https://source.android.com/ 
/*
 * Copyright (C) 2013 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.media;

import android.app.ActivityManager;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.media.session.MediaController;
import android.media.session.MediaSession;
import android.media.session.MediaSessionLegacyHelper;
import android.media.session.MediaSessionManager;
import android.media.session.PlaybackState;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.os.UserHandle;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.KeyEvent;

import java.lang.ref.WeakReference;
import java.util.List;


The RemoteController class is used to control media playback, display and update media metadata and playback status, published by applications using the RemoteControlClient class. 
 A RemoteController shall be registered through AudioManager.registerRemoteController(RemoteController) in order for the system to send media event updates to the OnClientUpdateListener listener set in the class constructor. Implement the methods of the interface to receive the information published by the active RemoteControlClient instances. 
By default an OnClientUpdateListener implementation will not receive bitmaps for album art. Use setArtworkConfiguration(int, int) to receive images as well. 
 Registration requires the OnClientUpdateListener listener to be one of the enabled notification listeners (see NotificationListenerService). 
Deprecated:Use MediaController instead.
/**
 * The RemoteController class is used to control media playback, display and update media metadata
 * and playback status, published by applications using the {@link RemoteControlClient} class.
 * <p>
 * A RemoteController shall be registered through
 * {@link AudioManager#registerRemoteController(RemoteController)} in order for the system to send
 * media event updates to the {@link OnClientUpdateListener} listener set in the class constructor.
 * Implement the methods of the interface to receive the information published by the active
 * {@link RemoteControlClient} instances.
 * <br>By default an {@link OnClientUpdateListener} implementation will not receive bitmaps for
 * album art. Use {@link #setArtworkConfiguration(int, int)} to receive images as well.
 * <p>
 * Registration requires the {@link OnClientUpdateListener} listener to be one of the enabled
 * notification listeners (see {@link android.service.notification.NotificationListenerService}).
 *
 * @deprecated Use {@link MediaController} instead.
 */
@Deprecated public final class RemoteController
{
    private final static int MAX_BITMAP_DIMENSION = 512;
    private final static String TAG = "RemoteController";
    private final static boolean DEBUG = false;
    private final static Object mInfoLock = new Object();
    private final Context mContext;
    private final int mMaxBitmapDimension;
    private MetadataEditor mMetadataEditor;

    private MediaSessionManager mSessionManager;
    private MediaSessionManager.OnActiveSessionsChangedListener mSessionListener;
    private MediaController.Callback mSessionCb = new MediaControllerCallback();

    
Synchronized on mInfoLock

/**
     * Synchronized on mInfoLock
     */
    private boolean mIsRegistered = false;
    private OnClientUpdateListener mOnClientUpdateListener;
    private PlaybackInfo mLastPlaybackInfo;
    private int mArtworkWidth = -1;
    private int mArtworkHeight = -1;
    private boolean mEnabled = true;
    // synchronized on mInfoLock, for USE_SESSION apis.
    private MediaController mCurrentSession;

    
Class constructor.

Params:
  • context – the Context, must be non-null.
  • updateListener – the listener to be called whenever new client information is available,
    must be non-null.
Throws:
/**
     * Class constructor.
     * @param context the {@link Context}, must be non-null.
     * @param updateListener the listener to be called whenever new client information is available,
     *     must be non-null.
     * @throws IllegalArgumentException
     */
    public RemoteController(Context context, OnClientUpdateListener updateListener)
            throws IllegalArgumentException {
        this(context, updateListener, null);
    }

    
Class constructor.

