xref: /frameworks/base/media/java/android/media/session/MediaSessionManager.java

/*
 * Copyright (C) 2014 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.session;

import android.annotation.CallbackExecutor;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.RequiresPermission;
import android.annotation.SystemApi;
import android.annotation.SystemService;
import android.content.ComponentName;
import android.content.Context;
import android.media.AudioManager;
import android.media.IRemoteVolumeController;
import android.media.ISessionTokensListener;
import android.media.MediaSession2;
import android.media.MediaSessionService2;
import android.media.SessionToken2;
import android.media.browse.MediaBrowser;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.RemoteException;
import android.os.ResultReceiver;
import android.os.ServiceManager;
import android.os.UserHandle;
import android.service.media.MediaBrowserService;
import android.service.notification.NotificationListenerService;
import android.text.TextUtils;
import android.util.ArrayMap;
import android.util.Log;
import android.view.KeyEvent;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.Executor;

/**
 * Provides support for interacting with {@link MediaSession media sessions}
 * that applications have published to express their ongoing media playback
 * state.
 *
 * @see MediaSession
 * @see MediaController
 */
@SystemService(Context.MEDIA_SESSION_SERVICE)
public final class MediaSessionManager {
    private static final String TAG = "SessionManager";

    /**
     * Used by IOnMediaKeyListener to indicate that the media key event isn't handled.
     * @hide
     */
    public static final int RESULT_MEDIA_KEY_NOT_HANDLED = 0;

    /**
     * Used by IOnMediaKeyListener to indicate that the media key event is handled.
     * @hide
     */
    public static final int RESULT_MEDIA_KEY_HANDLED = 1;

    private final ArrayMap<OnActiveSessionsChangedListener, SessionsChangedWrapper> mListeners
            = new ArrayMap<OnActiveSessionsChangedListener, SessionsChangedWrapper>();
    private final ArrayMap<OnSessionTokensChangedListener, SessionTokensChangedWrapper>
            mSessionTokensListener = new ArrayMap<>();
    private final Object mLock = new Object();
    private final ISessionManager mService;

    private Context mContext;

    private CallbackImpl mCallback;
    private OnVolumeKeyLongPressListenerImpl mOnVolumeKeyLongPressListener;
    private OnMediaKeyListenerImpl mOnMediaKeyListener;

    /**
     * @hide
     */
    public MediaSessionManager(Context context) {
        // Consider rewriting like DisplayManagerGlobal
        // Decide if we need context
        mContext = context;
        IBinder b = ServiceManager.getService(Context.MEDIA_SESSION_SERVICE);
        mService = ISessionManager.Stub.asInterface(b);
    }

    /**
     * Create a new session in the system and get the binder for it.
     *
     * @param tag A short name for debugging purposes.
     * @return The binder object from the system
     * @hide
     */
    public @NonNull ISession createSession(@NonNull MediaSession.CallbackStub cbStub,
            @NonNull String tag, int userId) throws RemoteException {
        return mService.createSession(mContext.getPackageName(), cbStub, tag, userId);
    }

    /**
     * Get a list of controllers for all ongoing sessions. The controllers will
     * be provided in priority order with the most important controller at index
     * 0.
     * <p>
     * This requires the android.Manifest.permission.MEDIA_CONTENT_CONTROL
     * permission be held by the calling app. You may also retrieve this list if
     * your app is an enabled notification listener using the
     * {@link NotificationListenerService} APIs, in which case you must pass the
     * {@link ComponentName} of your enabled listener.
     *
     * @param notificationListener The enabled notification listener component.
     *            May be null.
     * @return A list of controllers for ongoing sessions.
     */
    public @NonNull List<MediaController> getActiveSessions(
            @Nullable ComponentName notificationListener) {
        return getActiveSessionsForUser(notificationListener, UserHandle.myUserId());
    }

    /**
     * Get active sessions for a specific user. To retrieve actions for a user
     * other than your own you must hold the
     * {@link android.Manifest.permission#INTERACT_ACROSS_USERS_FULL} permission
     * in addition to any other requirements. If you are an enabled notification
     * listener you may only get sessions for the users you are enabled for.
     *
     * @param notificationListener The enabled notification listener component.
     *            May be null.
     * @param userId The user id to fetch sessions for.
     * @return A list of controllers for ongoing sessions.
     * @hide
     */
    public @NonNull List<MediaController> getActiveSessionsForUser(
            @Nullable ComponentName notificationListener, int userId) {
        ArrayList<MediaController> controllers = new ArrayList<MediaController>();
        try {
            List<IBinder> binders = mService.getSessions(notificationListener, userId);
            int size = binders.size();
            for (int i = 0; i < size; i++) {
                MediaController controller = new MediaController(mContext, ISessionController.Stub
                        .asInterface(binders.get(i)));
                controllers.add(controller);
            }
        } catch (RemoteException e) {
            Log.e(TAG, "Failed to get active sessions: ", e);
        }
        return controllers;
    }

