingPkg, Uri uri, String mode,
                IBinder callerToken) throws FileNotFoundException, SecurityException {
            if (mode != null && mode.indexOf('w') != -1) {
                if (enforceWritePermission(callingPkg, uri, callerToken)
                        != AppOpsManager.MODE_ALLOWED) {
                    throw new FileNotFoundException("App op not allowed");
                }
            } else {
                if (enforceReadPermission(callingPkg, uri, callerToken)
                        != AppOpsManager.MODE_ALLOWED) {
                    throw new FileNotFoundException("App op not allowed");
                }
            }
        }

        private int enforceReadPermission(String callingPkg, Uri uri, IBinder callerToken)
                throws SecurityException {
            final int mode = enforceReadPermissionInner(uri, callingPkg, callerToken);
            if (mode != MODE_ALLOWED) {
                return mode;
            }

            if (mReadOp != AppOpsManager.OP_NONE) {
                return mAppOpsManager.noteProxyOp(mReadOp, callingPkg);
            }

            return AppOpsManager.MODE_ALLOWED;
        }

        private int enforceWritePermission(String callingPkg, Uri uri, IBinder callerToken)
                throws SecurityException {
            final int mode = enforceWritePermissionInner(uri, callingPkg, callerToken);
            if (mode != MODE_ALLOWED) {
                return mode;
            }

            if (mWriteOp != AppOpsManager.OP_NONE) {
                return mAppOpsManager.noteProxyOp(mWriteOp, callingPkg);
            }

            return AppOpsManager.MODE_ALLOWED;
        }
    }

    boolean checkUser(int pid, int uid, Context context) {
        return UserHandle.getUserId(uid) == context.getUserId()
                || mSingleUser
                || context.checkPermission(INTERACT_ACROSS_USERS, pid, uid)
                == PERMISSION_GRANTED;
    }

    
Verify that calling app holds both the given permission and any app-op
associated with that permission.
/**
     * Verify that calling app holds both the given permission and any app-op
     * associated with that permission.
     */
    private int checkPermissionAndAppOp(String permission, String callingPkg,
            IBinder callerToken) {
        if (getContext().checkPermission(permission, Binder.getCallingPid(), Binder.getCallingUid(),
                callerToken) != PERMISSION_GRANTED) {
            return MODE_ERRORED;
        }

        final int permOp = AppOpsManager.permissionToOpCode(permission);
        if (permOp != AppOpsManager.OP_NONE) {
            return mTransport.mAppOpsManager.noteProxyOp(permOp, callingPkg);
        }

        return MODE_ALLOWED;
    }

    
{@hide} /** {@hide} */
    protected int enforceReadPermissionInner(Uri uri, String callingPkg, IBinder callerToken)
            throws SecurityException {
        final Context context = getContext();
        final int pid = Binder.getCallingPid();
        final int uid = Binder.getCallingUid();
        String missingPerm = null;
        int strongestMode = MODE_ALLOWED;

        if (UserHandle.isSameApp(uid, mMyUid)) {
            return MODE_ALLOWED;
        }

        if (mExported && checkUser(pid, uid, context)) {
            final String componentPerm = getReadPermission();
            if (componentPerm != null) {
                final int mode = checkPermissionAndAppOp(componentPerm, callingPkg, callerToken);
                if (mode == MODE_ALLOWED) {
                    return MODE_ALLOWED;
                } else {
                    missingPerm = componentPerm;
                    strongestMode = Math.max(strongestMode, mode);
                }
            }

            // track if unprotected read is allowed; any denied
            // <path-permission> below removes this ability
            boolean allowDefaultRead = (componentPerm == null);

            final PathPermission[] pps = getPathPermissions();
            if (pps != null) {
                final String path = uri.getPath();
                for (PathPermission pp : pps) {
                    final String pathPerm = pp.getReadPermission();
                    if (pathPerm != null && pp.match(path)) {
                        final int mode = checkPermissionAndAppOp(pathPerm, callingPkg, callerToken);
                        if (mode == MODE_ALLOWED) {
                            return MODE_ALLOWED;
                        } else {
                            // any denied <path-permission> means we lose
                            // default <provider> access.
                            allowDefaultRead = false;
                            missingPerm = pathPerm;
                            strongestMode = Math.max(strongestMode, mode);
                        }
                    }
                }
            }

            // if we passed <path-permission> checks above, and no default
            // <provider> permission, then allow access.
            if (allowDefaultRead) return MODE_ALLOWED;
        }

        // last chance, check against any uri grants
        final int callingUserId = UserHandle.getUserId(uid);
        final Uri userUri = (mSingleUser && !UserHandle.isSameUser(mMyUid, uid))
                ? maybeAddUserId(uri, callingUserId) : uri;
        if (context.checkUriPermission(userUri, pid, uid, Intent.FLAG_GRANT_READ_URI_PERMISSION,
                callerToken) == PERMISSION_GRANTED) {
            return MODE_ALLOWED;
        }

        // If the worst denial we found above was ignored, then pass that
        // ignored through; otherwise we assume it should be a real error below.
        if (strongestMode == MODE_IGNORED) {
            return MODE_IGNORED;
        }

        final String suffix;
        if (android.Manifest.permission.MANAGE_DOCUMENTS.equals(mReadPermission)) {
            suffix = " requires that you obtain access using ACTION_OPEN_DOCUMENT or related APIs";
        } else if (mExported) {
            suffix = " requires " + missingPerm + ", or grantUriPermission()";
        } else {
            suffix = " requires the provider be exported, or grantUriPermission()";
        }
        throw new SecurityException("Permission Denial: reading "
                + ContentProvider.this.getClass().getName() + " uri " + uri + " from pid=" + pid
                + ", uid=" + uid + suffix);
    }

    
{@hide} /** {@hide} */
    protected int enforceWritePermissionInner(Uri uri, String callingPkg, IBinder callerToken)
            throws SecurityException {
        final Context context = getContext();
        final int pid = Binder.getCallingPid();
        final int uid = Binder.getCallingUid();
        String missingPerm = null;
        int strongestMode = MODE_ALLOWED;

        if (UserHandle.isSameApp(uid, mMyUid)) {
            return MODE_ALLOWED;
        }

        if (mExported && checkUser(pid, uid, context)) {
            final String componentPerm = getWritePermission();
            if (componentPerm != null) {
                final int mode = checkPermissionAndAppOp(componentPerm, callingPkg, callerToken);
                if (mode == MODE_ALLOWED) {
                    return MODE_ALLOWED;
                } else {
                    missingPerm = componentPerm;
                    strongestMode = Math.max(strongestMode, mode);
                }
            }

            // track if unprotected write is allowed; any denied
            // <path-permission> below removes this ability
            boolean allowDefaultWrite = (componentPerm == null);

            final PathPermission[] pps = getPathPermissions();
            if (pps != null) {
                final String path = uri.getPath();
                for (PathPermission pp : pps) {
                    final String pathPerm = pp.getWritePermission();
                    if (pathPerm != null && pp.match(path)) {
                        final int mode = checkPermissionAndAppOp(pathPerm, callingPkg, callerToken);
                        if (mode == MODE_ALLOWED) {
                            return MODE_ALLOWED;
                        } else {
                            // any denied <path-permission> means we lose
                            // default <provider> access.
                            allowDefaultWrite = false;
                            missingPerm = pathPerm;
                            strongestMode = Math.max(strongestMode, mode);
                        }
                    }
                }
            }

            // if we passed <path-permission> checks above, and no default
            // <provider> permission, then allow access.
            if (allowDefaultWrite) return MODE_ALLOWED;
        }

        // last chance, check against any uri grants
        if (context.checkUriPermission(uri, pid, uid, Intent.FLAG_GRANT_WRITE_URI_PERMISSION,
                callerToken) == PERMISSION_GRANTED) {
            return MODE_ALLOWED;
        }

        // If the worst denial we found above was ignored, then pass that
        // ignored through; otherwise we assume it should be a real error below.
        if (strongestMode == MODE_IGNORED) {
            return MODE_IGNORED;
        }

        final String failReason = mExported
                ? " requires " + missingPerm + ", or grantUriPermission()"
                : " requires the provider be exported, or grantUriPermission()";
        throw new SecurityException("Permission Denial: writing "
                + ContentProvider.this.getClass().getName() + " uri " + uri + " from pid=" + pid
                + ", uid=" + uid + failReason);
    }

    
Retrieves the Context this provider is running in. Only available once onCreate has been called -- this will return null in the constructor. /**
     * Retrieves the Context this provider is running in.  Only available once
     * {@link #onCreate} has been called -- this will return {@code null} in the
     * constructor.
     */
    public final @Nullable Context getContext() {
        return mContext;
    }

    
Set the calling package, returning the current value (or null) which can be used later to restore the previous state. /**
     * Set the calling package, returning the current value (or {@code null})
     * which can be used later to restore the previous state.
     */
    private String setCallingPackage(String callingPackage) {
        final String original = mCallingPackage.get();
        mCallingPackage.set(callingPackage);
        return original;
    }

    
Return the package name of the caller that initiated the request being processed on the current thread. The returned package will have been verified to belong to the calling UID. Returns null if not currently processing a request. 
 This will always return null when processing getType(Uri) or getStreamTypes(Uri, String) requests. 
Throws:
SecurityException – if the calling package doesn't belong to the
            calling UID.
See Also:
Binder.getCallingUid()
Context.grantUriPermission(String, Uri, int)/**
     * Return the package name of the caller that initiated the request being
     * processed on the current thread. The returned package will have been
     * verified to belong to the calling UID. Returns {@code null} if not
     * currently processing a request.
     * <p>
     * This will always return {@code null} when processing
     * {@link #getType(Uri)} or {@link #getStreamTypes(Uri, String)} requests.
     *
     * @see Binder#getCallingUid()
     * @see Context#grantUriPermission(String, Uri, int)
     * @throws SecurityException if the calling package doesn't belong to the
     *             calling UID.
     */
    public final @Nullable String getCallingPackage() {
        final String pkg = mCallingPackage.get();
        if (pkg != null) {
            mTransport.mAppOpsManager.checkPackage(Binder.getCallingUid(), pkg);
        }
        return pkg;
    }

    
Change the authorities of the ContentProvider.
This is normally set for you from its manifest information when the provider is first
created.
Params:
authorities – the semi-colon separated authorities of the ContentProvider.
@hide
/**
     * Change the authorities of the ContentProvider.
     * This is normally set for you from its manifest information when the provider is first
     * created.
     * @hide
     * @param authorities the semi-colon separated authorities of the ContentProvider.
     */
    protected final void setAuthorities(String authorities) {
        if (authorities != null) {
            if (authorities.indexOf(';') == -1) {
                mAuthority = authorities;
                mAuthorities = null;
            } else {
                mAuthority = null;
                mAuthorities = authorities.split(";");
            }
        }
    }

    
@hide
/** @hide */
    protected final boolean matchesOurAuthorities(String authority) {
        if (mAuthority != null) {
            return mAuthority.equals(authority);
        }
        if (mAuthorities != null) {
            int length = mAuthorities.length;
            for (int i = 0; i < length; i++) {
                if (mAuthorities[i].equals(authority)) return true;
            }
        }
        return false;
    }


    
Change the permission required to read data from the content
provider.  This is normally set for you from its manifest information
when the provider is first created.
Params:
permission – Name of the permission required for read-only access./**
     * Change the permission required to read data from the content
     * provider.  This is normally set for you from its manifest information
     * when the provider is first created.
     *
     * @param permission Name of the permission required for read-only access.
     */
    protected final void setReadPermission(@Nullable String permission) {
        mReadPermission = permission;
    }