Params:
  • context – the Context, must be non-null.
  • updateListener – the listener to be called whenever new client information is available,
    must be non-null.
  • looper – the Looper on which to run the event loop, or null to use the current thread's looper.
Throws:
/**
     * Class constructor.
     * @param context the {@link Context}, must be non-null.
     * @param updateListener the listener to be called whenever new client information is available,
     *     must be non-null.
     * @param looper the {@link Looper} on which to run the event loop,
     *     or null to use the current thread's looper.
     * @throws java.lang.IllegalArgumentException
     */
    public RemoteController(Context context, OnClientUpdateListener updateListener, Looper looper)
            throws IllegalArgumentException {
        if (context == null) {
            throw new IllegalArgumentException("Invalid null Context");
        }
        if (updateListener == null) {
            throw new IllegalArgumentException("Invalid null OnClientUpdateListener");
        }
        if (looper != null) {
            mEventHandler = new EventHandler(this, looper);
        } else {
            Looper l = Looper.myLooper();
            if (l != null) {
                mEventHandler = new EventHandler(this, l);
            } else {
                throw new IllegalArgumentException("Calling thread not associated with a looper");
            }
        }
        mOnClientUpdateListener = updateListener;
        mContext = context;
        mSessionManager = (MediaSessionManager) context
                .getSystemService(Context.MEDIA_SESSION_SERVICE);
        mSessionListener = new TopTransportSessionListener();

        if (ActivityManager.isLowRamDeviceStatic()) {
            mMaxBitmapDimension = MAX_BITMAP_DIMENSION;
        } else {
            final DisplayMetrics dm = context.getResources().getDisplayMetrics();
            mMaxBitmapDimension = Math.max(dm.widthPixels, dm.heightPixels);
        }
    }


    
Interface definition for the callbacks to be invoked whenever media events, metadata
and playback status are available.

/**
     * Interface definition for the callbacks to be invoked whenever media events, metadata
     * and playback status are available.
     */
    public interface OnClientUpdateListener {
        
Called whenever all information, previously received through the other methods of the listener, is no longer valid and is about to be refreshed. This is typically called whenever a new RemoteControlClient has been selected by the system to have its media information published. 
Params:
  • clearing – true if there is no selected RemoteControlClient and no information
    is available.
/**
         * Called whenever all information, previously received through the other
         * methods of the listener, is no longer valid and is about to be refreshed.
         * This is typically called whenever a new {@link RemoteControlClient} has been selected
         * by the system to have its media information published.
         * @param clearing true if there is no selected RemoteControlClient and no information
         *     is available.
         */
        public void onClientChange(boolean clearing);

        
Called whenever the playback state has changed.
It is called when no information is known about the playback progress in the media and
the playback speed.

Params:
/**
         * Called whenever the playback state has changed.
         * It is called when no information is known about the playback progress in the media and
         * the playback speed.
         * @param state one of the playback states authorized
         *     in {@link RemoteControlClient#setPlaybackState(int)}.
         */
        public void onClientPlaybackStateUpdate(int state);
        
Called whenever the playback state has changed, and playback position
and speed are known.

Params:
  • state – one of the playback states authorized in RemoteControlClient.setPlaybackState(int).
  • stateChangeTimeMs – the system time at which the state change was reported, expressed in ms. Based on SystemClock.elapsedRealtime().
  • currentPosMs – a positive value for the current media playback position expressed
    in ms, a negative value if the position is temporarily unknown.
  • speed –  a value expressed as a ratio of 1x playback: 1.0f is normal playback, 2.0f is 2x, 0.5f is half-speed, -2.0f is rewind at 2x speed. 0.0f means nothing is playing (e.g. when state is RemoteControlClient.PLAYSTATE_ERROR).
/**
         * Called whenever the playback state has changed, and playback position
         * and speed are known.
         * @param state one of the playback states authorized
         *     in {@link RemoteControlClient#setPlaybackState(int)}.
         * @param stateChangeTimeMs the system time at which the state change was reported,
         *     expressed in ms. Based on {@link android.os.SystemClock#elapsedRealtime()}.
         * @param currentPosMs a positive value for the current media playback position expressed
         *     in ms, a negative value if the position is temporarily unknown.
         * @param speed  a value expressed as a ratio of 1x playback: 1.0f is normal playback,
         *    2.0f is 2x, 0.5f is half-speed, -2.0f is rewind at 2x speed. 0.0f means nothing is
         *    playing (e.g. when state is {@link RemoteControlClient#PLAYSTATE_ERROR}).
         */
        public void onClientPlaybackStateUpdate(int state, long stateChangeTimeMs,
                long currentPosMs, float speed);
        
Called whenever the transport control flags have changed.

