https://source.android.com/ 
/*
 * Copyright (C) 2011 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.widget;

import android.app.ActivityManager;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.database.DataSetObservable;
import android.os.AsyncTask;
import android.text.TextUtils;
import android.util.Log;
import android.util.Xml;

import com.android.internal.content.PackageMonitor;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlSerializer;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.math.BigDecimal;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


 This class represents a data model for choosing a component for handing a given Intent. The model is responsible for querying the system for activities that can handle the given intent and order found activities based on historical data of previous choices. The historical data is stored in an application private file. If a client does not want to have persistent choice history the file can be omitted, thus the activities will be ordered based on historical usage for the current session. 



For each backing history file there is a singleton instance of this class. Thus,
several clients that specify the same history file will share the same model. Note
that if multiple clients are sharing the same model they should implement semantically
equivalent functionality since setting the model intent will change the found
activities and they may be inconsistent with the functionality of some of the clients.
For example, choosing a share activity can be implemented by a single backing
model and two different views for performing the selection. If however, one of the
views is used for sharing but the other for importing, for example, then each
view should be backed by a separate model.




The way clients interact with this class is as follows:






 // Get a model and set it to a couple of clients with semantically similar function.
 ActivityChooserModel dataModel =
     ActivityChooserModel.get(context, "task_specific_history_file_name.xml");
 ActivityChooserModelClient modelClient1 = getActivityChooserModelClient1();
 modelClient1.setActivityChooserModel(dataModel);
 ActivityChooserModelClient modelClient2 = getActivityChooserModelClient2();
 modelClient2.setActivityChooserModel(dataModel);
 // Set an intent to choose a an activity for.
 dataModel.setIntent(intent);






Note: This class is thread safe.



@hide
/**
 * <p>
 * This class represents a data model for choosing a component for handing a
 * given {@link Intent}. The model is responsible for querying the system for
 * activities that can handle the given intent and order found activities
 * based on historical data of previous choices. The historical data is stored
 * in an application private file. If a client does not want to have persistent
 * choice history the file can be omitted, thus the activities will be ordered
 * based on historical usage for the current session.
 * <p>
 * </p>
 * For each backing history file there is a singleton instance of this class. Thus,
 * several clients that specify the same history file will share the same model. Note
 * that if multiple clients are sharing the same model they should implement semantically
 * equivalent functionality since setting the model intent will change the found
 * activities and they may be inconsistent with the functionality of some of the clients.
 * For example, choosing a share activity can be implemented by a single backing
 * model and two different views for performing the selection. If however, one of the
 * views is used for sharing but the other for importing, for example, then each
 * view should be backed by a separate model.
 * </p>
 * <p>
 * The way clients interact with this class is as follows:
 * </p>
 * <p>
 * <pre>
 * <code>
 *  // Get a model and set it to a couple of clients with semantically similar function.
 *  ActivityChooserModel dataModel =
 *      ActivityChooserModel.get(context, "task_specific_history_file_name.xml");
 *
 *  ActivityChooserModelClient modelClient1 = getActivityChooserModelClient1();
 *  modelClient1.setActivityChooserModel(dataModel);
 *
 *  ActivityChooserModelClient modelClient2 = getActivityChooserModelClient2();
 *  modelClient2.setActivityChooserModel(dataModel);
 *
 *  // Set an intent to choose a an activity for.
 *  dataModel.setIntent(intent);
 * <pre>
 * <code>
 * </p>
 * <p>
 * <strong>Note:</strong> This class is thread safe.
 * </p>
 *
 * @hide
 */
public class ActivityChooserModel extends DataSetObservable {

    
Client that utilizes an ActivityChooserModel. 
/**
     * Client that utilizes an {@link ActivityChooserModel}.
     */
    public interface ActivityChooserModelClient {

        
Params:
  • dataModel – The model.
/**
         * Sets the {@link ActivityChooserModel}.
         *
         * @param dataModel The model.
         */
        public void setActivityChooserModel(ActivityChooserModel dataModel);
    }

    
Defines a sorter that is responsible for sorting the activities
based on the provided historical choices and an intent.

/**
     * Defines a sorter that is responsible for sorting the activities
     * based on the provided historical choices and an intent.
     */
    public interface ActivitySorter {

        
Sorts the activities in descending order of relevance
based on previous history and an intent.

Params:
  • intent – The Intent.
  • activities – Activities to be sorted.
  • historicalRecords – Historical records.
/**
         * Sorts the <code>activities</code> in descending order of relevance
         * based on previous history and an intent.
         *
         * @param intent The {@link Intent}.
         * @param activities Activities to be sorted.
         * @param historicalRecords Historical records.
         */
        // This cannot be done by a simple comparator since an Activity weight
        // is computed from history. Note that Activity implements Comparable.
        public void sort(Intent intent, List<ActivityResolveInfo> activities,
                List<HistoricalRecord> historicalRecords);
    }

    
Listener for choosing an activity.

/**
     * Listener for choosing an activity.
     */
    public interface OnChooseActivityListener {

        
Called when an activity has been chosen. The client can decide whether an activity can be chosen and if so the caller of ActivityChooserModel.chooseActivity(int) will receive and Intent for launching it. 