    
Return the name of the permission required for read-only access to
this content provider.  This method can be called from multiple
threads, as described in
Processes
and Threads.
/**
     * Return the name of the permission required for read-only access to
     * this content provider.  This method can be called from multiple
     * threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     */
    public final @Nullable String getReadPermission() {
        return mReadPermission;
    }

    
Change the permission required to read and write data in the content
provider.  This is normally set for you from its manifest information
when the provider is first created.
Params:
permission – Name of the permission required for read/write access./**
     * Change the permission required to read and write data in the content
     * provider.  This is normally set for you from its manifest information
     * when the provider is first created.
     *
     * @param permission Name of the permission required for read/write access.
     */
    protected final void setWritePermission(@Nullable String permission) {
        mWritePermission = permission;
    }

    
Return the name of the permission required for read/write access to
this content provider.  This method can be called from multiple
threads, as described in
Processes
and Threads.
/**
     * Return the name of the permission required for read/write access to
     * this content provider.  This method can be called from multiple
     * threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     */
    public final @Nullable String getWritePermission() {
        return mWritePermission;
    }

    
Change the path-based permission required to read and/or write data in
the content provider.  This is normally set for you from its manifest
information when the provider is first created.
Params:
permissions – Array of path permission descriptions./**
     * Change the path-based permission required to read and/or write data in
     * the content provider.  This is normally set for you from its manifest
     * information when the provider is first created.
     *
     * @param permissions Array of path permission descriptions.
     */
    protected final void setPathPermissions(@Nullable PathPermission[] permissions) {
        mPathPermissions = permissions;
    }

    
Return the path-based permissions required for read and/or write access to
this content provider.  This method can be called from multiple
threads, as described in
Processes
and Threads.
/**
     * Return the path-based permissions required for read and/or write access to
     * this content provider.  This method can be called from multiple
     * threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     */
    public final @Nullable PathPermission[] getPathPermissions() {
        return mPathPermissions;
    }

    
@hide
/** @hide */
    public final void setAppOps(int readOp, int writeOp) {
        if (!mNoPerms) {
            mTransport.mReadOp = readOp;
            mTransport.mWriteOp = writeOp;
        }
    }

    
@hide
/** @hide */
    public AppOpsManager getAppOpsManager() {
        return mTransport.mAppOpsManager;
    }

    
Implement this to initialize your content provider on startup.
This method is called for all registered content providers on the
application main thread at application launch time.  It must not perform
lengthy operations, or application startup will be delayed.
You should defer nontrivial initialization (such as opening, upgrading, and scanning databases) until the content provider is used (via query, insert, etc). Deferred initialization keeps application startup fast, avoids unnecessary work if the provider turns out not to be needed, and stops database errors (such as a full disk) from halting application launch. 
If you use SQLite, SQLiteOpenHelper is a helpful utility class that makes it easy to manage databases, and will automatically defer opening until first use. If you do use SQLiteOpenHelper, make sure to avoid calling SQLiteOpenHelper.getReadableDatabase or SQLiteOpenHelper.getWritableDatabase from this method. (Instead, override SQLiteOpenHelper.onOpen to initialize the database when it is first opened.) 
Returns:
true if the provider was successfully loaded, false otherwise/**
     * Implement this to initialize your content provider on startup.
     * This method is called for all registered content providers on the
     * application main thread at application launch time.  It must not perform
     * lengthy operations, or application startup will be delayed.
     *
     * <p>You should defer nontrivial initialization (such as opening,
     * upgrading, and scanning databases) until the content provider is used
     * (via {@link #query}, {@link #insert}, etc).  Deferred initialization
     * keeps application startup fast, avoids unnecessary work if the provider
     * turns out not to be needed, and stops database errors (such as a full
     * disk) from halting application launch.
     *
     * <p>If you use SQLite, {@link android.database.sqlite.SQLiteOpenHelper}
     * is a helpful utility class that makes it easy to manage databases,
     * and will automatically defer opening until first use.  If you do use
     * SQLiteOpenHelper, make sure to avoid calling
     * {@link android.database.sqlite.SQLiteOpenHelper#getReadableDatabase} or
     * {@link android.database.sqlite.SQLiteOpenHelper#getWritableDatabase}
     * from this method.  (Instead, override
     * {@link android.database.sqlite.SQLiteOpenHelper#onOpen} to initialize the
     * database when it is first opened.)
     *
     * @return true if the provider was successfully loaded, false otherwise
     */
    public abstract boolean onCreate();

    
{@inheritDoc}
This method is always called on the application main thread, and must
not perform lengthy operations.
The default content provider implementation does nothing.
Override this method to take appropriate action.
(Content providers do not usually care about things like screen
orientation, but may want to know about locale changes.)
/**
     * {@inheritDoc}
     * This method is always called on the application main thread, and must
     * not perform lengthy operations.
     *
     * <p>The default content provider implementation does nothing.
     * Override this method to take appropriate action.
     * (Content providers do not usually care about things like screen
     * orientation, but may want to know about locale changes.)
     */
    @Override
    public void onConfigurationChanged(Configuration newConfig) {
    }

    
{@inheritDoc}
This method is always called on the application main thread, and must
not perform lengthy operations.
The default content provider implementation does nothing.
Subclasses may override this method to take appropriate action.
/**
     * {@inheritDoc}
     * This method is always called on the application main thread, and must
     * not perform lengthy operations.
     *
     * <p>The default content provider implementation does nothing.
     * Subclasses may override this method to take appropriate action.
     */
    @Override
    public void onLowMemory() {
    }

    @Override
    public void onTrimMemory(int level) {
    }

    
Implement this to handle query requests from clients.
Apps targeting VERSION_CODES.O or higher should override query(Uri, String[], Bundle, CancellationSignal) and provide a stub implementation of this method. 
This method can be called from multiple threads, as described in
Processes
and Threads.

Example client call:

// Request a specific record.
Cursor managedCursor = managedQuery(
ContentUris.withAppendedId(Contacts.People.CONTENT_URI, 2),
projection,    // Which columns to return.
null,          // WHERE clause.
null,          // WHERE clause value substitution
People.NAME + " ASC");   // Sort order.
Example implementation:

// SQLiteQueryBuilder is a helper class that creates the
// proper SQL syntax for us.
SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder();
// Set the table we're querying.
qBuilder.setTables(DATABASE_TABLE_NAME);
// If the query ends in a specific record number, we're
// being asked for a specific record, so set the
// WHERE clause in our query.
if((URI_MATCHER.match(uri)) == SPECIFIC_MESSAGE){
qBuilder.appendWhere("_id=" + uri.getPathLeafId());
}
// Make the query.
Cursor c = qBuilder.query(mDb,
projection,
selection,
selectionArgs,
groupBy,
having,
sortOrder);
c.setNotificationUri(getContext().getContentResolver(), uri);
return c;
Params:
uri – The URI to query. This will be the full URI sent by the client;
     if the client is requesting a specific record, the URI will end in a record number
     that the implementation should parse and add to a WHERE or HAVING clause, specifying
     that _id value.
projection – The list of columns to put into the cursor. If null all columns are included.
selection – A selection criteria to apply when filtering rows. If null then all rows are included.
selectionArgs – You may include ?s in selection, which will be replaced by
     the values from selectionArgs, in order that they appear in the selection.
     The values will be bound as Strings.
sortOrder – How the rows in the cursor should be sorted. If null then the provider is free to define the sort order.
Returns:
a Cursor or null./**
     * Implement this to handle query requests from clients.
     *
     * <p>Apps targeting {@link android.os.Build.VERSION_CODES#O} or higher should override
     * {@link #query(Uri, String[], Bundle, CancellationSignal)} and provide a stub
     * implementation of this method.
     *
     * <p>This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     * <p>
     * Example client call:<p>
     * <pre>// Request a specific record.
     * Cursor managedCursor = managedQuery(
                ContentUris.withAppendedId(Contacts.People.CONTENT_URI, 2),
                projection,    // Which columns to return.
                null,          // WHERE clause.
                null,          // WHERE clause value substitution
                People.NAME + " ASC");   // Sort order.</pre>
     * Example implementation:<p>
     * <pre>// SQLiteQueryBuilder is a helper class that creates the
        // proper SQL syntax for us.
        SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder();

        // Set the table we're querying.
        qBuilder.setTables(DATABASE_TABLE_NAME);

        // If the query ends in a specific record number, we're
        // being asked for a specific record, so set the
        // WHERE clause in our query.
        if((URI_MATCHER.match(uri)) == SPECIFIC_MESSAGE){
            qBuilder.appendWhere("_id=" + uri.getPathLeafId());
        }

        // Make the query.
        Cursor c = qBuilder.query(mDb,
                projection,
                selection,
                selectionArgs,
                groupBy,
                having,
                sortOrder);
        c.setNotificationUri(getContext().getContentResolver(), uri);
        return c;</pre>
     *
     * @param uri The URI to query. This will be the full URI sent by the client;
     *      if the client is requesting a specific record, the URI will end in a record number
     *      that the implementation should parse and add to a WHERE or HAVING clause, specifying
     *      that _id value.
     * @param projection The list of columns to put into the cursor. If
     *      {@code null} all columns are included.
     * @param selection A selection criteria to apply when filtering rows.
     *      If {@code null} then all rows are included.
     * @param selectionArgs You may include ?s in selection, which will be replaced by
     *      the values from selectionArgs, in order that they appear in the selection.
     *      The values will be bound as Strings.
     * @param sortOrder How the rows in the cursor should be sorted.
     *      If {@code null} then the provider is free to define the sort order.
     * @return a Cursor or {@code null}.
     */
    public abstract @Nullable Cursor query(@NonNull Uri uri, @Nullable String[] projection,
            @Nullable String selection, @Nullable String[] selectionArgs,
            @Nullable String sortOrder);

    
Implement this to handle query requests from clients with support for cancellation.
Apps targeting VERSION_CODES.O or higher should override query(Uri, String[], Bundle, CancellationSignal) instead of this method. 
This method can be called from multiple threads, as described in
Processes
and Threads.