Params:
/**
         * Called whenever the transport control flags have changed.
         * @param transportControlFlags one of the flags authorized
         *     in {@link RemoteControlClient#setTransportControlFlags(int)}.
         */
        public void onClientTransportControlUpdate(int transportControlFlags);
        
Called whenever new metadata is available. See the MediaMetadataEditor.putLong(int, long), MediaMetadataEditor.putString(int, String), MediaMetadataEditor.putBitmap(int, Bitmap), and MediaMetadataEditor.putObject(int, Object) methods for the various keys that can be queried. 
Params:
  • metadataEditor – the container of the new metadata.
/**
         * Called whenever new metadata is available.
         * See the {@link MediaMetadataEditor#putLong(int, long)},
         *  {@link MediaMetadataEditor#putString(int, String)},
         *  {@link MediaMetadataEditor#putBitmap(int, Bitmap)}, and
         *  {@link MediaMetadataEditor#putObject(int, Object)} methods for the various keys that
         *  can be queried.
         * @param metadataEditor the container of the new metadata.
         */
        public void onClientMetadataUpdate(MetadataEditor metadataEditor);
    };

    
Return the estimated playback position of the current media track or a negative value
if not available.

The value returned is estimated by the current process and may not be perfect. The time returned by this method is calculated from the last state change time based on the current play position at that time and the last known playback speed. An application may call setSynchronizationMode(int) to apply a synchronization policy that will periodically re-sync the estimated position with the RemoteControlClient.


See Also:
Returns:the current estimated playback position in milliseconds or a negative value
        if not available
/**
     * Return the estimated playback position of the current media track or a negative value
     * if not available.
     *
     * <p>The value returned is estimated by the current process and may not be perfect.
     * The time returned by this method is calculated from the last state change time based
     * on the current play position at that time and the last known playback speed.
     * An application may call {@link #setSynchronizationMode(int)} to apply
     * a synchronization policy that will periodically re-sync the estimated position
     * with the RemoteControlClient.</p>
     *
     * @return the current estimated playback position in milliseconds or a negative value
     *         if not available
     *
     * @see OnClientUpdateListener#onClientPlaybackStateUpdate(int, long, long, float)
     */
    public long getEstimatedMediaPosition() {
        synchronized (mInfoLock) {
            if (mCurrentSession != null) {
                PlaybackState state = mCurrentSession.getPlaybackState();
                if (state != null) {
                    return state.getPosition();
                }
            }
        }
        return -1;
    }