Note: Modifying the intent is not permitted and
    any changes to the latter will be ignored.



Params:
  • host – The listener's host model.
  • intent – The intent for launching the chosen activity.
See Also:
Returns:Whether the intent is handled and should not be delivered to clients.
/**
         * Called when an activity has been chosen. The client can decide whether
         * an activity can be chosen and if so the caller of
         * {@link ActivityChooserModel#chooseActivity(int)} will receive and {@link Intent}
         * for launching it.
         * <p>
         * <strong>Note:</strong> Modifying the intent is not permitted and
         *     any changes to the latter will be ignored.
         * </p>
         *
         * @param host The listener's host model.
         * @param intent The intent for launching the chosen activity.
         * @return Whether the intent is handled and should not be delivered to clients.
         *
         * @see ActivityChooserModel#chooseActivity(int)
         */
        public boolean onChooseActivity(ActivityChooserModel host, Intent intent);
    }

    
Flag for selecting debug mode.

/**
     * Flag for selecting debug mode.
     */
    private static final boolean DEBUG = false;

    
Tag used for logging.

/**
     * Tag used for logging.
     */
    private static final String LOG_TAG = ActivityChooserModel.class.getSimpleName();

    
The root tag in the history file.

/**
     * The root tag in the history file.
     */
    private static final String TAG_HISTORICAL_RECORDS = "historical-records";

    
The tag for a record in the history file.

/**
     * The tag for a record in the history file.
     */
    private static final String TAG_HISTORICAL_RECORD = "historical-record";

    
Attribute for the activity.

/**
     * Attribute for the activity.
     */
    private static final String ATTRIBUTE_ACTIVITY = "activity";

    
Attribute for the choice time.

/**
     * Attribute for the choice time.
     */
    private static final String ATTRIBUTE_TIME = "time";

    
Attribute for the choice weight.

/**
     * Attribute for the choice weight.
     */
    private static final String ATTRIBUTE_WEIGHT = "weight";

    
The default name of the choice history file.

/**
     * The default name of the choice history file.
     */
    public static final String DEFAULT_HISTORY_FILE_NAME =
        "activity_choser_model_history.xml";

    
The default maximal length of the choice history.

/**
     * The default maximal length of the choice history.
     */
    public static final int DEFAULT_HISTORY_MAX_LENGTH = 50;

    
The amount with which to inflate a chosen activity when set as default.

/**
     * The amount with which to inflate a chosen activity when set as default.
     */
    private static final int DEFAULT_ACTIVITY_INFLATION = 5;

    
Default weight for a choice record.

/**
     * Default weight for a choice record.
     */
    private static final float DEFAULT_HISTORICAL_RECORD_WEIGHT = 1.0f;

    
The extension of the history file.

/**
     * The extension of the history file.
     */
    private static final String HISTORY_FILE_EXTENSION = ".xml";

    
An invalid item index.

/**
     * An invalid item index.
     */
    private static final int INVALID_INDEX = -1;

    
Lock to guard the model registry.

/**
     * Lock to guard the model registry.
     */
    private static final Object sRegistryLock = new Object();

    
This the registry for data models.

/**
     * This the registry for data models.
     */
    private static final Map<String, ActivityChooserModel> sDataModelRegistry =
        new HashMap<String, ActivityChooserModel>();

    
Lock for synchronizing on this instance.

/**
     * Lock for synchronizing on this instance.
     */
    private final Object mInstanceLock = new Object();

    
List of activities that can handle the current intent.

/**
     * List of activities that can handle the current intent.
     */
    private final List<ActivityResolveInfo> mActivities = new ArrayList<ActivityResolveInfo>();

    
List with historical choice records.

/**
     * List with historical choice records.
     */
    private final List<HistoricalRecord> mHistoricalRecords = new ArrayList<HistoricalRecord>();

    
Monitor for added and removed packages.

/**
     * Monitor for added and removed packages.
     */
    private final PackageMonitor mPackageMonitor = new DataModelPackageMonitor();

    
Context for accessing resources.

/**
     * Context for accessing resources.
     */
    private final Context mContext;

    
The name of the history file that backs this model.

/**
     * The name of the history file that backs this model.
     */
    private final String mHistoryFileName;

    
The intent for which a activity is being chosen.

/**
     * The intent for which a activity is being chosen.
     */
    private Intent mIntent;

    
The sorter for ordering activities based on intent and past choices.

/**
     * The sorter for ordering activities based on intent and past choices.
     */
    private ActivitySorter mActivitySorter = new DefaultSorter();

    
The maximal length of the choice history.