    /**
     * Add a listener to be notified when the list of active sessions
     * changes.This requires the
     * android.Manifest.permission.MEDIA_CONTENT_CONTROL permission be held by
     * the calling app. You may also retrieve this list if your app is an
     * enabled notification listener using the
     * {@link NotificationListenerService} APIs, in which case you must pass the
     * {@link ComponentName} of your enabled listener. Updates will be posted to
     * the thread that registered the listener.
     *
     * @param sessionListener The listener to add.
     * @param notificationListener The enabled notification listener component.
     *            May be null.
     */
    public void addOnActiveSessionsChangedListener(
            @NonNull OnActiveSessionsChangedListener sessionListener,
            @Nullable ComponentName notificationListener) {
        addOnActiveSessionsChangedListener(sessionListener, notificationListener, null);
    }

    /**
     * Add a listener to be notified when the list of active sessions
     * changes.This requires the
     * android.Manifest.permission.MEDIA_CONTENT_CONTROL permission be held by
     * the calling app. You may also retrieve this list if your app is an
     * enabled notification listener using the
     * {@link NotificationListenerService} APIs, in which case you must pass the
     * {@link ComponentName} of your enabled listener. Updates will be posted to
     * the handler specified or to the caller's thread if the handler is null.
     *
     * @param sessionListener The listener to add.
     * @param notificationListener The enabled notification listener component.
     *            May be null.
     * @param handler The handler to post events to.
     */
    public void addOnActiveSessionsChangedListener(
            @NonNull OnActiveSessionsChangedListener sessionListener,
            @Nullable ComponentName notificationListener, @Nullable Handler handler) {
        addOnActiveSessionsChangedListener(sessionListener, notificationListener,
                UserHandle.myUserId(), handler);
    }

    /**
     * Add a listener to be notified when the list of active sessions
     * changes.This requires the
     * android.Manifest.permission.MEDIA_CONTENT_CONTROL permission be held by
     * the calling app. You may also retrieve this list if your app is an
     * enabled notification listener using the
     * {@link NotificationListenerService} APIs, in which case you must pass the
     * {@link ComponentName} of your enabled listener.
     *
     * @param sessionListener The listener to add.
     * @param notificationListener The enabled notification listener component.
     *            May be null.
     * @param userId The userId to listen for changes on.
     * @param handler The handler to post updates on.
     * @hide
     */
    public void addOnActiveSessionsChangedListener(
            @NonNull OnActiveSessionsChangedListener sessionListener,
            @Nullable ComponentName notificationListener, int userId, @Nullable Handler handler) {
        if (sessionListener == null) {
            throw new IllegalArgumentException("listener may not be null");
        }
        if (handler == null) {
            handler = new Handler();
        }
        synchronized (mLock) {
            if (mListeners.get(sessionListener) != null) {
                Log.w(TAG, "Attempted to add session listener twice, ignoring.");
                return;
            }
            SessionsChangedWrapper wrapper = new SessionsChangedWrapper(mContext, sessionListener,
                    handler);
            try {
                mService.addSessionsListener(wrapper.mStub, notificationListener, userId);
                mListeners.put(sessionListener, wrapper);
            } catch (RemoteException e) {
                Log.e(TAG, "Error in addOnActiveSessionsChangedListener.", e);
            }
        }
    }

    /**
     * Stop receiving active sessions updates on the specified listener.
     *
     * @param listener The listener to remove.
     */
    public void removeOnActiveSessionsChangedListener(
            @NonNull OnActiveSessionsChangedListener listener) {
        if (listener == null) {
            throw new IllegalArgumentException("listener may not be null");
        }
        synchronized (mLock) {
            SessionsChangedWrapper wrapper = mListeners.remove(listener);
            if (wrapper != null) {
                try {
                    mService.removeSessionsListener(wrapper.mStub);
                } catch (RemoteException e) {
                    Log.e(TAG, "Error in removeOnActiveSessionsChangedListener.", e);
                } finally {
                    wrapper.release();
                }
            }
        }
    }

    /**
     * Set the remote volume controller to receive volume updates on. Only for
     * use by system UI.
     *
     * @param rvc The volume controller to receive updates on.
     * @hide
     */
    public void setRemoteVolumeController(IRemoteVolumeController rvc) {
        try {
            mService.setRemoteVolumeController(rvc);
        } catch (RemoteException e) {
            Log.e(TAG, "Error in setRemoteVolumeController.", e);
        }
    }

    /**
     * Send a media key event. The receiver will be selected automatically.
     *
     * @param keyEvent The KeyEvent to send.
     * @hide
     */
    public void dispatchMediaKeyEvent(@NonNull KeyEvent keyEvent) {
        dispatchMediaKeyEvent(keyEvent, false);
    }