    
Send a simulated key event for a media button to be received by the current client. To simulate a key press, you must first send a KeyEvent built with a KeyEvent.ACTION_DOWN action, then another event with the KeyEvent.ACTION_UP action. 
The key event will be sent to the registered receiver (see AudioManager.registerMediaButtonEventReceiver(PendingIntent)) whose associated RemoteControlClient's metadata and playback state is published (there may be none under some circumstances). 
Params:
Throws:
Returns:true if the event was successfully sent, false otherwise.
/**
     * Send a simulated key event for a media button to be received by the current client.
     * To simulate a key press, you must first send a KeyEvent built with
     * a {@link KeyEvent#ACTION_DOWN} action, then another event with the {@link KeyEvent#ACTION_UP}
     * action.
     * <p>The key event will be sent to the registered receiver
     * (see {@link AudioManager#registerMediaButtonEventReceiver(PendingIntent)}) whose associated
     * {@link RemoteControlClient}'s metadata and playback state is published (there may be
     * none under some circumstances).
     * @param keyEvent a {@link KeyEvent} instance whose key code is one of
     *     {@link KeyEvent#KEYCODE_MUTE},
     *     {@link KeyEvent#KEYCODE_HEADSETHOOK},
     *     {@link KeyEvent#KEYCODE_MEDIA_PLAY},
     *     {@link KeyEvent#KEYCODE_MEDIA_PAUSE},
     *     {@link KeyEvent#KEYCODE_MEDIA_PLAY_PAUSE},
     *     {@link KeyEvent#KEYCODE_MEDIA_STOP},
     *     {@link KeyEvent#KEYCODE_MEDIA_NEXT},
     *     {@link KeyEvent#KEYCODE_MEDIA_PREVIOUS},
     *     {@link KeyEvent#KEYCODE_MEDIA_REWIND},
     *     {@link KeyEvent#KEYCODE_MEDIA_RECORD},
     *     {@link KeyEvent#KEYCODE_MEDIA_FAST_FORWARD},
     *     {@link KeyEvent#KEYCODE_MEDIA_CLOSE},
     *     {@link KeyEvent#KEYCODE_MEDIA_EJECT},
     *     or {@link KeyEvent#KEYCODE_MEDIA_AUDIO_TRACK}.
     * @return true if the event was successfully sent, false otherwise.
     * @throws IllegalArgumentException
     */
    public boolean sendMediaKeyEvent(KeyEvent keyEvent) throws IllegalArgumentException {
        if (!KeyEvent.isMediaKey(keyEvent.getKeyCode())) {
            throw new IllegalArgumentException("not a media key event");
        }
        synchronized (mInfoLock) {
            if (mCurrentSession != null) {
                return mCurrentSession.dispatchMediaButtonEvent(keyEvent);
            }
            return false;
        }
    }


    
Sets the new playback position.
This method can only be called on a registered RemoteController.

Params:
  • timeMs – a 0 or positive value for the new playback position, expressed in ms.
Throws:
Returns:true if the command to set the playback position was successfully sent.
/**
     * Sets the new playback position.
     * This method can only be called on a registered RemoteController.
     * @param timeMs a 0 or positive value for the new playback position, expressed in ms.
     * @return true if the command to set the playback position was successfully sent.
     * @throws IllegalArgumentException
     */
    public boolean seekTo(long timeMs) throws IllegalArgumentException {
        if (!mEnabled) {
            Log.e(TAG, "Cannot use seekTo() from a disabled RemoteController");
            return false;
        }
        if (timeMs < 0) {
            throw new IllegalArgumentException("illegal negative time value");
        }
        synchronized (mInfoLock) {
            if (mCurrentSession != null) {
                mCurrentSession.getTransportControls().seekTo(timeMs);
            }
        }
        return true;
    }


    
Params:
  • wantBitmap – 
  • width – 
  • height – 
Throws:
@hide
Returns:true if successful
/**
     * @hide
     * @param wantBitmap
     * @param width
     * @param height
     * @return true if successful
     * @throws IllegalArgumentException
     */
    public boolean setArtworkConfiguration(boolean wantBitmap, int width, int height)
            throws IllegalArgumentException {
        synchronized (mInfoLock) {
            if (wantBitmap) {
                if ((width > 0) && (height > 0)) {
                    if (width > mMaxBitmapDimension) { width = mMaxBitmapDimension; }
                    if (height > mMaxBitmapDimension) { height = mMaxBitmapDimension; }
                    mArtworkWidth = width;
                    mArtworkHeight = height;
                } else {
                    throw new IllegalArgumentException("Invalid dimensions");
                }
            } else {
                mArtworkWidth = -1;
                mArtworkHeight = -1;
            }
        }
        return true;
    }

    
Set the maximum artwork image dimensions to be received in the metadata.
No bitmaps will be received unless this has been specified.