/**
     * The maximal length of the choice history.
     */
    private int mHistoryMaxSize = DEFAULT_HISTORY_MAX_LENGTH;

    
Flag whether choice history can be read. In general many clients can share the same data model and readHistoricalDataIfNeeded() may be called by arbitrary of them any number of times. Therefore, this class guarantees that the very first read succeeds and subsequent reads can be performed only after a call to persistHistoricalDataIfNeeded() followed by change of the share records. 
/**
     * Flag whether choice history can be read. In general many clients can
     * share the same data model and {@link #readHistoricalDataIfNeeded()} may be called
     * by arbitrary of them any number of times. Therefore, this class guarantees
     * that the very first read succeeds and subsequent reads can be performed
     * only after a call to {@link #persistHistoricalDataIfNeeded()} followed by change
     * of the share records.
     */
    private boolean mCanReadHistoricalData = true;

    
Flag whether the choice history was read. This is used to enforce that before calling persistHistoricalDataIfNeeded() a call to persistHistoricalDataIfNeeded() has been made. This aims to avoid a scenario in which a choice history file exits, it is not read yet and it is overwritten. Note that always all historical records are read in full and the file is rewritten. This is necessary since we need to purge old records that are outside of the sliding window of past choices. 
/**
     * Flag whether the choice history was read. This is used to enforce that
     * before calling {@link #persistHistoricalDataIfNeeded()} a call to
     * {@link #persistHistoricalDataIfNeeded()} has been made. This aims to avoid a
     * scenario in which a choice history file exits, it is not read yet and
     * it is overwritten. Note that always all historical records are read in
     * full and the file is rewritten. This is necessary since we need to
     * purge old records that are outside of the sliding window of past choices.
     */
    private boolean mReadShareHistoryCalled = false;

    
Flag whether the choice records have changed. In general many clients can share the same data model and persistHistoricalDataIfNeeded() may be called by arbitrary of them any number of times. Therefore, this class guarantees that choice history will be persisted only if it has changed. 
/**
     * Flag whether the choice records have changed. In general many clients can
     * share the same data model and {@link #persistHistoricalDataIfNeeded()} may be called
     * by arbitrary of them any number of times. Therefore, this class guarantees
     * that choice history will be persisted only if it has changed.
     */
    private boolean mHistoricalRecordsChanged = true;

    
Flag whether to reload the activities for the current intent.

/**
     * Flag whether to reload the activities for the current intent.
     */
    private boolean mReloadActivities = false;

    
Policy for controlling how the model handles chosen activities.

/**
     * Policy for controlling how the model handles chosen activities.
     */
    private OnChooseActivityListener mActivityChoserModelPolicy;

    
Gets the data model backed by the contents of the provided file with historical data.
Note that only one data model is backed by a given file, thus multiple calls with
the same file name will return the same model instance. If no such instance is present
it is created.


Note: To use the default historical data file clients should explicitly pass as file name DEFAULT_HISTORY_FILE_NAME. If no persistence of the choice history is desired clients should pass null for the file name. In such
case a new model is returned for each invocation.




Always use difference historical data files for semantically different actions.
For example, sharing is different from importing.



Params:
  • context – Context for loading resources.
  • historyFileName – File name with choice history, null
       if the model should not be backed by a file. In this case the activities
       will be ordered only by data from the current session.
Returns:The model.
/**
     * Gets the data model backed by the contents of the provided file with historical data.
     * Note that only one data model is backed by a given file, thus multiple calls with
     * the same file name will return the same model instance. If no such instance is present
     * it is created.
     * <p>
     * <strong>Note:</strong> To use the default historical data file clients should explicitly
     * pass as file name {@link #DEFAULT_HISTORY_FILE_NAME}. If no persistence of the choice
     * history is desired clients should pass <code>null</code> for the file name. In such
     * case a new model is returned for each invocation.
     * </p>
     *
     * <p>
     * <strong>Always use difference historical data files for semantically different actions.
     * For example, sharing is different from importing.</strong>
     * </p>
     *
     * @param context Context for loading resources.
     * @param historyFileName File name with choice history, <code>null</code>
     *        if the model should not be backed by a file. In this case the activities
     *        will be ordered only by data from the current session.
     *
     * @return The model.
     */
    public static ActivityChooserModel get(Context context, String historyFileName) {
        synchronized (sRegistryLock) {
            ActivityChooserModel dataModel = sDataModelRegistry.get(historyFileName);
            if (dataModel == null) {
                dataModel = new ActivityChooserModel(context, historyFileName);
                sDataModelRegistry.put(historyFileName, dataModel);
            }
            return dataModel;
        }
    }

    
Creates a new instance.

Params:
  • context – Context for loading resources.
  • historyFileName – The history XML file.
/**
     * Creates a new instance.
     *
     * @param context Context for loading resources.
     * @param historyFileName The history XML file.
     */
    private ActivityChooserModel(Context context, String historyFileName) {
        mContext = context.getApplicationContext();
        if (!TextUtils.isEmpty(historyFileName)
                && !historyFileName.endsWith(HISTORY_FILE_EXTENSION)) {
            mHistoryFileName = historyFileName + HISTORY_FILE_EXTENSION;
        } else {
            mHistoryFileName = historyFileName;
        }
        mPackageMonitor.register(mContext, null, true);
    }

    
Sets an intent for which to choose a activity.


Note: Clients must set only semantically similar
intents for each data model.



Params:
  • intent – The intent.
/**
     * Sets an intent for which to choose a activity.
     * <p>
     * <strong>Note:</strong> Clients must set only semantically similar
     * intents for each data model.
     * <p>
     *
     * @param intent The intent.
     */
    public void setIntent(Intent intent) {
        synchronized (mInstanceLock) {
            if (mIntent == intent) {
                return;
            }
            mIntent = intent;
            mReloadActivities = true;
            ensureConsistentState();
        }
    }

    
Gets the intent for which a activity is being chosen.