Example client call:

// Request a specific record.
Cursor managedCursor = managedQuery(
ContentUris.withAppendedId(Contacts.People.CONTENT_URI, 2),
projection,    // Which columns to return.
null,          // WHERE clause.
null,          // WHERE clause value substitution
People.NAME + " ASC");   // Sort order.
Example implementation:

// SQLiteQueryBuilder is a helper class that creates the
// proper SQL syntax for us.
SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder();
// Set the table we're querying.
qBuilder.setTables(DATABASE_TABLE_NAME);
// If the query ends in a specific record number, we're
// being asked for a specific record, so set the
// WHERE clause in our query.
if((URI_MATCHER.match(uri)) == SPECIFIC_MESSAGE){
qBuilder.appendWhere("_id=" + uri.getPathLeafId());
}
// Make the query.
Cursor c = qBuilder.query(mDb,
projection,
selection,
selectionArgs,
groupBy,
having,
sortOrder);
c.setNotificationUri(getContext().getContentResolver(), uri);
return c;
 If you implement this method then you must also implement the version of query(Uri, String[], String, String[], String) that does not take a cancellation signal to ensure correct operation on older versions of the Android Framework in which the cancellation signal overload was not available. 
Params:
uri – The URI to query. This will be the full URI sent by the client;
     if the client is requesting a specific record, the URI will end in a record number
     that the implementation should parse and add to a WHERE or HAVING clause, specifying
     that _id value.
projection – The list of columns to put into the cursor. If null all columns are included.
selection – A selection criteria to apply when filtering rows. If null then all rows are included.
selectionArgs – You may include ?s in selection, which will be replaced by
     the values from selectionArgs, in order that they appear in the selection.
     The values will be bound as Strings.
sortOrder – How the rows in the cursor should be sorted. If null then the provider is free to define the sort order.
cancellationSignal – A signal to cancel the operation in progress, or null if none. If the operation is canceled, then OperationCanceledException will be thrown when the query is executed.
Returns:
a Cursor or null./**
     * Implement this to handle query requests from clients with support for cancellation.
     *
     * <p>Apps targeting {@link android.os.Build.VERSION_CODES#O} or higher should override
     * {@link #query(Uri, String[], Bundle, CancellationSignal)} instead of this method.
     *
     * <p>This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     * <p>
     * Example client call:<p>
     * <pre>// Request a specific record.
     * Cursor managedCursor = managedQuery(
                ContentUris.withAppendedId(Contacts.People.CONTENT_URI, 2),
                projection,    // Which columns to return.
                null,          // WHERE clause.
                null,          // WHERE clause value substitution
                People.NAME + " ASC");   // Sort order.</pre>
     * Example implementation:<p>
     * <pre>// SQLiteQueryBuilder is a helper class that creates the
        // proper SQL syntax for us.
        SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder();

        // Set the table we're querying.
        qBuilder.setTables(DATABASE_TABLE_NAME);

        // If the query ends in a specific record number, we're
        // being asked for a specific record, so set the
        // WHERE clause in our query.
        if((URI_MATCHER.match(uri)) == SPECIFIC_MESSAGE){
            qBuilder.appendWhere("_id=" + uri.getPathLeafId());
        }

        // Make the query.
        Cursor c = qBuilder.query(mDb,
                projection,
                selection,
                selectionArgs,
                groupBy,
                having,
                sortOrder);
        c.setNotificationUri(getContext().getContentResolver(), uri);
        return c;</pre>
     * <p>
     * If you implement this method then you must also implement the version of
     * {@link #query(Uri, String[], String, String[], String)} that does not take a cancellation
     * signal to ensure correct operation on older versions of the Android Framework in
     * which the cancellation signal overload was not available.
     *
     * @param uri The URI to query. This will be the full URI sent by the client;
     *      if the client is requesting a specific record, the URI will end in a record number
     *      that the implementation should parse and add to a WHERE or HAVING clause, specifying
     *      that _id value.
     * @param projection The list of columns to put into the cursor. If
     *      {@code null} all columns are included.
     * @param selection A selection criteria to apply when filtering rows.
     *      If {@code null} then all rows are included.
     * @param selectionArgs You may include ?s in selection, which will be replaced by
     *      the values from selectionArgs, in order that they appear in the selection.
     *      The values will be bound as Strings.
     * @param sortOrder How the rows in the cursor should be sorted.
     *      If {@code null} then the provider is free to define the sort order.
     * @param cancellationSignal A signal to cancel the operation in progress, or {@code null} if none.
     * If the operation is canceled, then {@link android.os.OperationCanceledException} will be thrown
     * when the query is executed.
     * @return a Cursor or {@code null}.
     */
    public @Nullable Cursor query(@NonNull Uri uri, @Nullable String[] projection,
            @Nullable String selection, @Nullable String[] selectionArgs,
            @Nullable String sortOrder, @Nullable CancellationSignal cancellationSignal) {
        return query(uri, projection, selection, selectionArgs, sortOrder);
    }

    
Implement this to handle query requests where the arguments are packed into a Bundle. Arguments may include traditional SQL style query arguments. When present these should be handled according to the contract established in 
Traditional SQL arguments can be found in the bundle using the following keys:
ContentResolver.QUERY_ARG_SQL_SELECTION 
ContentResolver.QUERY_ARG_SQL_SELECTION_ARGS 
ContentResolver.QUERY_ARG_SQL_SORT_ORDER 
This method can be called from multiple threads, as described in
Processes
and Threads.

Example client call:

// Request 20 records starting at row index 30.
Bundle queryArgs = new Bundle();
queryArgs.putInt(ContentResolver.QUERY_ARG_OFFSET, 30);
queryArgs.putInt(ContentResolver.QUERY_ARG_LIMIT, 20);
Cursor cursor = getContentResolver().query(
contentUri,    // Content Uri is specific to individual content providers.
projection,    // String[] describing which columns to return.
queryArgs,     // Query arguments.
null);         // Cancellation signal.
Example implementation:

int recordsetSize = 0x1000;  // Actual value is implementation specific.
queryArgs = queryArgs != null ? queryArgs : Bundle.EMPTY;  // ensure queryArgs is non-null
int offset = queryArgs.getInt(ContentResolver.QUERY_ARG_OFFSET, 0);
int limit = queryArgs.getInt(ContentResolver.QUERY_ARG_LIMIT, Integer.MIN_VALUE);
MatrixCursor c = new MatrixCursor(PROJECTION, limit);
// Calculate the number of items to include in the cursor.
int numItems = MathUtils.constrain(recordsetSize - offset, 0, limit);
// Build the paged result set....
for (int i = offset; i < offset + numItems; i++) {
// populate row from your data.
}
Bundle extras = new Bundle();
c.setExtras(extras);
// Any QUERY_ARG_* key may be included if honored.
// In an actual implementation, include only keys that are both present in queryArgs
// and reflected in the Cursor output. For example, if QUERY_ARG_OFFSET were included
// in queryArgs, but was ignored because it contained an invalid value (like –273),
// then QUERY_ARG_OFFSET should be omitted.
extras.putStringArray(ContentResolver.EXTRA_HONORED_ARGS, new String[] {
ContentResolver.QUERY_ARG_OFFSET,
ContentResolver.QUERY_ARG_LIMIT
});
extras.putInt(ContentResolver.EXTRA_TOTAL_COUNT, recordsetSize);
cursor.setNotificationUri(getContext().getContentResolver(), uri);
return cursor;

Params:
uri – The URI to query. This will be the full URI sent by the client.
projection – The list of columns to put into the cursor. If null provide a default set of columns.
queryArgs – A Bundle containing all additional information necessary for the query.
           Values in the Bundle may include SQL style arguments.
cancellationSignal – A signal to cancel the operation in progress, or null.
See Also:
for
    implementation details.
Returns:
a Cursor or null./**
     * Implement this to handle query requests where the arguments are packed into a {@link Bundle}.
     * Arguments may include traditional SQL style query arguments. When present these
     * should be handled  according to the contract established in
     * {@link #query(Uri, String[], String, String[], String, CancellationSignal).
     *
     * <p>Traditional SQL arguments can be found in the bundle using the following keys:
     * <li>{@link ContentResolver#QUERY_ARG_SQL_SELECTION}
     * <li>{@link ContentResolver#QUERY_ARG_SQL_SELECTION_ARGS}
     * <li>{@link ContentResolver#QUERY_ARG_SQL_SORT_ORDER}
     *
     * <p>This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     *
     * <p>
     * Example client call:<p>
     * <pre>// Request 20 records starting at row index 30.
       Bundle queryArgs = new Bundle();
       queryArgs.putInt(ContentResolver.QUERY_ARG_OFFSET, 30);
       queryArgs.putInt(ContentResolver.QUERY_ARG_LIMIT, 20);

       Cursor cursor = getContentResolver().query(
                contentUri,    // Content Uri is specific to individual content providers.
                projection,    // String[] describing which columns to return.
                queryArgs,     // Query arguments.
                null);         // Cancellation signal.</pre>
     *
     * Example implementation:<p>
     * <pre>

        int recordsetSize = 0x1000;  // Actual value is implementation specific.
        queryArgs = queryArgs != null ? queryArgs : Bundle.EMPTY;  // ensure queryArgs is non-null

        int offset = queryArgs.getInt(ContentResolver.QUERY_ARG_OFFSET, 0);
        int limit = queryArgs.getInt(ContentResolver.QUERY_ARG_LIMIT, Integer.MIN_VALUE);

        MatrixCursor c = new MatrixCursor(PROJECTION, limit);

        // Calculate the number of items to include in the cursor.
        int numItems = MathUtils.constrain(recordsetSize - offset, 0, limit);

        // Build the paged result set....
        for (int i = offset; i < offset + numItems; i++) {
            // populate row from your data.
        }

        Bundle extras = new Bundle();
        c.setExtras(extras);

        // Any QUERY_ARG_* key may be included if honored.
        // In an actual implementation, include only keys that are both present in queryArgs
        // and reflected in the Cursor output. For example, if QUERY_ARG_OFFSET were included
        // in queryArgs, but was ignored because it contained an invalid value (like –273),
        // then QUERY_ARG_OFFSET should be omitted.
        extras.putStringArray(ContentResolver.EXTRA_HONORED_ARGS, new String[] {
            ContentResolver.QUERY_ARG_OFFSET,
            ContentResolver.QUERY_ARG_LIMIT
        });

        extras.putInt(ContentResolver.EXTRA_TOTAL_COUNT, recordsetSize);

        cursor.setNotificationUri(getContext().getContentResolver(), uri);

        return cursor;</pre>
     * <p>
     * @see #query(Uri, String[], String, String[], String, CancellationSignal) for
     *     implementation details.
     *
     * @param uri The URI to query. This will be the full URI sent by the client.
     * @param projection The list of columns to put into the cursor.
     *            If {@code null} provide a default set of columns.
     * @param queryArgs A Bundle containing all additional information necessary for the query.
     *            Values in the Bundle may include SQL style arguments.
     * @param cancellationSignal A signal to cancel the operation in progress,
     *            or {@code null}.
     * @return a Cursor or {@code null}.
     */
    public @Nullable Cursor query(@NonNull Uri uri, @Nullable String[] projection,
            @Nullable Bundle queryArgs, @Nullable CancellationSignal cancellationSignal) {
        queryArgs = queryArgs != null ? queryArgs : Bundle.EMPTY;

        // if client doesn't supply an SQL sort order argument, attempt to build one from
        // QUERY_ARG_SORT* arguments.
        String sortClause = queryArgs.getString(ContentResolver.QUERY_ARG_SQL_SORT_ORDER);
        if (sortClause == null && queryArgs.containsKey(ContentResolver.QUERY_ARG_SORT_COLUMNS)) {
            sortClause = ContentResolver.createSqlSortClause(queryArgs);
        }

        return query(
                uri,
                projection,
                queryArgs.getString(ContentResolver.QUERY_ARG_SQL_SELECTION),
                queryArgs.getStringArray(ContentResolver.QUERY_ARG_SQL_SELECTION_ARGS),
                sortClause,
                cancellationSignal);
    }

    
Implement this to handle requests for the MIME type of the data at the
given URI.  The returned MIME type should start with
vnd.android.cursor.item for a single record,
or vnd.android.cursor.dir/ for multiple items.
This method can be called from multiple threads, as described in
Processes
and Threads.
Note that there are no permissions needed for an application to
access this information; if your content provider requires read and/or
write permissions, or is not exported, all applications can still call
this method regardless of their access permissions.  This allows them
to retrieve the MIME type for a URI when dispatching intents.
Params:
uri – the URI to query.
Returns:
a MIME type string, or null if there is no type./**
     * Implement this to handle requests for the MIME type of the data at the
     * given URI.  The returned MIME type should start with
     * <code>vnd.android.cursor.item</code> for a single record,
     * or <code>vnd.android.cursor.dir/</code> for multiple items.
     * This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     *
     * <p>Note that there are no permissions needed for an application to
     * access this information; if your content provider requires read and/or
     * write permissions, or is not exported, all applications can still call
     * this method regardless of their access permissions.  This allows them
     * to retrieve the MIME type for a URI when dispatching intents.
     *
     * @param uri the URI to query.
     * @return a MIME type string, or {@code null} if there is no type.
     */
    public abstract @Nullable String getType(@NonNull Uri uri);