Params:
  • width – the maximum width in pixels
  • height –  the maximum height in pixels
Throws:
Returns:true if the artwork dimension was successfully set.
/**
     * Set the maximum artwork image dimensions to be received in the metadata.
     * No bitmaps will be received unless this has been specified.
     * @param width the maximum width in pixels
     * @param height  the maximum height in pixels
     * @return true if the artwork dimension was successfully set.
     * @throws IllegalArgumentException
     */
    public boolean setArtworkConfiguration(int width, int height) throws IllegalArgumentException {
        return setArtworkConfiguration(true, width, height);
    }

    
Prevents this RemoteController from receiving artwork images.

Returns:true if receiving artwork images was successfully disabled.
/**
     * Prevents this RemoteController from receiving artwork images.
     * @return true if receiving artwork images was successfully disabled.
     */
    public boolean clearArtworkConfiguration() {
        return setArtworkConfiguration(false, -1, -1);
    }


    
Default playback position synchronization mode where the RemoteControlClient is not
asked regularly for its playback position to see if it has drifted from the estimated
position.

/**
     * Default playback position synchronization mode where the RemoteControlClient is not
     * asked regularly for its playback position to see if it has drifted from the estimated
     * position.
     */
    public static final int POSITION_SYNCHRONIZATION_NONE = 0;

    
The playback position synchronization mode where the RemoteControlClient instances which
expose their playback position to the framework, will be regularly polled to check
whether any drift has been noticed between their estimated position and the one they report.
Note that this mode should only ever be used when needing to display very accurate playback
position, as regularly polling a RemoteControlClient for its position may have an impact
on battery life (if applicable) when this query will trigger network transactions in the
case of remote playback.

/**
     * The playback position synchronization mode where the RemoteControlClient instances which
     * expose their playback position to the framework, will be regularly polled to check
     * whether any drift has been noticed between their estimated position and the one they report.
     * Note that this mode should only ever be used when needing to display very accurate playback
     * position, as regularly polling a RemoteControlClient for its position may have an impact
     * on battery life (if applicable) when this query will trigger network transactions in the
     * case of remote playback.
     */
    public static final int POSITION_SYNCHRONIZATION_CHECK = 1;

    
Set the playback position synchronization mode.
Must be called on a registered RemoteController.

Params:
Throws:
Returns:true if the synchronization mode was successfully set.
/**
     * Set the playback position synchronization mode.
     * Must be called on a registered RemoteController.
     * @param sync {@link #POSITION_SYNCHRONIZATION_NONE} or {@link #POSITION_SYNCHRONIZATION_CHECK}
     * @return true if the synchronization mode was successfully set.
     * @throws IllegalArgumentException
     */
    public boolean setSynchronizationMode(int sync) throws IllegalArgumentException {
        if ((sync != POSITION_SYNCHRONIZATION_NONE) && (sync != POSITION_SYNCHRONIZATION_CHECK)) {
            throw new IllegalArgumentException("Unknown synchronization mode " + sync);
        }
        if (!mIsRegistered) {
            Log.e(TAG, "Cannot set synchronization mode on an unregistered RemoteController");
            return false;
        }
        // deprecated, no-op
        return true;
    }


    
Creates a MetadataEditor for updating metadata values of the editable keys of the current RemoteControlClient. This method can only be called on a registered RemoteController. 
Returns:a new MetadataEditor instance.
/**
     * Creates a {@link MetadataEditor} for updating metadata values of the editable keys of
     * the current {@link RemoteControlClient}.
     * This method can only be called on a registered RemoteController.
     * @return a new MetadataEditor instance.
     */
    public MetadataEditor editMetadata() {
        MetadataEditor editor = new MetadataEditor();
        editor.mEditorMetadata = new Bundle();
        editor.mEditorArtwork = null;
        editor.mMetadataChanged = true;
        editor.mArtworkChanged = true;
        editor.mEditableKeys = 0;
        return editor;
    }