Returns:The intent.
/**
     * Gets the intent for which a activity is being chosen.
     *
     * @return The intent.
     */
    public Intent getIntent() {
        synchronized (mInstanceLock) {
            return mIntent;
        }
    }

    
Gets the number of activities that can handle the intent.

See Also:
Returns:The activity count.
/**
     * Gets the number of activities that can handle the intent.
     *
     * @return The activity count.
     *
     * @see #setIntent(Intent)
     */
    public int getActivityCount() {
        synchronized (mInstanceLock) {
            ensureConsistentState();
            return mActivities.size();
        }
    }

    
Gets an activity at a given index.

See Also:
Returns:The activity.
/**
     * Gets an activity at a given index.
     *
     * @return The activity.
     *
     * @see ActivityResolveInfo
     * @see #setIntent(Intent)
     */
    public ResolveInfo getActivity(int index) {
        synchronized (mInstanceLock) {
            ensureConsistentState();
            return mActivities.get(index).resolveInfo;
        }
    }

    
Gets the index of a the given activity.

Params:
  • activity – The activity index.
Returns:The index if found, -1 otherwise.
/**
     * Gets the index of a the given activity.
     *
     * @param activity The activity index.
     *
     * @return The index if found, -1 otherwise.
     */
    public int getActivityIndex(ResolveInfo activity) {
        synchronized (mInstanceLock) {
            ensureConsistentState();
            List<ActivityResolveInfo> activities = mActivities;
            final int activityCount = activities.size();
            for (int i = 0; i < activityCount; i++) {
                ActivityResolveInfo currentActivity = activities.get(i);
                if (currentActivity.resolveInfo == activity) {
                    return i;
                }
            }
            return INVALID_INDEX;
        }
    }

    
Chooses a activity to handle the current intent. This will result in
adding a historical record for that action and construct intent with
its component name set such that it can be immediately started by the
client.


Note: By calling this method the client guarantees
that the returned intent will be started. This intent is returned to
the client solely to let additional customization before the start.



See Also:
Returns:An Intent for launching the activity or null if the policy has consumed the intent or there is not current intent set via setIntent(Intent).
/**
     * Chooses a activity to handle the current intent. This will result in
     * adding a historical record for that action and construct intent with
     * its component name set such that it can be immediately started by the
     * client.
     * <p>
     * <strong>Note:</strong> By calling this method the client guarantees
     * that the returned intent will be started. This intent is returned to
     * the client solely to let additional customization before the start.
     * </p>
     *
     * @return An {@link Intent} for launching the activity or null if the
     *         policy has consumed the intent or there is not current intent
     *         set via {@link #setIntent(Intent)}.
     *
     * @see HistoricalRecord
     * @see OnChooseActivityListener
     */
    public Intent chooseActivity(int index) {
        synchronized (mInstanceLock) {
            if (mIntent == null) {
                return null;
            }

            ensureConsistentState();

            ActivityResolveInfo chosenActivity = mActivities.get(index);

            ComponentName chosenName = new ComponentName(
                    chosenActivity.resolveInfo.activityInfo.packageName,
                    chosenActivity.resolveInfo.activityInfo.name);

            Intent choiceIntent = new Intent(mIntent);
            choiceIntent.setComponent(chosenName);

            if (mActivityChoserModelPolicy != null) {
                // Do not allow the policy to change the intent.
                Intent choiceIntentCopy = new Intent(choiceIntent);
                final boolean handled = mActivityChoserModelPolicy.onChooseActivity(this,
                        choiceIntentCopy);
                if (handled) {
                    return null;
                }
            }

            HistoricalRecord historicalRecord = new HistoricalRecord(chosenName,
                    System.currentTimeMillis(), DEFAULT_HISTORICAL_RECORD_WEIGHT);
            addHisoricalRecord(historicalRecord);

            return choiceIntent;
        }
    }

    
Sets the listener for choosing an activity.

Params:
  • listener – The listener.
/**
     * Sets the listener for choosing an activity.
     *
     * @param listener The listener.
     */
    public void setOnChooseActivityListener(OnChooseActivityListener listener) {
        synchronized (mInstanceLock) {
            mActivityChoserModelPolicy = listener;
        }
    }

    
Gets the default activity, The default activity is defined as the one
with highest rank i.e. the first one in the list of activities that can
handle the intent.

See Also:
Returns:The default activity, null id not activities.
/**
     * Gets the default activity, The default activity is defined as the one
     * with highest rank i.e. the first one in the list of activities that can
     * handle the intent.
     *
     * @return The default activity, <code>null</code> id not activities.
     *
     * @see #getActivity(int)
     */
    public ResolveInfo getDefaultActivity() {
        synchronized (mInstanceLock) {
            ensureConsistentState();
            if (!mActivities.isEmpty()) {
                return mActivities.get(0).resolveInfo;
            }
        }
        return null;
    }

    
Sets the default activity. The default activity is set by adding a
historical record with weight high enough that this activity will
become the highest ranked. Such a strategy guarantees that the default
will eventually change if not used. Also the weight of the record for
setting a default is inflated with a constant amount to guarantee that
it will stay as default for awhile.