    
Implement this to support canonicalization of URIs that refer to your
content provider.  A canonical URI is one that can be transported across
devices, backup/restore, and other contexts, and still be able to refer
to the same data item.  Typically this is implemented by adding query
params to the URI allowing the content provider to verify that an incoming
canonical URI references the same data as it was originally intended for and,
if it doesn't, to find that data (if it exists) in the current environment.
For example, if the content provider holds people and a normal URI in it
is created with a row index into that people database, the cananical representation
may have an additional query param at the end which specifies the name of the
person it is intended for.  Later calls into the provider with that URI will look
up the row of that URI's base index and, if it doesn't match or its entry's
name doesn't match the name in the query param, perform a query on its database
to find the correct row to operate on.
If you implement support for canonical URIs, all incoming calls with URIs (including this one) must perform this verification and recovery of any canonical URIs they receive. In addition, you must also implement uncanonicalize to strip the canonicalization of any of these URIs.
The default implementation of this method returns null, indicating that
canonical URIs are not supported.
Params:
url – The Uri to canonicalize.
Returns:
Return the canonical representation of url, or null if
canonicalization of that Uri is not supported./**
     * Implement this to support canonicalization of URIs that refer to your
     * content provider.  A canonical URI is one that can be transported across
     * devices, backup/restore, and other contexts, and still be able to refer
     * to the same data item.  Typically this is implemented by adding query
     * params to the URI allowing the content provider to verify that an incoming
     * canonical URI references the same data as it was originally intended for and,
     * if it doesn't, to find that data (if it exists) in the current environment.
     *
     * <p>For example, if the content provider holds people and a normal URI in it
     * is created with a row index into that people database, the cananical representation
     * may have an additional query param at the end which specifies the name of the
     * person it is intended for.  Later calls into the provider with that URI will look
     * up the row of that URI's base index and, if it doesn't match or its entry's
     * name doesn't match the name in the query param, perform a query on its database
     * to find the correct row to operate on.</p>
     *
     * <p>If you implement support for canonical URIs, <b>all</b> incoming calls with
     * URIs (including this one) must perform this verification and recovery of any
     * canonical URIs they receive.  In addition, you must also implement
     * {@link #uncanonicalize} to strip the canonicalization of any of these URIs.</p>
     *
     * <p>The default implementation of this method returns null, indicating that
     * canonical URIs are not supported.</p>
     *
     * @param url The Uri to canonicalize.
     *
     * @return Return the canonical representation of <var>url</var>, or null if
     * canonicalization of that Uri is not supported.
     */
    public @Nullable Uri canonicalize(@NonNull Uri url) {
        return null;
    }

    
Remove canonicalization from canonical URIs previously returned by canonicalize. For example, if your implementation is to add a query param to canonicalize a URI, this method can simply trip any query params on the URI. The default implementation always returns the same url that was passed in.
Params:
url – The Uri to remove any canonicalization from.
Returns:
Return the non-canonical representation of url, return
the url as-is if there is nothing to do, or return null if
the data identified by the canonical representation can not be found in
the current environment./**
     * Remove canonicalization from canonical URIs previously returned by
     * {@link #canonicalize}.  For example, if your implementation is to add
     * a query param to canonicalize a URI, this method can simply trip any
     * query params on the URI.  The default implementation always returns the
     * same <var>url</var> that was passed in.
     *
     * @param url The Uri to remove any canonicalization from.
     *
     * @return Return the non-canonical representation of <var>url</var>, return
     * the <var>url</var> as-is if there is nothing to do, or return null if
     * the data identified by the canonical representation can not be found in
     * the current environment.
     */
    public @Nullable Uri uncanonicalize(@NonNull Uri url) {
        return url;
    }

    
Implement this to support refresh of content identified by uri. By default, this method returns false; providers who wish to implement this should return true to signal the client that the provider has tried refreshing with its own implementation. 
 This allows clients to request an explicit refresh of content identified by uri. 

Client code should only invoke this method when there is a strong indication (such as a user
initiated pull to refresh gesture) that the content is stale.
 Remember to send ContentResolver.notifyChange(Uri, ContentObserver) notifications when content changes. 
Params:
uri – The Uri identifying the data to refresh.
args – Additional options from the client. The definitions of these are specific to the
           content provider being called.
cancellationSignal – A signal to cancel the operation in progress, or null if none. For example, if you called refresh on a particular uri, you should call CancellationSignal.throwIfCanceled() to check whether the client has canceled the refresh request.
Returns:
true if the provider actually tried refreshing./**
     * Implement this to support refresh of content identified by {@code uri}. By default, this
     * method returns false; providers who wish to implement this should return true to signal the
     * client that the provider has tried refreshing with its own implementation.
     * <p>
     * This allows clients to request an explicit refresh of content identified by {@code uri}.
     * <p>
     * Client code should only invoke this method when there is a strong indication (such as a user
     * initiated pull to refresh gesture) that the content is stale.
     * <p>
     * Remember to send {@link ContentResolver#notifyChange(Uri, android.database.ContentObserver)}
     * notifications when content changes.
     *
     * @param uri The Uri identifying the data to refresh.
     * @param args Additional options from the client. The definitions of these are specific to the
     *            content provider being called.
     * @param cancellationSignal A signal to cancel the operation in progress, or {@code null} if
     *            none. For example, if you called refresh on a particular uri, you should call
     *            {@link CancellationSignal#throwIfCanceled()} to check whether the client has
     *            canceled the refresh request.
     * @return true if the provider actually tried refreshing.
     */
    public boolean refresh(Uri uri, @Nullable Bundle args,
            @Nullable CancellationSignal cancellationSignal) {
        return false;
    }

    
@hide
 Implementation when a caller has performed an insert on the content provider, but that call has been rejected for the operation given to setAppOps(int, int). The default implementation simply returns a dummy URI that is the base URI with a 0 path element appended./**
     * @hide
     * Implementation when a caller has performed an insert on the content
     * provider, but that call has been rejected for the operation given
     * to {@link #setAppOps(int, int)}.  The default implementation simply
     * returns a dummy URI that is the base URI with a 0 path element
     * appended.
     */
    public Uri rejectInsert(Uri uri, ContentValues values) {
        // If not allowed, we need to return some reasonable URI.  Maybe the
        // content provider should be responsible for this, but for now we
        // will just return the base URI with a dummy '0' tagged on to it.
        // You shouldn't be able to read if you can't write, anyway, so it
        // shouldn't matter much what is returned.
        return uri.buildUpon().appendPath("0").build();
    }

    
Implement this to handle requests to insert a new row. As a courtesy, call notifyChange() after inserting. This method can be called from multiple threads, as described in Processes
and Threads.
Params:
uri – The content:// URI of the insertion request. This must not be null.
values – A set of column_name/value pairs to add to the database. This must not be null.
Returns:
The URI for the newly inserted item./**
     * Implement this to handle requests to insert a new row.
     * As a courtesy, call {@link ContentResolver#notifyChange(android.net.Uri ,android.database.ContentObserver) notifyChange()}
     * after inserting.
     * This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     * @param uri The content:// URI of the insertion request. This must not be {@code null}.
     * @param values A set of column_name/value pairs to add to the database.
     *     This must not be {@code null}.
     * @return The URI for the newly inserted item.
     */
    public abstract @Nullable Uri insert(@NonNull Uri uri, @Nullable ContentValues values);

    
Override this to handle requests to insert a set of new rows, or the default implementation will iterate over the values and call insert on each of them. As a courtesy, call notifyChange() after inserting. This method can be called from multiple threads, as described in Processes
and Threads.
Params:
uri – The content:// URI of the insertion request.
values – An array of sets of column_name/value pairs to add to the database. This must not be null.
Returns:
The number of values that were inserted./**
     * Override this to handle requests to insert a set of new rows, or the
     * default implementation will iterate over the values and call
     * {@link #insert} on each of them.
     * As a courtesy, call {@link ContentResolver#notifyChange(android.net.Uri ,android.database.ContentObserver) notifyChange()}
     * after inserting.
     * This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     *
     * @param uri The content:// URI of the insertion request.
     * @param values An array of sets of column_name/value pairs to add to the database.
     *    This must not be {@code null}.
     * @return The number of values that were inserted.
     */
    public int bulkInsert(@NonNull Uri uri, @NonNull ContentValues[] values) {
        int numValues = values.length;
        for (int i = 0; i < numValues; i++) {
            insert(uri, values[i]);
        }
        return numValues;
    }

    
Implement this to handle requests to delete one or more rows. The implementation should apply the selection clause when performing deletion, allowing the operation to affect multiple rows in a directory. As a courtesy, call notifyChange() after deleting. This method can be called from multiple threads, as described in Processes
and Threads.
The implementation is responsible for parsing out a row ID at the end
of the URI, if a specific row is being deleted. That is, the client would
pass in content://contacts/people/22 and the implementation is
responsible for parsing the record number (22) when creating a SQL statement.
Params:
uri – The full URI to query, including a row ID (if a specific record is requested).
selection – An optional restriction to apply to rows when deleting.
Throws:
SQLException – 
Returns:
The number of rows affected./**
     * Implement this to handle requests to delete one or more rows.
     * The implementation should apply the selection clause when performing
     * deletion, allowing the operation to affect multiple rows in a directory.
     * As a courtesy, call {@link ContentResolver#notifyChange(android.net.Uri ,android.database.ContentObserver) notifyChange()}
     * after deleting.
     * This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     *
     * <p>The implementation is responsible for parsing out a row ID at the end
     * of the URI, if a specific row is being deleted. That is, the client would
     * pass in <code>content://contacts/people/22</code> and the implementation is
     * responsible for parsing the record number (22) when creating a SQL statement.
     *
     * @param uri The full URI to query, including a row ID (if a specific record is requested).
     * @param selection An optional restriction to apply to rows when deleting.
     * @return The number of rows affected.
     * @throws SQLException
     */
    public abstract int delete(@NonNull Uri uri, @Nullable String selection,
            @Nullable String[] selectionArgs);

    
Implement this to handle requests to update one or more rows. The implementation should update all rows matching the selection to set the columns according to the provided values map. As a courtesy, call notifyChange() after updating. This method can be called from multiple threads, as described in Processes
and Threads.
Params:
uri – The URI to query. This can potentially have a record ID if this
is an update request for a specific record.
values – A set of column_name/value pairs to update in the database. This must not be null.
selection – An optional filter to match rows to update.
Returns:
the number of rows affected./**
     * Implement this to handle requests to update one or more rows.
     * The implementation should update all rows matching the selection
     * to set the columns according to the provided values map.
     * As a courtesy, call {@link ContentResolver#notifyChange(android.net.Uri ,android.database.ContentObserver) notifyChange()}
     * after updating.
     * This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     *
     * @param uri The URI to query. This can potentially have a record ID if this
     * is an update request for a specific record.
     * @param values A set of column_name/value pairs to update in the database.
     *     This must not be {@code null}.
     * @param selection An optional filter to match rows to update.
     * @return the number of rows affected.
     */
    public abstract int update(@NonNull Uri uri, @Nullable ContentValues values,
            @Nullable String selection, @Nullable String[] selectionArgs);

    
Override this to handle requests to open a file blob. The default implementation always throws FileNotFoundException. This method can be called from multiple threads, as described in Processes
and Threads.
This method returns a ParcelFileDescriptor, which is returned directly
to the caller.  This way large data (such as images and documents) can be
returned without copying the content.
The returned ParcelFileDescriptor is owned by the caller, so it is
their responsibility to close it when done.  That is, the implementation
of this method should create a new ParcelFileDescriptor for each call.