    
A class to read the metadata published by a RemoteControlClient, or send a RemoteControlClient new values for keys that can be edited. 
/**
     * A class to read the metadata published by a {@link RemoteControlClient}, or send a
     * {@link RemoteControlClient} new values for keys that can be edited.
     */
    public class MetadataEditor extends MediaMetadataEditor {
        
@hide
/**
         * @hide
         */
        protected MetadataEditor() { }

        
@hide
/**
         * @hide
         */
        protected MetadataEditor(Bundle metadata, long editableKeys) {
            mEditorMetadata = metadata;
            mEditableKeys = editableKeys;

            mEditorArtwork = (Bitmap) metadata.getParcelable(
                    String.valueOf(MediaMetadataEditor.BITMAP_KEY_ARTWORK));
            if (mEditorArtwork != null) {
                cleanupBitmapFromBundle(MediaMetadataEditor.BITMAP_KEY_ARTWORK);
            }

            mMetadataChanged = true;
            mArtworkChanged = true;
            mApplied = false;
        }

        private void cleanupBitmapFromBundle(int key) {
            if (METADATA_KEYS_TYPE.get(key, METADATA_TYPE_INVALID) == METADATA_TYPE_BITMAP) {
                mEditorMetadata.remove(String.valueOf(key));
            }
        }

        
Applies all of the metadata changes that have been set since the MediaMetadataEditor instance was created with RemoteController.editMetadata() or since MediaMetadataEditor.clear() was called. 
/**
         * Applies all of the metadata changes that have been set since the MediaMetadataEditor
         * instance was created with {@link RemoteController#editMetadata()}
         * or since {@link #clear()} was called.
         */
        public synchronized void apply() {
            // "applying" a metadata bundle in RemoteController is only for sending edited
            // key values back to the RemoteControlClient, so here we only care about the only
            // editable key we support: RATING_KEY_BY_USER
            if (!mMetadataChanged) {
                return;
            }
            synchronized (mInfoLock) {
                if (mCurrentSession != null) {
                    if (mEditorMetadata.containsKey(
                            String.valueOf(MediaMetadataEditor.RATING_KEY_BY_USER))) {
                        Rating rating = (Rating) getObject(
                                MediaMetadataEditor.RATING_KEY_BY_USER, null);
                        if (rating != null) {
                            mCurrentSession.getTransportControls().setRating(rating);
                        }
                    }
                }
            }
            // NOT setting mApplied to true as this type of MetadataEditor will be applied
            // multiple times, whenever the user of a RemoteController needs to change the
            // metadata (e.g. user changes the rating of a song more than once during playback)
            mApplied = false;
        }

    }

    
This receives updates when the current session changes. This is
registered to receive the updates on the handler thread so it can call
directly into the appropriate methods.

/**
     * This receives updates when the current session changes. This is
     * registered to receive the updates on the handler thread so it can call
     * directly into the appropriate methods.
     */
    private class MediaControllerCallback extends MediaController.Callback {
        @Override
        public void onPlaybackStateChanged(PlaybackState state) {
            onNewPlaybackState(state);
        }

        @Override
        public void onMetadataChanged(MediaMetadata metadata) {
            onNewMediaMetadata(metadata);
        }
    }

    
Listens for changes to the active session stack and replaces the
currently tracked session if it has changed.

/**
     * Listens for changes to the active session stack and replaces the
     * currently tracked session if it has changed.
     */
    private class TopTransportSessionListener implements
            MediaSessionManager.OnActiveSessionsChangedListener {

        @Override
        public void onActiveSessionsChanged(List<MediaController> controllers) {
            int size = controllers.size();
            for (int i = 0; i < size; i++) {
                MediaController controller = controllers.get(i);
                long flags = controller.getFlags();
                // We only care about sessions that handle transport controls,
                // which will be true for apps using RCC
                if ((flags & MediaSession.FLAG_HANDLES_TRANSPORT_CONTROLS) != 0) {
                    updateController(controller);
                    return;
                }
            }
            updateController(null);
        }