Params:
  • index – The index of the activity to set as default.
/**
     * Sets the default activity. The default activity is set by adding a
     * historical record with weight high enough that this activity will
     * become the highest ranked. Such a strategy guarantees that the default
     * will eventually change if not used. Also the weight of the record for
     * setting a default is inflated with a constant amount to guarantee that
     * it will stay as default for awhile.
     *
     * @param index The index of the activity to set as default.
     */
    public void setDefaultActivity(int index) {
        synchronized (mInstanceLock) {
            ensureConsistentState();

            ActivityResolveInfo newDefaultActivity = mActivities.get(index);
            ActivityResolveInfo oldDefaultActivity = mActivities.get(0);

            final float weight;
            if (oldDefaultActivity != null) {
                // Add a record with weight enough to boost the chosen at the top.
                weight = oldDefaultActivity.weight - newDefaultActivity.weight
                    + DEFAULT_ACTIVITY_INFLATION;
            } else {
                weight = DEFAULT_HISTORICAL_RECORD_WEIGHT;
            }

            ComponentName defaultName = new ComponentName(
                    newDefaultActivity.resolveInfo.activityInfo.packageName,
                    newDefaultActivity.resolveInfo.activityInfo.name);
            HistoricalRecord historicalRecord = new HistoricalRecord(defaultName,
                    System.currentTimeMillis(), weight);
            addHisoricalRecord(historicalRecord);
        }
    }

    
Persists the history data to the backing file if the latter was provided. Calling this method before a call to readHistoricalDataIfNeeded() throws an exception. Calling this method more than one without choosing an activity has not effect. 
Throws:
/**
     * Persists the history data to the backing file if the latter
     * was provided. Calling this method before a call to {@link #readHistoricalDataIfNeeded()}
     * throws an exception. Calling this method more than one without choosing an
     * activity has not effect.
     *
     * @throws IllegalStateException If this method is called before a call to
     *         {@link #readHistoricalDataIfNeeded()}.
     */
    private void persistHistoricalDataIfNeeded() {
        if (!mReadShareHistoryCalled) {
            throw new IllegalStateException("No preceding call to #readHistoricalData");
        }
        if (!mHistoricalRecordsChanged) {
            return;
        }
        mHistoricalRecordsChanged = false;
        if (!TextUtils.isEmpty(mHistoryFileName)) {
            new PersistHistoryAsyncTask().executeOnExecutor(AsyncTask.SERIAL_EXECUTOR,
                    new ArrayList<HistoricalRecord>(mHistoricalRecords), mHistoryFileName);
        }
    }

    
Sets the sorter for ordering activities based on historical data and an intent.

Params:
  • activitySorter – The sorter.
See Also:
/**
     * Sets the sorter for ordering activities based on historical data and an intent.
     *
     * @param activitySorter The sorter.
     *
     * @see ActivitySorter
     */
    public void setActivitySorter(ActivitySorter activitySorter) {
        synchronized (mInstanceLock) {
            if (mActivitySorter == activitySorter) {
                return;
            }
            mActivitySorter = activitySorter;
            if (sortActivitiesIfNeeded()) {
                notifyChanged();
            }
        }
    }

    
Sets the maximal size of the historical data. Defaults to DEFAULT_HISTORY_MAX_LENGTH 

  Note: Setting this property will immediately
  enforce the specified max history size by dropping enough old
  historical records to enforce the desired size. Thus, any
  records that exceed the history size will be discarded and
  irreversibly lost.



Params:
  • historyMaxSize – The max history size.
/**
     * Sets the maximal size of the historical data. Defaults to
     * {@link #DEFAULT_HISTORY_MAX_LENGTH}
     * <p>
     *   <strong>Note:</strong> Setting this property will immediately
     *   enforce the specified max history size by dropping enough old
     *   historical records to enforce the desired size. Thus, any
     *   records that exceed the history size will be discarded and
     *   irreversibly lost.
     * </p>
     *
     * @param historyMaxSize The max history size.
     */
    public void setHistoryMaxSize(int historyMaxSize) {
        synchronized (mInstanceLock) {
            if (mHistoryMaxSize == historyMaxSize) {
                return;
            }
            mHistoryMaxSize = historyMaxSize;
            pruneExcessiveHistoricalRecordsIfNeeded();
            if (sortActivitiesIfNeeded()) {
                notifyChanged();
            }
        }
    }

    
Gets the history max size.

Returns:The history max size.
/**
     * Gets the history max size.
     *
     * @return The history max size.
     */
    public int getHistoryMaxSize() {
        synchronized (mInstanceLock) {
            return mHistoryMaxSize;
        }
    }

    
Gets the history size.

Returns:The history size.
/**
     * Gets the history size.
     *
     * @return The history size.
     */
    public int getHistorySize() {
        synchronized (mInstanceLock) {
            ensureConsistentState();
            return mHistoricalRecords.size();
        }
    }

    @Override
    protected void finalize() throws Throwable {
        super.finalize();
        mPackageMonitor.unregister();
    }

    
Ensures the model is in a consistent state which is the
activities for the current intent have been loaded, the
most recent history has been read, and the activities
are sorted.