If opened with the exclusive "r" or "w" modes, the returned
ParcelFileDescriptor can be a pipe or socket pair to enable streaming
of data. Opening with the "rw" or "rwt" modes implies a file on disk that
supports seeking.
 If you need to detect when the returned ParcelFileDescriptor has been closed, or if the remote process has crashed or encountered some other error, you can use ParcelFileDescriptor.open(File, int, Handler, OnCloseListener), ParcelFileDescriptor.createReliablePipe(), or ParcelFileDescriptor.createReliableSocketPair(). 
 If you need to return a large file that isn't backed by a real file on disk, such as a file on a network share or cloud storage service, consider using StorageManager.openProxyFileDescriptor(int, ProxyFileDescriptorCallback, Handler) which will let you to stream the content on-demand. 
For use in Intents, you will want to implement getType to return the appropriate MIME type for the data returned here with the same URI. This will allow intent resolution to automatically determine the data MIME type and select the appropriate matching targets as part of its operation.
For better interoperability with other applications, it is recommended that for any URIs that can be opened, you also support queries on them containing at least the columns specified by OpenableColumns. You may also want to support other common columns if you have additional meta-data to supply, such as MediaColumns.DATE_ADDED in MediaColumns.
Params:
uri – The URI whose file is to be opened.
mode – Access mode for the file.  May be "r" for read-only access,
"rw" for read and write access, or "rwt" for read and write access
that truncates any existing file.
Throws:
FileNotFoundException – Throws FileNotFoundException if there is
no file associated with the given URI or the mode is invalid.
SecurityException – Throws SecurityException if the caller does
not have permission to access the file.
See Also:
openAssetFile(Uri, String)
openFileHelper(Uri, String)
getType(Uri)
ParcelFileDescriptor.parseMode(String)
Returns:
Returns a new ParcelFileDescriptor which you can use to access
the file./**
     * Override this to handle requests to open a file blob.
     * The default implementation always throws {@link FileNotFoundException}.
     * This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     *
     * <p>This method returns a ParcelFileDescriptor, which is returned directly
     * to the caller.  This way large data (such as images and documents) can be
     * returned without copying the content.
     *
     * <p>The returned ParcelFileDescriptor is owned by the caller, so it is
     * their responsibility to close it when done.  That is, the implementation
     * of this method should create a new ParcelFileDescriptor for each call.
     * <p>
     * If opened with the exclusive "r" or "w" modes, the returned
     * ParcelFileDescriptor can be a pipe or socket pair to enable streaming
     * of data. Opening with the "rw" or "rwt" modes implies a file on disk that
     * supports seeking.
     * <p>
     * If you need to detect when the returned ParcelFileDescriptor has been
     * closed, or if the remote process has crashed or encountered some other
     * error, you can use {@link ParcelFileDescriptor#open(File, int,
     * android.os.Handler, android.os.ParcelFileDescriptor.OnCloseListener)},
     * {@link ParcelFileDescriptor#createReliablePipe()}, or
     * {@link ParcelFileDescriptor#createReliableSocketPair()}.
     * <p>
     * If you need to return a large file that isn't backed by a real file on
     * disk, such as a file on a network share or cloud storage service,
     * consider using
     * {@link StorageManager#openProxyFileDescriptor(int, android.os.ProxyFileDescriptorCallback, android.os.Handler)}
     * which will let you to stream the content on-demand.
     *
     * <p class="note">For use in Intents, you will want to implement {@link #getType}
     * to return the appropriate MIME type for the data returned here with
     * the same URI.  This will allow intent resolution to automatically determine the data MIME
     * type and select the appropriate matching targets as part of its operation.</p>
     *
     * <p class="note">For better interoperability with other applications, it is recommended
     * that for any URIs that can be opened, you also support queries on them
     * containing at least the columns specified by {@link android.provider.OpenableColumns}.
     * You may also want to support other common columns if you have additional meta-data
     * to supply, such as {@link android.provider.MediaStore.MediaColumns#DATE_ADDED}
     * in {@link android.provider.MediaStore.MediaColumns}.</p>
     *
     * @param uri The URI whose file is to be opened.
     * @param mode Access mode for the file.  May be "r" for read-only access,
     * "rw" for read and write access, or "rwt" for read and write access
     * that truncates any existing file.
     *
     * @return Returns a new ParcelFileDescriptor which you can use to access
     * the file.
     *
     * @throws FileNotFoundException Throws FileNotFoundException if there is
     * no file associated with the given URI or the mode is invalid.
     * @throws SecurityException Throws SecurityException if the caller does
     * not have permission to access the file.
     *
     * @see #openAssetFile(Uri, String)
     * @see #openFileHelper(Uri, String)
     * @see #getType(android.net.Uri)
     * @see ParcelFileDescriptor#parseMode(String)
     */
    public @Nullable ParcelFileDescriptor openFile(@NonNull Uri uri, @NonNull String mode)
            throws FileNotFoundException {
        throw new FileNotFoundException("No files supported by provider at "
                + uri);
    }

    
Override this to handle requests to open a file blob. The default implementation always throws FileNotFoundException. This method can be called from multiple threads, as described in Processes
and Threads.
This method returns a ParcelFileDescriptor, which is returned directly
to the caller.  This way large data (such as images and documents) can be
returned without copying the content.
The returned ParcelFileDescriptor is owned by the caller, so it is
their responsibility to close it when done.  That is, the implementation
of this method should create a new ParcelFileDescriptor for each call.

If opened with the exclusive "r" or "w" modes, the returned
ParcelFileDescriptor can be a pipe or socket pair to enable streaming
of data. Opening with the "rw" or "rwt" modes implies a file on disk that
supports seeking.
 If you need to detect when the returned ParcelFileDescriptor has been closed, or if the remote process has crashed or encountered some other error, you can use ParcelFileDescriptor.open(File, int, Handler, OnCloseListener), ParcelFileDescriptor.createReliablePipe(), or ParcelFileDescriptor.createReliableSocketPair(). 
For use in Intents, you will want to implement getType to return the appropriate MIME type for the data returned here with the same URI. This will allow intent resolution to automatically determine the data MIME type and select the appropriate matching targets as part of its operation.
For better interoperability with other applications, it is recommended that for any URIs that can be opened, you also support queries on them containing at least the columns specified by OpenableColumns. You may also want to support other common columns if you have additional meta-data to supply, such as MediaColumns.DATE_ADDED in MediaColumns.
Params:
uri – The URI whose file is to be opened.
mode – Access mode for the file. May be "r" for read-only access,
           "w" for write-only access, "rw" for read and write access, or
           "rwt" for read and write access that truncates any existing
           file.
signal – A signal to cancel the operation in progress, or null if none. For example, if you are downloading a file from the network to service a "rw" mode request, you should periodically call CancellationSignal.throwIfCanceled() to check whether the client has canceled the request and abort the download.
Throws:
FileNotFoundException – Throws FileNotFoundException if there is
no file associated with the given URI or the mode is invalid.
SecurityException – Throws SecurityException if the caller does
not have permission to access the file.
See Also:
openAssetFile(Uri, String)
openFileHelper(Uri, String)
getType(Uri)
ParcelFileDescriptor.parseMode(String)
Returns:
Returns a new ParcelFileDescriptor which you can use to access
the file./**
     * Override this to handle requests to open a file blob.
     * The default implementation always throws {@link FileNotFoundException}.
     * This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     *
     * <p>This method returns a ParcelFileDescriptor, which is returned directly
     * to the caller.  This way large data (such as images and documents) can be
     * returned without copying the content.
     *
     * <p>The returned ParcelFileDescriptor is owned by the caller, so it is
     * their responsibility to close it when done.  That is, the implementation
     * of this method should create a new ParcelFileDescriptor for each call.
     * <p>
     * If opened with the exclusive "r" or "w" modes, the returned
     * ParcelFileDescriptor can be a pipe or socket pair to enable streaming
     * of data. Opening with the "rw" or "rwt" modes implies a file on disk that
     * supports seeking.
     * <p>
     * If you need to detect when the returned ParcelFileDescriptor has been
     * closed, or if the remote process has crashed or encountered some other
     * error, you can use {@link ParcelFileDescriptor#open(File, int,
     * android.os.Handler, android.os.ParcelFileDescriptor.OnCloseListener)},
     * {@link ParcelFileDescriptor#createReliablePipe()}, or
     * {@link ParcelFileDescriptor#createReliableSocketPair()}.
     *
     * <p class="note">For use in Intents, you will want to implement {@link #getType}
     * to return the appropriate MIME type for the data returned here with
     * the same URI.  This will allow intent resolution to automatically determine the data MIME
     * type and select the appropriate matching targets as part of its operation.</p>
     *
     * <p class="note">For better interoperability with other applications, it is recommended
     * that for any URIs that can be opened, you also support queries on them
     * containing at least the columns specified by {@link android.provider.OpenableColumns}.
     * You may also want to support other common columns if you have additional meta-data
     * to supply, such as {@link android.provider.MediaStore.MediaColumns#DATE_ADDED}
     * in {@link android.provider.MediaStore.MediaColumns}.</p>
     *
     * @param uri The URI whose file is to be opened.
     * @param mode Access mode for the file. May be "r" for read-only access,
     *            "w" for write-only access, "rw" for read and write access, or
     *            "rwt" for read and write access that truncates any existing
     *            file.
     * @param signal A signal to cancel the operation in progress, or
     *            {@code null} if none. For example, if you are downloading a
     *            file from the network to service a "rw" mode request, you
     *            should periodically call
     *            {@link CancellationSignal#throwIfCanceled()} to check whether
     *            the client has canceled the request and abort the download.
     *
     * @return Returns a new ParcelFileDescriptor which you can use to access
     * the file.
     *
     * @throws FileNotFoundException Throws FileNotFoundException if there is
     * no file associated with the given URI or the mode is invalid.
     * @throws SecurityException Throws SecurityException if the caller does
     * not have permission to access the file.
     *
     * @see #openAssetFile(Uri, String)
     * @see #openFileHelper(Uri, String)
     * @see #getType(android.net.Uri)
     * @see ParcelFileDescriptor#parseMode(String)
     */
    public @Nullable ParcelFileDescriptor openFile(@NonNull Uri uri, @NonNull String mode,
            @Nullable CancellationSignal signal) throws FileNotFoundException {
        return openFile(uri, mode);
    }

    
This is like openFile, but can be implemented by providers that need to be able to return sub-sections of files, often assets inside of their .apk. This method can be called from multiple threads, as described in Processes
and Threads.
If you implement this, your clients must be able to deal with such file slices, either directly with ContentResolver.openAssetFileDescriptor, or by using the higher-level ContentResolver.openInputStream or ContentResolver.openOutputStream methods. 