    }

    //==================================================
    // Event handling
    private final EventHandler mEventHandler;
    private final static int MSG_CLIENT_CHANGE      = 0;
    private final static int MSG_NEW_PLAYBACK_STATE = 1;
    private final static int MSG_NEW_MEDIA_METADATA = 2;

    private class EventHandler extends Handler {

        public EventHandler(RemoteController rc, Looper looper) {
            super(looper);
        }

        @Override
        public void handleMessage(Message msg) {
            switch(msg.what) {
                case MSG_CLIENT_CHANGE:
                    onClientChange(msg.arg2 == 1);
                    break;
                case MSG_NEW_PLAYBACK_STATE:
                    onNewPlaybackState((PlaybackState) msg.obj);
                    break;
                case MSG_NEW_MEDIA_METADATA:
                    onNewMediaMetadata((MediaMetadata) msg.obj);
                    break;
                default:
                    Log.e(TAG, "unknown event " + msg.what);
            }
        }
    }

    
@hide
/**
     * @hide
     */
    void startListeningToSessions() {
        final ComponentName listenerComponent = new ComponentName(mContext,
                mOnClientUpdateListener.getClass());
        Handler handler = null;
        if (Looper.myLooper() == null) {
            handler = new Handler(Looper.getMainLooper());
        }
        mSessionManager.addOnActiveSessionsChangedListener(mSessionListener, listenerComponent,
                UserHandle.myUserId(), handler);
        mSessionListener.onActiveSessionsChanged(mSessionManager
                .getActiveSessions(listenerComponent));
        if (DEBUG) {
            Log.d(TAG, "Registered session listener with component " + listenerComponent
                    + " for user " + UserHandle.myUserId());
        }
    }

    
@hide
/**
     * @hide
     */
    void stopListeningToSessions() {
        mSessionManager.removeOnActiveSessionsChangedListener(mSessionListener);
        if (DEBUG) {
            Log.d(TAG, "Unregistered session listener for user "
                    + UserHandle.myUserId());
        }
    }

    
If the msg is already queued, replace it with this one. 
/** If the msg is already queued, replace it with this one. */
    private static final int SENDMSG_REPLACE = 0;
    
If the msg is already queued, ignore this one and leave the old. 
/** If the msg is already queued, ignore this one and leave the old. */
    private static final int SENDMSG_NOOP = 1;
    
If the msg is already queued, queue this one and leave the old. 
/** If the msg is already queued, queue this one and leave the old. */
    private static final int SENDMSG_QUEUE = 2;

    private static void sendMsg(Handler handler, int msg, int existingMsgPolicy,
            int arg1, int arg2, Object obj, int delayMs) {
        if (handler == null) {
            Log.e(TAG, "null event handler, will not deliver message " + msg);
            return;
        }
        if (existingMsgPolicy == SENDMSG_REPLACE) {
            handler.removeMessages(msg);
        } else if (existingMsgPolicy == SENDMSG_NOOP && handler.hasMessages(msg)) {
            return;
        }
        handler.sendMessageDelayed(handler.obtainMessage(msg, arg1, arg2, obj), delayMs);
    }

    private void onClientChange(boolean clearing) {
        final OnClientUpdateListener l;
        synchronized(mInfoLock) {
            l = mOnClientUpdateListener;
            mMetadataEditor = null;
        }
        if (l != null) {
            l.onClientChange(clearing);
        }
    }