/**
     * Ensures the model is in a consistent state which is the
     * activities for the current intent have been loaded, the
     * most recent history has been read, and the activities
     * are sorted.
     */
    private void ensureConsistentState() {
        boolean stateChanged = loadActivitiesIfNeeded();
        stateChanged |= readHistoricalDataIfNeeded();
        pruneExcessiveHistoricalRecordsIfNeeded();
        if (stateChanged) {
            sortActivitiesIfNeeded();
            notifyChanged();
        }
    }

    
Sorts the activities if necessary which is if there is a
sorter, there are some activities to sort, and there is some
historical data.

Returns:Whether sorting was performed.
/**
     * Sorts the activities if necessary which is if there is a
     * sorter, there are some activities to sort, and there is some
     * historical data.
     *
     * @return Whether sorting was performed.
     */
    private boolean sortActivitiesIfNeeded() {
        if (mActivitySorter != null && mIntent != null
                && !mActivities.isEmpty() && !mHistoricalRecords.isEmpty()) {
            mActivitySorter.sort(mIntent, mActivities,
                    Collections.unmodifiableList(mHistoricalRecords));
            return true;
        }
        return false;
    }

    
Loads the activities for the current intent if needed which is
if they are not already loaded for the current intent.

Returns:Whether loading was performed.
/**
     * Loads the activities for the current intent if needed which is
     * if they are not already loaded for the current intent.
     *
     * @return Whether loading was performed.
     */
    private boolean loadActivitiesIfNeeded() {
        if (mReloadActivities && mIntent != null) {
            mReloadActivities = false;
            mActivities.clear();
            List<ResolveInfo> resolveInfos = mContext.getPackageManager()
                    .queryIntentActivities(mIntent, 0);
            final int resolveInfoCount = resolveInfos.size();
            for (int i = 0; i < resolveInfoCount; i++) {
                ResolveInfo resolveInfo = resolveInfos.get(i);
                ActivityInfo activityInfo = resolveInfo.activityInfo;
                if (ActivityManager.checkComponentPermission(activityInfo.permission,
                        android.os.Process.myUid(), activityInfo.applicationInfo.uid,
                        activityInfo.exported) == PackageManager.PERMISSION_GRANTED) {
                    mActivities.add(new ActivityResolveInfo(resolveInfo));
                }
            }
            return true;
        }
        return false;
    }

    
Reads the historical data if necessary which is it has
changed, there is a history file, and there is not persist
in progress.

Returns:Whether reading was performed.
/**
     * Reads the historical data if necessary which is it has
     * changed, there is a history file, and there is not persist
     * in progress.
     *
     * @return Whether reading was performed.
     */
    private boolean readHistoricalDataIfNeeded() {
        if (mCanReadHistoricalData && mHistoricalRecordsChanged &&
                !TextUtils.isEmpty(mHistoryFileName)) {
            mCanReadHistoricalData = false;
            mReadShareHistoryCalled = true;
            readHistoricalDataImpl();
            return true;
        }
        return false;
    }

    
Adds a historical record.

Params:
  • historicalRecord – The record to add.
Returns:True if the record was added.
/**
     * Adds a historical record.
     *
     * @param historicalRecord The record to add.
     * @return True if the record was added.
     */
    private boolean addHisoricalRecord(HistoricalRecord historicalRecord) {
        final boolean added = mHistoricalRecords.add(historicalRecord);
        if (added) {
            mHistoricalRecordsChanged = true;
            pruneExcessiveHistoricalRecordsIfNeeded();
            persistHistoricalDataIfNeeded();
            sortActivitiesIfNeeded();
            notifyChanged();
        }
        return added;
    }

    
Prunes older excessive records to guarantee maxHistorySize.

/**
     * Prunes older excessive records to guarantee maxHistorySize.
     */
    private void pruneExcessiveHistoricalRecordsIfNeeded() {
        final int pruneCount = mHistoricalRecords.size() - mHistoryMaxSize;
        if (pruneCount <= 0) {
            return;
        }
        mHistoricalRecordsChanged = true;
        for (int i = 0; i < pruneCount; i++) {
            HistoricalRecord prunedRecord = mHistoricalRecords.remove(0);
            if (DEBUG) {
                Log.i(LOG_TAG, "Pruned: " + prunedRecord);
            }
        }
    }

    
Represents a record in the history.

/**
     * Represents a record in the history.
     */
    public final static class HistoricalRecord {

        
The activity name.

/**
         * The activity name.
         */
        public final ComponentName activity;

        
The choice time.

/**
         * The choice time.
         */
        public final long time;

        
The record weight.

/**
         * The record weight.
         */
        public final float weight;

        
Creates a new instance.

Params:
  • activityName – The activity component name flattened to string.
  • time – The time the activity was chosen.
  • weight – The weight of the record.
/**
         * Creates a new instance.
         *
         * @param activityName The activity component name flattened to string.
         * @param time The time the activity was chosen.
         * @param weight The weight of the record.
         */
        public HistoricalRecord(String activityName, long time, float weight) {
            this(ComponentName.unflattenFromString(activityName), time, weight);
        }

        
Creates a new instance.