The returned AssetFileDescriptor can be a pipe or socket pair to enable
streaming of data.
If you are implementing this to return a full file, you should create the AssetFileDescriptor with AssetFileDescriptor.UNKNOWN_LENGTH to be compatible with applications that cannot handle sub-sections of files.
For use in Intents, you will want to implement getType to return the appropriate MIME type for the data returned here with the same URI. This will allow intent resolution to automatically determine the data MIME type and select the appropriate matching targets as part of its operation.
For better interoperability with other applications, it is recommended that for any URIs that can be opened, you also support queries on them containing at least the columns specified by OpenableColumns.
Params:
uri – The URI whose file is to be opened.
mode – Access mode for the file.  May be "r" for read-only access,
"w" for write-only access (erasing whatever data is currently in
the file), "wa" for write-only access to append to any existing data,
"rw" for read and write access on any existing data, and "rwt" for read
and write access that truncates any existing file.
Throws:
FileNotFoundException – Throws FileNotFoundException if there is
no file associated with the given URI or the mode is invalid.
SecurityException – Throws SecurityException if the caller does
not have permission to access the file.
See Also:
openFile(Uri, String)
openFileHelper(Uri, String)
getType(Uri)
Returns:
Returns a new AssetFileDescriptor which you can use to access
the file./**
     * This is like {@link #openFile}, but can be implemented by providers
     * that need to be able to return sub-sections of files, often assets
     * inside of their .apk.
     * This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     *
     * <p>If you implement this, your clients must be able to deal with such
     * file slices, either directly with
     * {@link ContentResolver#openAssetFileDescriptor}, or by using the higher-level
     * {@link ContentResolver#openInputStream ContentResolver.openInputStream}
     * or {@link ContentResolver#openOutputStream ContentResolver.openOutputStream}
     * methods.
     * <p>
     * The returned AssetFileDescriptor can be a pipe or socket pair to enable
     * streaming of data.
     *
     * <p class="note">If you are implementing this to return a full file, you
     * should create the AssetFileDescriptor with
     * {@link AssetFileDescriptor#UNKNOWN_LENGTH} to be compatible with
     * applications that cannot handle sub-sections of files.</p>
     *
     * <p class="note">For use in Intents, you will want to implement {@link #getType}
     * to return the appropriate MIME type for the data returned here with
     * the same URI.  This will allow intent resolution to automatically determine the data MIME
     * type and select the appropriate matching targets as part of its operation.</p>
     *
     * <p class="note">For better interoperability with other applications, it is recommended
     * that for any URIs that can be opened, you also support queries on them
     * containing at least the columns specified by {@link android.provider.OpenableColumns}.</p>
     *
     * @param uri The URI whose file is to be opened.
     * @param mode Access mode for the file.  May be "r" for read-only access,
     * "w" for write-only access (erasing whatever data is currently in
     * the file), "wa" for write-only access to append to any existing data,
     * "rw" for read and write access on any existing data, and "rwt" for read
     * and write access that truncates any existing file.
     *
     * @return Returns a new AssetFileDescriptor which you can use to access
     * the file.
     *
     * @throws FileNotFoundException Throws FileNotFoundException if there is
     * no file associated with the given URI or the mode is invalid.
     * @throws SecurityException Throws SecurityException if the caller does
     * not have permission to access the file.
     *
     * @see #openFile(Uri, String)
     * @see #openFileHelper(Uri, String)
     * @see #getType(android.net.Uri)
     */
    public @Nullable AssetFileDescriptor openAssetFile(@NonNull Uri uri, @NonNull String mode)
            throws FileNotFoundException {
        ParcelFileDescriptor fd = openFile(uri, mode);
        return fd != null ? new AssetFileDescriptor(fd, 0, -1) : null;
    }

    
This is like openFile, but can be implemented by providers that need to be able to return sub-sections of files, often assets inside of their .apk. This method can be called from multiple threads, as described in Processes
and Threads.
If you implement this, your clients must be able to deal with such file slices, either directly with ContentResolver.openAssetFileDescriptor, or by using the higher-level ContentResolver.openInputStream or ContentResolver.openOutputStream methods. 

The returned AssetFileDescriptor can be a pipe or socket pair to enable
streaming of data.
If you are implementing this to return a full file, you should create the AssetFileDescriptor with AssetFileDescriptor.UNKNOWN_LENGTH to be compatible with applications that cannot handle sub-sections of files.
For use in Intents, you will want to implement getType to return the appropriate MIME type for the data returned here with the same URI. This will allow intent resolution to automatically determine the data MIME type and select the appropriate matching targets as part of its operation.
For better interoperability with other applications, it is recommended that for any URIs that can be opened, you also support queries on them containing at least the columns specified by OpenableColumns.
Params:
uri – The URI whose file is to be opened.
mode – Access mode for the file.  May be "r" for read-only access,
"w" for write-only access (erasing whatever data is currently in
the file), "wa" for write-only access to append to any existing data,
"rw" for read and write access on any existing data, and "rwt" for read
and write access that truncates any existing file.
signal – A signal to cancel the operation in progress, or null if none. For example, if you are downloading a file from the network to service a "rw" mode request, you should periodically call CancellationSignal.throwIfCanceled() to check whether the client has canceled the request and abort the download.
Throws:
FileNotFoundException – Throws FileNotFoundException if there is
no file associated with the given URI or the mode is invalid.
SecurityException – Throws SecurityException if the caller does
not have permission to access the file.
See Also:
openFile(Uri, String)
openFileHelper(Uri, String)
getType(Uri)
Returns:
Returns a new AssetFileDescriptor which you can use to access
the file./**
     * This is like {@link #openFile}, but can be implemented by providers
     * that need to be able to return sub-sections of files, often assets
     * inside of their .apk.
     * This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     *
     * <p>If you implement this, your clients must be able to deal with such
     * file slices, either directly with
     * {@link ContentResolver#openAssetFileDescriptor}, or by using the higher-level
     * {@link ContentResolver#openInputStream ContentResolver.openInputStream}
     * or {@link ContentResolver#openOutputStream ContentResolver.openOutputStream}
     * methods.
     * <p>
     * The returned AssetFileDescriptor can be a pipe or socket pair to enable
     * streaming of data.
     *
     * <p class="note">If you are implementing this to return a full file, you
     * should create the AssetFileDescriptor with
     * {@link AssetFileDescriptor#UNKNOWN_LENGTH} to be compatible with
     * applications that cannot handle sub-sections of files.</p>
     *
     * <p class="note">For use in Intents, you will want to implement {@link #getType}
     * to return the appropriate MIME type for the data returned here with
     * the same URI.  This will allow intent resolution to automatically determine the data MIME
     * type and select the appropriate matching targets as part of its operation.</p>
     *
     * <p class="note">For better interoperability with other applications, it is recommended
     * that for any URIs that can be opened, you also support queries on them
     * containing at least the columns specified by {@link android.provider.OpenableColumns}.</p>
     *
     * @param uri The URI whose file is to be opened.
     * @param mode Access mode for the file.  May be "r" for read-only access,
     * "w" for write-only access (erasing whatever data is currently in
     * the file), "wa" for write-only access to append to any existing data,
     * "rw" for read and write access on any existing data, and "rwt" for read
     * and write access that truncates any existing file.
     * @param signal A signal to cancel the operation in progress, or
     *            {@code null} if none. For example, if you are downloading a
     *            file from the network to service a "rw" mode request, you
     *            should periodically call
     *            {@link CancellationSignal#throwIfCanceled()} to check whether
     *            the client has canceled the request and abort the download.
     *
     * @return Returns a new AssetFileDescriptor which you can use to access
     * the file.
     *
     * @throws FileNotFoundException Throws FileNotFoundException if there is
     * no file associated with the given URI or the mode is invalid.
     * @throws SecurityException Throws SecurityException if the caller does
     * not have permission to access the file.
     *
     * @see #openFile(Uri, String)
     * @see #openFileHelper(Uri, String)
     * @see #getType(android.net.Uri)
     */
    public @Nullable AssetFileDescriptor openAssetFile(@NonNull Uri uri, @NonNull String mode,
            @Nullable CancellationSignal signal) throws FileNotFoundException {
        return openAssetFile(uri, mode);
    }

    
Convenience for subclasses that wish to implement openFile by looking up a column named "_data" at the given URI. 
Params:
uri – The URI to be opened.
mode – The file mode.  May be "r" for read-only access,
"w" for write-only access (erasing whatever data is currently in
the file), "wa" for write-only access to append to any existing data,
"rw" for read and write access on any existing data, and "rwt" for read
and write access that truncates any existing file.
Returns:
Returns a new ParcelFileDescriptor that can be used by the
client to access the file./**
     * Convenience for subclasses that wish to implement {@link #openFile}
     * by looking up a column named "_data" at the given URI.
     *
     * @param uri The URI to be opened.
     * @param mode The file mode.  May be "r" for read-only access,
     * "w" for write-only access (erasing whatever data is currently in
     * the file), "wa" for write-only access to append to any existing data,
     * "rw" for read and write access on any existing data, and "rwt" for read
     * and write access that truncates any existing file.
     *
     * @return Returns a new ParcelFileDescriptor that can be used by the
     * client to access the file.
     */
    protected final @NonNull ParcelFileDescriptor openFileHelper(@NonNull Uri uri,
            @NonNull String mode) throws FileNotFoundException {
        Cursor c = query(uri, new String[]{"_data"}, null, null, null);
        int count = (c != null) ? c.getCount() : 0;
        if (count != 1) {
            // If there is not exactly one result, throw an appropriate
            // exception.
            if (c != null) {
                c.close();
            }
            if (count == 0) {
                throw new FileNotFoundException("No entry for " + uri);
            }
            throw new FileNotFoundException("Multiple items at " + uri);
        }

        c.moveToFirst();
        int i = c.getColumnIndex("_data");
        String path = (i >= 0 ? c.getString(i) : null);
        c.close();
        if (path == null) {
            throw new FileNotFoundException("Column _data not found.");
        }

        int modeBits = ParcelFileDescriptor.parseMode(mode);
        return ParcelFileDescriptor.open(new File(path), modeBits);
    }

    
Called by a client to determine the types of data streams that this content provider supports for the given URI. The default implementation returns null, meaning no types. If your content provider stores data of a particular type, return that MIME type if it matches the given mimeTypeFilter. If it can perform type conversions, return an array of all supported MIME types that match mimeTypeFilter. 
Params:
uri – The data in the content provider being queried.
mimeTypeFilter – The type of data the client desires.  May be
a pattern, such as */* to retrieve all possible data types.
See Also:
getType(Uri)
openTypedAssetFile(Uri, String, Bundle)
ClipDescription.compareMimeTypes(String, String)
Returns:
Returns null if there are no possible data streams for the given mimeTypeFilter. Otherwise returns an array of all available concrete MIME types./**
     * Called by a client to determine the types of data streams that this
     * content provider supports for the given URI.  The default implementation
     * returns {@code null}, meaning no types.  If your content provider stores data
     * of a particular type, return that MIME type if it matches the given
     * mimeTypeFilter.  If it can perform type conversions, return an array
     * of all supported MIME types that match mimeTypeFilter.
     *
     * @param uri The data in the content provider being queried.
     * @param mimeTypeFilter The type of data the client desires.  May be
     * a pattern, such as *&#47;* to retrieve all possible data types.
     * @return Returns {@code null} if there are no possible data streams for the
     * given mimeTypeFilter.  Otherwise returns an array of all available
     * concrete MIME types.
     *
     * @see #getType(Uri)
     * @see #openTypedAssetFile(Uri, String, Bundle)
     * @see ClipDescription#compareMimeTypes(String, String)
     */
    public @Nullable String[] getStreamTypes(@NonNull Uri uri, @NonNull String mimeTypeFilter) {
        return null;
    }

    
Called by a client to open a read-only stream containing data of a particular MIME type. This is like openAssetFile(Uri, String), except the file can only be read-only and the content provider may perform data conversions to generate data of the desired type. 
The default implementation compares the given mimeType against the result of getType(Uri) and, if they match, simply calls openAssetFile(Uri, String). 
See ClipData for examples of the use and implementation of this method. 

