/*
 * Copyright (C) 2007 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.database;

import android.net.Uri;
import android.os.Handler;
import android.os.UserHandle;

Receives call backs for changes to content. Must be implemented by objects which are added to a ContentObservable. /**
 * Receives call backs for changes to content.
 * Must be implemented by objects which are added to a {@link ContentObservable}.
 */
public abstract class ContentObserver {
    private final Object mLock = new Object();
    private Transport mTransport; // guarded by mLock

    Handler mHandler;

    
Creates a content observer.
Params:
handler – The handler to run onChange on, or null if none./**
     * Creates a content observer.
     *
     * @param handler The handler to run {@link #onChange} on, or null if none.
     */
    public ContentObserver(Handler handler) {
        mHandler = handler;
    }

    
Gets access to the binder transport object. Not for public consumption.
{@hide}
/**
     * Gets access to the binder transport object. Not for public consumption.
     *
     * {@hide}
     */
    public IContentObserver getContentObserver() {
        synchronized (mLock) {
            if (mTransport == null) {
                mTransport = new Transport(this);
            }
            return mTransport;
        }
    }

    
Gets access to the binder transport object, and unlinks the transport object
from the ContentObserver. Not for public consumption.
{@hide}
/**
     * Gets access to the binder transport object, and unlinks the transport object
     * from the ContentObserver. Not for public consumption.
     *
     * {@hide}
     */
    public IContentObserver releaseContentObserver() {
        synchronized (mLock) {
            final Transport oldTransport = mTransport;
            if (oldTransport != null) {
                oldTransport.releaseContentObserver();
                mTransport = null;
            }
            return oldTransport;
        }
    }

    
Returns true if this observer is interested receiving self-change notifications.
Subclasses should override this method to indicate whether the observer
is interested in receiving notifications for changes that it made to the
content itself.
Returns:
True if self-change notifications should be delivered to the observer./**
     * Returns true if this observer is interested receiving self-change notifications.
     *
     * Subclasses should override this method to indicate whether the observer
     * is interested in receiving notifications for changes that it made to the
     * content itself.
     *
     * @return True if self-change notifications should be delivered to the observer.
     */
    public boolean deliverSelfNotifications() {
        return false;
    }

    
This method is called when a content change occurs.

Subclasses should override this method to handle content changes.

Params:
selfChange – True if this is a self-change notification./**
     * This method is called when a content change occurs.
     * <p>
     * Subclasses should override this method to handle content changes.
     * </p>
     *
     * @param selfChange True if this is a self-change notification.
     */
    public void onChange(boolean selfChange) {
        // Do nothing.  Subclass should override.
    }

    
This method is called when a content change occurs.
Includes the changed content Uri when available.
 Subclasses should override this method to handle content changes. To ensure correct operation on older versions of the framework that did not provide a Uri argument, applications should also implement the onChange(boolean) overload of this method whenever they implement the onChange(boolean, Uri) overload. 

Example implementation:
 // Implement the onChange(boolean) method to delegate the change notification to // the onChange(boolean, Uri) method to ensure correct operation on older versions // of the framework that did not have the onChange(boolean, Uri) method. @Override public void onChange(boolean selfChange) { onChange(selfChange, null); } // Implement the onChange(boolean, Uri) method to take advantage of the new Uri argument. @Override public void onChange(boolean selfChange, Uri uri) { // Handle change. } 

Params:
selfChange – True if this is a self-change notification.
uri – The Uri of the changed content, or null if unknown./**
     * This method is called when a content change occurs.
     * Includes the changed content Uri when available.
     * <p>
     * Subclasses should override this method to handle content changes.
     * To ensure correct operation on older versions of the framework that
     * did not provide a Uri argument, applications should also implement
     * the {@link #onChange(boolean)} overload of this method whenever they
     * implement the {@link #onChange(boolean, Uri)} overload.
     * </p><p>
     * Example implementation:
     * <pre><code>
     * // Implement the onChange(boolean) method to delegate the change notification to
     * // the onChange(boolean, Uri) method to ensure correct operation on older versions
     * // of the framework that did not have the onChange(boolean, Uri) method.
     * {@literal @Override}
     * public void onChange(boolean selfChange) {
     *     onChange(selfChange, null);
     * }
     *
     * // Implement the onChange(boolean, Uri) method to take advantage of the new Uri argument.
     * {@literal @Override}
     * public void onChange(boolean selfChange, Uri uri) {
     *     // Handle change.
     * }
     * </code></pre>
     * </p>
     *
     * @param selfChange True if this is a self-change notification.
     * @param uri The Uri of the changed content, or null if unknown.
     */
    public void onChange(boolean selfChange, Uri uri) {
        onChange(selfChange);
    }