Params:
  • activityName – The activity name.
  • time – The time the activity was chosen.
  • weight – The weight of the record.
/**
         * Creates a new instance.
         *
         * @param activityName The activity name.
         * @param time The time the activity was chosen.
         * @param weight The weight of the record.
         */
        public HistoricalRecord(ComponentName activityName, long time, float weight) {
            this.activity = activityName;
            this.time = time;
            this.weight = weight;
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + ((activity == null) ? 0 : activity.hashCode());
            result = prime * result + (int) (time ^ (time >>> 32));
            result = prime * result + Float.floatToIntBits(weight);
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj) {
                return true;
            }
            if (obj == null) {
                return false;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            HistoricalRecord other = (HistoricalRecord) obj;
            if (activity == null) {
                if (other.activity != null) {
                    return false;
                }
            } else if (!activity.equals(other.activity)) {
                return false;
            }
            if (time != other.time) {
                return false;
            }
            if (Float.floatToIntBits(weight) != Float.floatToIntBits(other.weight)) {
                return false;
            }
            return true;
        }

        @Override
        public String toString() {
            StringBuilder builder = new StringBuilder();
            builder.append("[");
            builder.append("; activity:").append(activity);
            builder.append("; time:").append(time);
            builder.append("; weight:").append(new BigDecimal(weight));
            builder.append("]");
            return builder.toString();
        }
    }

    
Represents an activity.

/**
     * Represents an activity.
     */
    public final class ActivityResolveInfo implements Comparable<ActivityResolveInfo> {

        
The ResolveInfo of the activity. 
/**
         * The {@link ResolveInfo} of the activity.
         */
        public final ResolveInfo resolveInfo;

        
Weight of the activity. Useful for sorting.

/**
         * Weight of the activity. Useful for sorting.
         */
        public float weight;

        
Creates a new instance.

Params:
/**
         * Creates a new instance.
         *
         * @param resolveInfo activity {@link ResolveInfo}.
         */
        public ActivityResolveInfo(ResolveInfo resolveInfo) {
            this.resolveInfo = resolveInfo;
        }

        @Override
        public int hashCode() {
            return 31 + Float.floatToIntBits(weight);
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj) {
                return true;
            }
            if (obj == null) {
                return false;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            ActivityResolveInfo other = (ActivityResolveInfo) obj;
            if (Float.floatToIntBits(weight) != Float.floatToIntBits(other.weight)) {
                return false;
            }
            return true;
        }

        public int compareTo(ActivityResolveInfo another) {
             return  Float.floatToIntBits(another.weight) - Float.floatToIntBits(weight);
        }

        @Override
        public String toString() {
            StringBuilder builder = new StringBuilder();
            builder.append("[");
            builder.append("resolveInfo:").append(resolveInfo.toString());
            builder.append("; weight:").append(new BigDecimal(weight));
            builder.append("]");
            return builder.toString();
        }
    }

    
Default activity sorter implementation.

/**
     * Default activity sorter implementation.
     */
    private final class DefaultSorter implements ActivitySorter {
        private static final float WEIGHT_DECAY_COEFFICIENT = 0.95f;

        private final Map<ComponentName, ActivityResolveInfo> mPackageNameToActivityMap =
                new HashMap<ComponentName, ActivityResolveInfo>();

        public void sort(Intent intent, List<ActivityResolveInfo> activities,
                List<HistoricalRecord> historicalRecords) {
            Map<ComponentName, ActivityResolveInfo> componentNameToActivityMap =
                    mPackageNameToActivityMap;
            componentNameToActivityMap.clear();

            final int activityCount = activities.size();
            for (int i = 0; i < activityCount; i++) {
                ActivityResolveInfo activity = activities.get(i);
                activity.weight = 0.0f;
                ComponentName componentName = new ComponentName(
                        activity.resolveInfo.activityInfo.packageName,
                        activity.resolveInfo.activityInfo.name);
                componentNameToActivityMap.put(componentName, activity);
            }

            final int lastShareIndex = historicalRecords.size() - 1;
            float nextRecordWeight = 1;
            for (int i = lastShareIndex; i >= 0; i--) {
                HistoricalRecord historicalRecord = historicalRecords.get(i);
                ComponentName componentName = historicalRecord.activity;
                ActivityResolveInfo activity = componentNameToActivityMap.get(componentName);
                if (activity != null) {
                    activity.weight += historicalRecord.weight * nextRecordWeight;
                    nextRecordWeight = nextRecordWeight * WEIGHT_DECAY_COEFFICIENT;
                }
            }