The returned AssetFileDescriptor can be a pipe or socket pair to enable
streaming of data.
For better interoperability with other applications, it is recommended that for any URIs that can be opened, you also support queries on them containing at least the columns specified by OpenableColumns. You may also want to support other common columns if you have additional meta-data to supply, such as MediaColumns.DATE_ADDED in MediaColumns.
Params:
uri – The data in the content provider being queried.
mimeTypeFilter – The type of data the client desires.  May be
a pattern, such as */*, if the caller does not have specific type
requirements; in this case the content provider will pick its best
type matching the pattern.
opts – Additional options from the client.  The definitions of
these are specific to the content provider being called.
Throws:
FileNotFoundException – Throws FileNotFoundException if there is
no file associated with the given URI or the mode is invalid.
SecurityException – Throws SecurityException if the caller does
not have permission to access the data.
IllegalArgumentException – Throws IllegalArgumentException if the
content provider does not support the requested MIME type.
See Also:
getStreamTypes(Uri, String)
openAssetFile(Uri, String)
ClipDescription.compareMimeTypes(String, String)
Returns:
Returns a new AssetFileDescriptor from which the client can
read data of the desired type./**
     * Called by a client to open a read-only stream containing data of a
     * particular MIME type.  This is like {@link #openAssetFile(Uri, String)},
     * except the file can only be read-only and the content provider may
     * perform data conversions to generate data of the desired type.
     *
     * <p>The default implementation compares the given mimeType against the
     * result of {@link #getType(Uri)} and, if they match, simply calls
     * {@link #openAssetFile(Uri, String)}.
     *
     * <p>See {@link ClipData} for examples of the use and implementation
     * of this method.
     * <p>
     * The returned AssetFileDescriptor can be a pipe or socket pair to enable
     * streaming of data.
     *
     * <p class="note">For better interoperability with other applications, it is recommended
     * that for any URIs that can be opened, you also support queries on them
     * containing at least the columns specified by {@link android.provider.OpenableColumns}.
     * You may also want to support other common columns if you have additional meta-data
     * to supply, such as {@link android.provider.MediaStore.MediaColumns#DATE_ADDED}
     * in {@link android.provider.MediaStore.MediaColumns}.</p>
     *
     * @param uri The data in the content provider being queried.
     * @param mimeTypeFilter The type of data the client desires.  May be
     * a pattern, such as *&#47;*, if the caller does not have specific type
     * requirements; in this case the content provider will pick its best
     * type matching the pattern.
     * @param opts Additional options from the client.  The definitions of
     * these are specific to the content provider being called.
     *
     * @return Returns a new AssetFileDescriptor from which the client can
     * read data of the desired type.
     *
     * @throws FileNotFoundException Throws FileNotFoundException if there is
     * no file associated with the given URI or the mode is invalid.
     * @throws SecurityException Throws SecurityException if the caller does
     * not have permission to access the data.
     * @throws IllegalArgumentException Throws IllegalArgumentException if the
     * content provider does not support the requested MIME type.
     *
     * @see #getStreamTypes(Uri, String)
     * @see #openAssetFile(Uri, String)
     * @see ClipDescription#compareMimeTypes(String, String)
     */
    public @Nullable AssetFileDescriptor openTypedAssetFile(@NonNull Uri uri,
            @NonNull String mimeTypeFilter, @Nullable Bundle opts) throws FileNotFoundException {
        if ("*/*".equals(mimeTypeFilter)) {
            // If they can take anything, the untyped open call is good enough.
            return openAssetFile(uri, "r");
        }
        String baseType = getType(uri);
        if (baseType != null && ClipDescription.compareMimeTypes(baseType, mimeTypeFilter)) {
            // Use old untyped open call if this provider has a type for this
            // URI and it matches the request.
            return openAssetFile(uri, "r");
        }
        throw new FileNotFoundException("Can't open " + uri + " as type " + mimeTypeFilter);
    }


    
Called by a client to open a read-only stream containing data of a particular MIME type. This is like openAssetFile(Uri, String), except the file can only be read-only and the content provider may perform data conversions to generate data of the desired type. 
The default implementation compares the given mimeType against the result of getType(Uri) and, if they match, simply calls openAssetFile(Uri, String). 
See ClipData for examples of the use and implementation of this method. 

The returned AssetFileDescriptor can be a pipe or socket pair to enable
streaming of data.
For better interoperability with other applications, it is recommended that for any URIs that can be opened, you also support queries on them containing at least the columns specified by OpenableColumns. You may also want to support other common columns if you have additional meta-data to supply, such as MediaColumns.DATE_ADDED in MediaColumns.
Params:
uri – The data in the content provider being queried.
mimeTypeFilter – The type of data the client desires.  May be
a pattern, such as */*, if the caller does not have specific type
requirements; in this case the content provider will pick its best
type matching the pattern.
opts – Additional options from the client.  The definitions of
these are specific to the content provider being called.
signal – A signal to cancel the operation in progress, or null if none. For example, if you are downloading a file from the network to service a "rw" mode request, you should periodically call CancellationSignal.throwIfCanceled() to check whether the client has canceled the request and abort the download.
Throws:
FileNotFoundException – Throws FileNotFoundException if there is
no file associated with the given URI or the mode is invalid.
SecurityException – Throws SecurityException if the caller does
not have permission to access the data.
IllegalArgumentException – Throws IllegalArgumentException if the
content provider does not support the requested MIME type.
See Also:
getStreamTypes(Uri, String)
openAssetFile(Uri, String)
ClipDescription.compareMimeTypes(String, String)
Returns:
Returns a new AssetFileDescriptor from which the client can
read data of the desired type./**
     * Called by a client to open a read-only stream containing data of a
     * particular MIME type.  This is like {@link #openAssetFile(Uri, String)},
     * except the file can only be read-only and the content provider may
     * perform data conversions to generate data of the desired type.
     *
     * <p>The default implementation compares the given mimeType against the
     * result of {@link #getType(Uri)} and, if they match, simply calls
     * {@link #openAssetFile(Uri, String)}.
     *
     * <p>See {@link ClipData} for examples of the use and implementation
     * of this method.
     * <p>
     * The returned AssetFileDescriptor can be a pipe or socket pair to enable
     * streaming of data.
     *
     * <p class="note">For better interoperability with other applications, it is recommended
     * that for any URIs that can be opened, you also support queries on them
     * containing at least the columns specified by {@link android.provider.OpenableColumns}.
     * You may also want to support other common columns if you have additional meta-data
     * to supply, such as {@link android.provider.MediaStore.MediaColumns#DATE_ADDED}
     * in {@link android.provider.MediaStore.MediaColumns}.</p>
     *
     * @param uri The data in the content provider being queried.
     * @param mimeTypeFilter The type of data the client desires.  May be
     * a pattern, such as *&#47;*, if the caller does not have specific type
     * requirements; in this case the content provider will pick its best
     * type matching the pattern.
     * @param opts Additional options from the client.  The definitions of
     * these are specific to the content provider being called.
     * @param signal A signal to cancel the operation in progress, or
     *            {@code null} if none. For example, if you are downloading a
     *            file from the network to service a "rw" mode request, you
     *            should periodically call
     *            {@link CancellationSignal#throwIfCanceled()} to check whether
     *            the client has canceled the request and abort the download.
     *
     * @return Returns a new AssetFileDescriptor from which the client can
     * read data of the desired type.
     *
     * @throws FileNotFoundException Throws FileNotFoundException if there is
     * no file associated with the given URI or the mode is invalid.
     * @throws SecurityException Throws SecurityException if the caller does
     * not have permission to access the data.
     * @throws IllegalArgumentException Throws IllegalArgumentException if the
     * content provider does not support the requested MIME type.
     *
     * @see #getStreamTypes(Uri, String)
     * @see #openAssetFile(Uri, String)
     * @see ClipDescription#compareMimeTypes(String, String)
     */
    public @Nullable AssetFileDescriptor openTypedAssetFile(@NonNull Uri uri,
            @NonNull String mimeTypeFilter, @Nullable Bundle opts,
            @Nullable CancellationSignal signal) throws FileNotFoundException {
        return openTypedAssetFile(uri, mimeTypeFilter, opts);
    }

    
Interface to write a stream of data to a pipe. Use with ContentProvider.openPipeHelper. /**
     * Interface to write a stream of data to a pipe.  Use with
     * {@link ContentProvider#openPipeHelper}.
     */
    public interface PipeDataWriter<T> {
        
Called from a background thread to stream data out to a pipe.
Note that the pipe is blocking, so this thread can block on
writes for an arbitrary amount of time if the client is slow
at reading.
Params:
output – The pipe where data should be written.  This will be
closed for you upon returning from this function.
uri – The URI whose data is to be written.
mimeType – The desired type of data to be written.
opts – Options supplied by caller.
args – Your own custom arguments./**
         * Called from a background thread to stream data out to a pipe.
         * Note that the pipe is blocking, so this thread can block on
         * writes for an arbitrary amount of time if the client is slow
         * at reading.
         *
         * @param output The pipe where data should be written.  This will be
         * closed for you upon returning from this function.
         * @param uri The URI whose data is to be written.
         * @param mimeType The desired type of data to be written.
         * @param opts Options supplied by caller.
         * @param args Your own custom arguments.
         */
        public void writeDataToPipe(@NonNull ParcelFileDescriptor output, @NonNull Uri uri,
                @NonNull String mimeType, @Nullable Bundle opts, @Nullable T args);
    }

    
A helper function for implementing openTypedAssetFile, for creating a data pipe and background thread allowing you to stream generated data back to the client. This function returns a new ParcelFileDescriptor that should be returned to the caller (the caller is responsible for closing it). 
Params:
uri – The URI whose data is to be written.
mimeType – The desired type of data to be written.
opts – Options supplied by caller.
args – Your own custom arguments.
func – Interface implementing the function that will actually
stream the data.
Returns:
Returns a new ParcelFileDescriptor holding the read side of
the pipe.  This should be returned to the caller for reading; the caller
is responsible for closing it when done./**
     * A helper function for implementing {@link #openTypedAssetFile}, for
     * creating a data pipe and background thread allowing you to stream
     * generated data back to the client.  This function returns a new
     * ParcelFileDescriptor that should be returned to the caller (the caller
     * is responsible for closing it).
     *
     * @param uri The URI whose data is to be written.
     * @param mimeType The desired type of data to be written.
     * @param opts Options supplied by caller.
     * @param args Your own custom arguments.
     * @param func Interface implementing the function that will actually
     * stream the data.
     * @return Returns a new ParcelFileDescriptor holding the read side of
     * the pipe.  This should be returned to the caller for reading; the caller
     * is responsible for closing it when done.
     */
    public @NonNull <T> ParcelFileDescriptor openPipeHelper(final @NonNull Uri uri,
            final @NonNull String mimeType, final @Nullable Bundle opts, final @Nullable T args,
            final @NonNull PipeDataWriter<T> func) throws FileNotFoundException {
        try {
            final ParcelFileDescriptor[] fds = ParcelFileDescriptor.createPipe();

            AsyncTask<Object, Object, Object> task = new AsyncTask<Object, Object, Object>() {
                @Override
                protected Object doInBackground(Object... params) {
                    func.writeDataToPipe(fds[1], uri, mimeType, opts, args);
                    try {
                        fds[1].close();
                    } catch (IOException e) {
                        Log.w(TAG, "Failure closing pipe", e);
                    }
                    return null;
                }
            };
            task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, (Object[])null);

            return fds[0];
        } catch (IOException e) {
            throw new FileNotFoundException("failure making pipe");
        }
    }

    
Returns true if this instance is a temporary content provider.
Returns:
true if this instance is a temporary content provider/**
     * Returns true if this instance is a temporary content provider.
     * @return true if this instance is a temporary content provider
     */
    protected boolean isTemporary() {
        return false;
    }