    private void updateController(MediaController controller) {
        if (DEBUG) {
            Log.d(TAG, "Updating controller to " + controller + " previous controller is "
                    + mCurrentSession);
        }
        synchronized (mInfoLock) {
            if (controller == null) {
                if (mCurrentSession != null) {
                    mCurrentSession.unregisterCallback(mSessionCb);
                    mCurrentSession = null;
                    sendMsg(mEventHandler, MSG_CLIENT_CHANGE, SENDMSG_REPLACE,
                            0 /* arg1 ignored */, 1 /* clearing */, null /* obj */, 0 /* delay */);
                }
            } else if (mCurrentSession == null
                    || !controller.getSessionToken()
                            .equals(mCurrentSession.getSessionToken())) {
                if (mCurrentSession != null) {
                    mCurrentSession.unregisterCallback(mSessionCb);
                }
                sendMsg(mEventHandler, MSG_CLIENT_CHANGE, SENDMSG_REPLACE,
                        0 /* arg1 ignored */, 0 /* clearing */, null /* obj */, 0 /* delay */);
                mCurrentSession = controller;
                mCurrentSession.registerCallback(mSessionCb, mEventHandler);

                PlaybackState state = controller.getPlaybackState();
                sendMsg(mEventHandler, MSG_NEW_PLAYBACK_STATE, SENDMSG_REPLACE,
                        0 /* arg1 ignored */, 0 /* arg2 ignored */, state /* obj */, 0 /* delay */);

                MediaMetadata metadata = controller.getMetadata();
                sendMsg(mEventHandler, MSG_NEW_MEDIA_METADATA, SENDMSG_REPLACE,
                        0 /* arg1 ignored */, 0 /* arg2 ignored*/, metadata /* obj */, 0 /*delay*/);
            }
            // else same controller, no need to update
        }
    }

    private void onNewPlaybackState(PlaybackState state) {
        final OnClientUpdateListener l;
        synchronized (mInfoLock) {
            l = this.mOnClientUpdateListener;
        }
        if (l != null) {
            int playstate = state == null ? RemoteControlClient.PLAYSTATE_NONE : PlaybackState
                    .getRccStateFromState(state.getState());
            if (state == null || state.getPosition() == PlaybackState.PLAYBACK_POSITION_UNKNOWN) {
                l.onClientPlaybackStateUpdate(playstate);
            } else {
                l.onClientPlaybackStateUpdate(playstate, state.getLastPositionUpdateTime(),
                        state.getPosition(), state.getPlaybackSpeed());
            }
            if (state != null) {
                l.onClientTransportControlUpdate(
                        PlaybackState.getRccControlFlagsFromActions(state.getActions()));
            }
        }
    }

    private void onNewMediaMetadata(MediaMetadata metadata) {
        if (metadata == null) {
            // RemoteController only handles non-null metadata
            return;
        }
        final OnClientUpdateListener l;
        final MetadataEditor metadataEditor;
        // prepare the received Bundle to be used inside a MetadataEditor
        synchronized(mInfoLock) {
            l = mOnClientUpdateListener;
            boolean canRate = mCurrentSession != null
                    && mCurrentSession.getRatingType() != Rating.RATING_NONE;
            long editableKeys = canRate ? MediaMetadataEditor.RATING_KEY_BY_USER : 0;
            Bundle legacyMetadata = MediaSessionLegacyHelper.getOldMetadata(metadata,
                    mArtworkWidth, mArtworkHeight);
            mMetadataEditor = new MetadataEditor(legacyMetadata, editableKeys);
            metadataEditor = mMetadataEditor;
        }
        if (l != null) {
            l.onClientMetadataUpdate(metadataEditor);
        }
    }

    //==================================================
    private static class PlaybackInfo {
        int mState;
        long mStateChangeTimeMs;
        long mCurrentPosMs;
        float mSpeed;

        PlaybackInfo(int state, long stateChangeTimeMs, long currentPosMs, float speed) {
            mState = state;
            mStateChangeTimeMs = stateChangeTimeMs;
            mCurrentPosMs = currentPosMs;
            mSpeed = speed;
        }
    }

    
@hide
Used by AudioManager to access user listener receiving the client update notifications
Returns:
/**
     * @hide
     * Used by AudioManager to access user listener receiving the client update notifications
     * @return
     */
    OnClientUpdateListener getUpdateListener() {
        return mOnClientUpdateListener;
    }
}