    
Dispatches a change notification to the observer. Includes the changed
content Uri when available and also the user whose content changed.
Params:
selfChange – True if this is a self-change notification.
uri – The Uri of the changed content, or null if unknown.
userId – The user whose content changed. Can be either a specific user or UserHandle.USER_ALL.
@hide
/**
     * Dispatches a change notification to the observer. Includes the changed
     * content Uri when available and also the user whose content changed.
     *
     * @param selfChange True if this is a self-change notification.
     * @param uri The Uri of the changed content, or null if unknown.
     * @param userId The user whose content changed. Can be either a specific
     *         user or {@link UserHandle#USER_ALL}.
     *
     * @hide
     */
    public void onChange(boolean selfChange, Uri uri, int userId) {
        onChange(selfChange, uri);
    }

    
Dispatches a change notification to the observer.
 If a Handler was supplied to the ContentObserver constructor, then a call to the onChange method is posted to the handler's message queue. Otherwise, the onChange method is invoked immediately on this thread. 
Params:
selfChange – True if this is a self-change notification.
Deprecated:
Use dispatchChange(boolean, Uri) instead./**
     * Dispatches a change notification to the observer.
     * <p>
     * If a {@link Handler} was supplied to the {@link ContentObserver} constructor,
     * then a call to the {@link #onChange} method is posted to the handler's message queue.
     * Otherwise, the {@link #onChange} method is invoked immediately on this thread.
     * </p>
     *
     * @param selfChange True if this is a self-change notification.
     *
     * @deprecated Use {@link #dispatchChange(boolean, Uri)} instead.
     */
    @Deprecated
    public final void dispatchChange(boolean selfChange) {
        dispatchChange(selfChange, null);
    }

    
Dispatches a change notification to the observer.
Includes the changed content Uri when available.
 If a Handler was supplied to the ContentObserver constructor, then a call to the onChange method is posted to the handler's message queue. Otherwise, the onChange method is invoked immediately on this thread. 
Params:
selfChange – True if this is a self-change notification.
uri – The Uri of the changed content, or null if unknown./**
     * Dispatches a change notification to the observer.
     * Includes the changed content Uri when available.
     * <p>
     * If a {@link Handler} was supplied to the {@link ContentObserver} constructor,
     * then a call to the {@link #onChange} method is posted to the handler's message queue.
     * Otherwise, the {@link #onChange} method is invoked immediately on this thread.
     * </p>
     *
     * @param selfChange True if this is a self-change notification.
     * @param uri The Uri of the changed content, or null if unknown.
     */
    public final void dispatchChange(boolean selfChange, Uri uri) {
        dispatchChange(selfChange, uri, UserHandle.getCallingUserId());
    }

    
Dispatches a change notification to the observer. Includes the changed
content Uri when available and also the user whose content changed.
 If a Handler was supplied to the ContentObserver constructor, then a call to the onChange method is posted to the handler's message queue. Otherwise, the onChange method is invoked immediately on this thread. 
Params:
selfChange – True if this is a self-change notification.
uri – The Uri of the changed content, or null if unknown.
userId – The user whose content changed./**
     * Dispatches a change notification to the observer. Includes the changed
     * content Uri when available and also the user whose content changed.
     * <p>
     * If a {@link Handler} was supplied to the {@link ContentObserver} constructor,
     * then a call to the {@link #onChange} method is posted to the handler's message queue.
     * Otherwise, the {@link #onChange} method is invoked immediately on this thread.
     * </p>
     *
     * @param selfChange True if this is a self-change notification.
     * @param uri The Uri of the changed content, or null if unknown.
     * @param userId The user whose content changed.
     */
    private void dispatchChange(boolean selfChange, Uri uri, int userId) {
        if (mHandler == null) {
            onChange(selfChange, uri, userId);
        } else {
            mHandler.post(new NotificationRunnable(selfChange, uri, userId));
        }
    }


    private final class NotificationRunnable implements Runnable {
        private final boolean mSelfChange;
        private final Uri mUri;
        private final int mUserId;

        public NotificationRunnable(boolean selfChange, Uri uri, int userId) {
            mSelfChange = selfChange;
            mUri = uri;
            mUserId = userId;
        }

        @Override
        public void run() {
            ContentObserver.this.onChange(mSelfChange, mUri, mUserId);
        }
    }

    private static final class Transport extends IContentObserver.Stub {
        private ContentObserver mContentObserver;

        public Transport(ContentObserver contentObserver) {
            mContentObserver = contentObserver;
        }

        @Override
        public void onChange(boolean selfChange, Uri uri, int userId) {
            ContentObserver contentObserver = mContentObserver;
            if (contentObserver != null) {
                contentObserver.dispatchChange(selfChange, uri, userId);
            }
        }

        public void releaseContentObserver() {
            mContentObserver = null;
        }
    }
}