    
Returns the Binder object for this provider.
Returns:
the Binder object for this provider
@hide
/**
     * Returns the Binder object for this provider.
     *
     * @return the Binder object for this provider
     * @hide
     */
    public IContentProvider getIContentProvider() {
        return mTransport;
    }

    
Like attachInfo(Context, ProviderInfo), but for use when directly instantiating the provider for testing. 
@hide
/**
     * Like {@link #attachInfo(Context, android.content.pm.ProviderInfo)}, but for use
     * when directly instantiating the provider for testing.
     * @hide
     */
    public void attachInfoForTesting(Context context, ProviderInfo info) {
        attachInfo(context, info, true);
    }

    
After being instantiated, this is called to tell the content provider
about itself.
Params:
context – The context this provider is running in
info – Registered information about this content provider/**
     * After being instantiated, this is called to tell the content provider
     * about itself.
     *
     * @param context The context this provider is running in
     * @param info Registered information about this content provider
     */
    public void attachInfo(Context context, ProviderInfo info) {
        attachInfo(context, info, false);
    }

    private void attachInfo(Context context, ProviderInfo info, boolean testing) {
        mNoPerms = testing;

        /*
         * Only allow it to be set once, so after the content service gives
         * this to us clients can't change it.
         */
        if (mContext == null) {
            mContext = context;
            if (context != null && mTransport != null) {
                mTransport.mAppOpsManager = (AppOpsManager) context.getSystemService(
                        Context.APP_OPS_SERVICE);
            }
            mMyUid = Process.myUid();
            if (info != null) {
                setReadPermission(info.readPermission);
                setWritePermission(info.writePermission);
                setPathPermissions(info.pathPermissions);
                mExported = info.exported;
                mSingleUser = (info.flags & ProviderInfo.FLAG_SINGLE_USER) != 0;
                setAuthorities(info.authority);
            }
            ContentProvider.this.onCreate();
        }
    }

    
Override this to handle requests to perform a batch of operations, or the default implementation will iterate over the operations and call ContentProviderOperation.apply on each of them. If all calls to ContentProviderOperation.apply succeed then a ContentProviderResult array with as many elements as there were operations will be returned. If any of the calls fail, it is up to the implementation how many of the others take effect. This method can be called from multiple threads, as described in Processes
and Threads.
Params:
operations – the operations to apply
Throws:
OperationApplicationException – thrown if any operation fails.
See Also:
ContentProviderOperation.apply
Returns:
the results of the applications/**
     * Override this to handle requests to perform a batch of operations, or the
     * default implementation will iterate over the operations and call
     * {@link ContentProviderOperation#apply} on each of them.
     * If all calls to {@link ContentProviderOperation#apply} succeed
     * then a {@link ContentProviderResult} array with as many
     * elements as there were operations will be returned.  If any of the calls
     * fail, it is up to the implementation how many of the others take effect.
     * This method can be called from multiple threads, as described in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
     * and Threads</a>.
     *
     * @param operations the operations to apply
     * @return the results of the applications
     * @throws OperationApplicationException thrown if any operation fails.
     * @see ContentProviderOperation#apply
     */
    public @NonNull ContentProviderResult[] applyBatch(
            @NonNull ArrayList<ContentProviderOperation> operations)
                    throws OperationApplicationException {
        final int numOperations = operations.size();
        final ContentProviderResult[] results = new ContentProviderResult[numOperations];
        for (int i = 0; i < numOperations; i++) {
            results[i] = operations.get(i).apply(this, results, i);
        }
        return results;
    }

    
Call a provider-defined method.  This can be used to implement
interfaces that are cheaper and/or unnatural for a table-like
model.
WARNING: The framework does no permission checking
on this entry into the content provider besides the basic ability for the application
to get access to the provider at all.  For example, it has no idea whether the call
being executed may read or write data in the provider, so can't enforce those
individual permissions.  Any implementation of this method must
do its own permission checks on incoming calls to make sure they are allowed.
Params:
method – method name to call. Opaque to framework, but should not be null.
arg – provider-defined String argument. May be null.
extras – provider-defined Bundle argument. May be null.
Returns:
provider-defined return value. May be null, which is also the default for providers which don't implement any call methods./**
     * Call a provider-defined method.  This can be used to implement
     * interfaces that are cheaper and/or unnatural for a table-like
     * model.
     *
     * <p class="note"><strong>WARNING:</strong> The framework does no permission checking
     * on this entry into the content provider besides the basic ability for the application
     * to get access to the provider at all.  For example, it has no idea whether the call
     * being executed may read or write data in the provider, so can't enforce those
     * individual permissions.  Any implementation of this method <strong>must</strong>
     * do its own permission checks on incoming calls to make sure they are allowed.</p>
     *
     * @param method method name to call.  Opaque to framework, but should not be {@code null}.
     * @param arg provider-defined String argument.  May be {@code null}.
     * @param extras provider-defined Bundle argument.  May be {@code null}.
     * @return provider-defined return value.  May be {@code null}, which is also
     *   the default for providers which don't implement any call methods.
     */
    public @Nullable Bundle call(@NonNull String method, @Nullable String arg,
            @Nullable Bundle extras) {
        return null;
    }

    
Implement this to shut down the ContentProvider instance. You can then
invoke this method in unit tests.

Android normally handles ContentProvider startup and shutdown
automatically. You do not need to start up or shut down a
ContentProvider. When you invoke a test method on a ContentProvider,
however, a ContentProvider instance is started and keeps running after
the test finishes, even if a succeeding test instantiates another
ContentProvider. A conflict develops because the two instances are
usually running against the same underlying data source (for example, an
sqlite database).


Implementing shutDown() avoids this conflict by providing a way to
terminate the ContentProvider. This method can also prevent memory leaks
from multiple instantiations of the ContentProvider, and it can ensure
unit test isolation by allowing you to completely clean up the test
fixture before moving on to the next test.

/**
     * Implement this to shut down the ContentProvider instance. You can then
     * invoke this method in unit tests.
     *
     * <p>
     * Android normally handles ContentProvider startup and shutdown
     * automatically. You do not need to start up or shut down a
     * ContentProvider. When you invoke a test method on a ContentProvider,
     * however, a ContentProvider instance is started and keeps running after
     * the test finishes, even if a succeeding test instantiates another
     * ContentProvider. A conflict develops because the two instances are
     * usually running against the same underlying data source (for example, an
     * sqlite database).
     * </p>
     * <p>
     * Implementing shutDown() avoids this conflict by providing a way to
     * terminate the ContentProvider. This method can also prevent memory leaks
     * from multiple instantiations of the ContentProvider, and it can ensure
     * unit test isolation by allowing you to completely clean up the test
     * fixture before moving on to the next test.
     * </p>
     */
    public void shutdown() {
        Log.w(TAG, "implement ContentProvider shutdown() to make sure all database " +
                "connections are gracefully shutdown");
    }

    
Print the Provider's state into the given stream.  This gets invoked if
you run "adb shell dumpsys activity provider <provider_component_name>".
Params:
fd – The raw file descriptor that the dump is being sent to.
writer – The PrintWriter to which you should dump your state.  This will be
closed for you after you return.
args – additional arguments to the dump request./**
     * Print the Provider's state into the given stream.  This gets invoked if
     * you run "adb shell dumpsys activity provider &lt;provider_component_name&gt;".
     *
     * @param fd The raw file descriptor that the dump is being sent to.
     * @param writer The PrintWriter to which you should dump your state.  This will be
     * closed for you after you return.
     * @param args additional arguments to the dump request.
     */
    public void dump(FileDescriptor fd, PrintWriter writer, String[] args) {
        writer.println("nothing to dump");
    }

    
@hide
/** @hide */
    public Uri validateIncomingUri(Uri uri) throws SecurityException {
        String auth = uri.getAuthority();
        if (!mSingleUser) {
            int userId = getUserIdFromAuthority(auth, UserHandle.USER_CURRENT);
            if (userId != UserHandle.USER_CURRENT && userId != mContext.getUserId()) {
                throw new SecurityException("trying to query a ContentProvider in user "
                        + mContext.getUserId() + " with a uri belonging to user " + userId);
            }
        }
        if (!matchesOurAuthorities(getAuthorityWithoutUserId(auth))) {
            String message = "The authority of the uri " + uri + " does not match the one of the "
                    + "contentProvider: ";
            if (mAuthority != null) {
                message += mAuthority;
            } else {
                message += Arrays.toString(mAuthorities);
            }
            throw new SecurityException(message);
        }

        // Normalize the path by removing any empty path segments, which can be
        // a source of security issues.
        final String encodedPath = uri.getEncodedPath();
        if (encodedPath != null && encodedPath.indexOf("//") != -1) {
            final Uri normalized = uri.buildUpon()
                    .encodedPath(encodedPath.replaceAll("//+", "/")).build();
            Log.w(TAG, "Normalized " + uri + " to " + normalized
                    + " to avoid possible security issues");
            return normalized;
        } else {
            return uri;
        }
    }

    
@hide
/** @hide */
    private Uri maybeGetUriWithoutUserId(Uri uri) {
        if (mSingleUser) {
            return uri;
        }
        return getUriWithoutUserId(uri);
    }

    
@hide
/** @hide */
    public static int getUserIdFromAuthority(String auth, int defaultUserId) {
        if (auth == null) return defaultUserId;
        int end = auth.lastIndexOf('@');
        if (end == -1) return defaultUserId;
        String userIdString = auth.substring(0, end);
        try {
            return Integer.parseInt(userIdString);
        } catch (NumberFormatException e) {
            Log.w(TAG, "Error parsing userId.", e);
            return UserHandle.USER_NULL;
        }
    }

    
@hide
/** @hide */
    public static int getUserIdFromAuthority(String auth) {
        return getUserIdFromAuthority(auth, UserHandle.USER_CURRENT);
    }

    
@hide
/** @hide */
    public static int getUserIdFromUri(Uri uri, int defaultUserId) {
        if (uri == null) return defaultUserId;
        return getUserIdFromAuthority(uri.getAuthority(), defaultUserId);
    }

    
@hide
/** @hide */
    public static int getUserIdFromUri(Uri uri) {
        return getUserIdFromUri(uri, UserHandle.USER_CURRENT);
    }

    
Removes userId part from authority string. Expects format:
userId@some.authority
If there is no userId in the authority, it symply returns the argument
@hide
/**
     * Removes userId part from authority string. Expects format:
     * userId@some.authority
     * If there is no userId in the authority, it symply returns the argument
     * @hide
     */
    public static String getAuthorityWithoutUserId(String auth) {
        if (auth == null) return null;
        int end = auth.lastIndexOf('@');
        return auth.substring(end+1);
    }

    
@hide
/** @hide */
    public static Uri getUriWithoutUserId(Uri uri) {
        if (uri == null) return null;
        Uri.Builder builder = uri.buildUpon();
        builder.authority(getAuthorityWithoutUserId(uri.getAuthority()));
        return builder.build();
    }

    
@hide
/** @hide */
    public static boolean uriHasUserId(Uri uri) {
        if (uri == null) return false;
        return !TextUtils.isEmpty(uri.getUserInfo());
    }

    
@hide
/** @hide */
    public static Uri maybeAddUserId(Uri uri, int userId) {
        if (uri == null) return null;
        if (userId != UserHandle.USER_CURRENT
                && ContentResolver.SCHEME_CONTENT.equals(uri.getScheme())) {
            if (!uriHasUserId(uri)) {
                //We don't add the user Id if there's already one
                Uri.Builder builder = uri.buildUpon();
                builder.encodedAuthority("" + userId + "@" + uri.getEncodedAuthority());
                return builder.build();
            }
        }
        return uri;
    }
}