            Collections.sort(activities);

            if (DEBUG) {
                for (int i = 0; i < activityCount; i++) {
                    Log.i(LOG_TAG, "Sorted: " + activities.get(i));
                }
            }
        }
    }

    private void readHistoricalDataImpl() {
        FileInputStream fis = null;
        try {
            fis = mContext.openFileInput(mHistoryFileName);
        } catch (FileNotFoundException fnfe) {
            if (DEBUG) {
                Log.i(LOG_TAG, "Could not open historical records file: " + mHistoryFileName);
            }
            return;
        }
        try {
            XmlPullParser parser = Xml.newPullParser();
            parser.setInput(fis, StandardCharsets.UTF_8.name());

            int type = XmlPullParser.START_DOCUMENT;
            while (type != XmlPullParser.END_DOCUMENT && type != XmlPullParser.START_TAG) {
                type = parser.next();
            }

            if (!TAG_HISTORICAL_RECORDS.equals(parser.getName())) {
                throw new XmlPullParserException("Share records file does not start with "
                        + TAG_HISTORICAL_RECORDS + " tag.");
            }

            List<HistoricalRecord> historicalRecords = mHistoricalRecords;
            historicalRecords.clear();

            while (true) {
                type = parser.next();
                if (type == XmlPullParser.END_DOCUMENT) {
                    break;
                }
                if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {
                    continue;
                }
                String nodeName = parser.getName();
                if (!TAG_HISTORICAL_RECORD.equals(nodeName)) {
                    throw new XmlPullParserException("Share records file not well-formed.");
                }

                String activity = parser.getAttributeValue(null, ATTRIBUTE_ACTIVITY);
                final long time =
                    Long.parseLong(parser.getAttributeValue(null, ATTRIBUTE_TIME));
                final float weight =
                    Float.parseFloat(parser.getAttributeValue(null, ATTRIBUTE_WEIGHT));
                 HistoricalRecord readRecord = new HistoricalRecord(activity, time, weight);
                historicalRecords.add(readRecord);

                if (DEBUG) {
                    Log.i(LOG_TAG, "Read " + readRecord.toString());
                }
            }

            if (DEBUG) {
                Log.i(LOG_TAG, "Read " + historicalRecords.size() + " historical records.");
            }
        } catch (XmlPullParserException xppe) {
            Log.e(LOG_TAG, "Error reading historical recrod file: " + mHistoryFileName, xppe);
        } catch (IOException ioe) {
            Log.e(LOG_TAG, "Error reading historical recrod file: " + mHistoryFileName, ioe);
        } finally {
            if (fis != null) {
                try {
                    fis.close();
                } catch (IOException ioe) {
                    /* ignore */
                }
            }
        }
    }

    
Command for persisting the historical records to a file off the UI thread.

/**
     * Command for persisting the historical records to a file off the UI thread.
     */
    private final class PersistHistoryAsyncTask extends AsyncTask<Object, Void, Void> {

        @Override
        @SuppressWarnings("unchecked")
        public Void doInBackground(Object... args) {
            List<HistoricalRecord> historicalRecords = (List<HistoricalRecord>) args[0];
            String hostoryFileName = (String) args[1];

            FileOutputStream fos = null;

            try {
                fos = mContext.openFileOutput(hostoryFileName, Context.MODE_PRIVATE);
            } catch (FileNotFoundException fnfe) {
                Log.e(LOG_TAG, "Error writing historical recrod file: " + hostoryFileName, fnfe);
                return null;
            }

            XmlSerializer serializer = Xml.newSerializer();

            try {
                serializer.setOutput(fos, null);
                serializer.startDocument(StandardCharsets.UTF_8.name(), true);
                serializer.startTag(null, TAG_HISTORICAL_RECORDS);

                final int recordCount = historicalRecords.size();
                for (int i = 0; i < recordCount; i++) {
                    HistoricalRecord record = historicalRecords.remove(0);
                    serializer.startTag(null, TAG_HISTORICAL_RECORD);
                    serializer.attribute(null, ATTRIBUTE_ACTIVITY,
                            record.activity.flattenToString());
                    serializer.attribute(null, ATTRIBUTE_TIME, String.valueOf(record.time));
                    serializer.attribute(null, ATTRIBUTE_WEIGHT, String.valueOf(record.weight));
                    serializer.endTag(null, TAG_HISTORICAL_RECORD);
                    if (DEBUG) {
                        Log.i(LOG_TAG, "Wrote " + record.toString());
                    }
                }

                serializer.endTag(null, TAG_HISTORICAL_RECORDS);
                serializer.endDocument();

                if (DEBUG) {
                    Log.i(LOG_TAG, "Wrote " + recordCount + " historical records.");
                }
            } catch (IllegalArgumentException iae) {
                Log.e(LOG_TAG, "Error writing historical recrod file: " + mHistoryFileName, iae);
            } catch (IllegalStateException ise) {
                Log.e(LOG_TAG, "Error writing historical recrod file: " + mHistoryFileName, ise);
            } catch (IOException ioe) {
                Log.e(LOG_TAG, "Error writing historical recrod file: " + mHistoryFileName, ioe);
            } finally {
                mCanReadHistoricalData = true;
                if (fos != null) {
                    try {
                        fos.close();
                    } catch (IOException e) {
                        /* ignore */
                    }
                }
            }
            return null;
        }
    }

    
Keeps in sync the historical records and activities with the installed applications.

/**
     * Keeps in sync the historical records and activities with the installed applications.
     */
    private final class DataModelPackageMonitor extends PackageMonitor {

        @Override
        public void onSomePackagesChanged() {
            mReloadActivities = true;
        }
    }
}