    /**
     * Send a media key event. The receiver will be selected automatically.
     *
     * @param keyEvent The KeyEvent to send.
     * @param needWakeLock True if a wake lock should be held while sending the key.
     * @hide
     */
    public void dispatchMediaKeyEvent(@NonNull KeyEvent keyEvent, boolean needWakeLock) {
        dispatchMediaKeyEventInternal(false, keyEvent, needWakeLock);
    }

    /**
     * Send a media key event as system component. The receiver will be selected automatically.
     * <p>
     * Should be only called by the {@link com.android.internal.policy.PhoneWindow} or
     * {@link android.view.FallbackEventHandler} when the foreground activity didn't consume the key
     * from the hardware devices.
     *
     * @param keyEvent The KeyEvent to send.
     * @hide
     */
    public void dispatchMediaKeyEventAsSystemService(KeyEvent keyEvent) {
        dispatchMediaKeyEventInternal(true, keyEvent, false);
    }

    private void dispatchMediaKeyEventInternal(boolean asSystemService, @NonNull KeyEvent keyEvent,
            boolean needWakeLock) {
        try {
            mService.dispatchMediaKeyEvent(mContext.getPackageName(), asSystemService, keyEvent,
                    needWakeLock);
        } catch (RemoteException e) {
            Log.e(TAG, "Failed to send key event.", e);
        }
    }

    /**
     * Send a volume key event. The receiver will be selected automatically.
     *
     * @param keyEvent The volume KeyEvent to send.
     * @hide
     */
    public void dispatchVolumeKeyEvent(@NonNull KeyEvent keyEvent, int stream, boolean musicOnly) {
        dispatchVolumeKeyEventInternal(false, keyEvent, stream, musicOnly);
    }

    /**
     * Dispatches the volume button event as system service to the session. This only effects the
     * {@link MediaSession.Callback#getCurrentControllerInfo()} and doesn't bypass any permission
     * check done by the system service.
     * <p>
     * Should be only called by the {@link com.android.internal.policy.PhoneWindow} or
     * {@link android.view.FallbackEventHandler} when the foreground activity didn't consume the key
     * from the hardware devices.
     *
     * @param keyEvent The KeyEvent to send.
     * @hide
     */
    public void dispatchVolumeKeyEventAsSystemService(@NonNull KeyEvent keyEvent, int streamType) {
        dispatchVolumeKeyEventInternal(true, keyEvent, streamType, false);
    }

    private void dispatchVolumeKeyEventInternal(boolean asSystemService, @NonNull KeyEvent keyEvent,
            int stream, boolean musicOnly) {
        try {
            mService.dispatchVolumeKeyEvent(mContext.getPackageName(), asSystemService, keyEvent,
                    stream, musicOnly);
        } catch (RemoteException e) {
            Log.e(TAG, "Failed to send volume key event.", e);
        }
    }

    /**
     * Dispatch an adjust volume request to the system. It will be sent to the
     * most relevant audio stream or media session. The direction must be one of
     * {@link AudioManager#ADJUST_LOWER}, {@link AudioManager#ADJUST_RAISE},
     * {@link AudioManager#ADJUST_SAME}.
     *
     * @param suggestedStream The stream to fall back to if there isn't a
     *            relevant stream
     * @param direction The direction to adjust volume in.
     * @param flags Any flags to include with the volume change.
     * @hide
     */
    public void dispatchAdjustVolume(int suggestedStream, int direction, int flags) {
        try {
            mService.dispatchAdjustVolume(mContext.getPackageName(), suggestedStream, direction,
                    flags);
        } catch (RemoteException e) {
            Log.e(TAG, "Failed to send adjust volume.", e);
        }
    }

    /**
     * Checks whether the remote user is a trusted app.
     * <p>
     * An app is trusted if the app holds the android.Manifest.permission.MEDIA_CONTENT_CONTROL
     * permission or has an enabled notification listener.
     *
     * @param userInfo The remote user info from either
     *            {@link MediaSession#getCurrentControllerInfo()} or
     *            {@link MediaBrowserService#getCurrentBrowserInfo()}.
     * @return {@code true} if the remote user is trusted and its package name matches with the UID.
     *            {@code false} otherwise.
     */
    public boolean isTrustedForMediaControl(@NonNull RemoteUserInfo userInfo) {
        if (userInfo == null) {
            throw new IllegalArgumentException("userInfo may not be null");
        }
        if (userInfo.getPackageName() == null) {
            return false;
        }
        try {
            return mService.isTrusted(
                    userInfo.getPackageName(), userInfo.getPid(), userInfo.getUid());
        } catch (RemoteException e) {
            Log.wtf(TAG, "Cannot communicate with the service.", e);
        }
        return false;
    }

    /**
     * Called when a {@link MediaSession2} is created.
     * @hide
     */
    public boolean createSession2(@NonNull SessionToken2 token) {
        if (token == null) {
            return false;
        }
        try {
            return mService.createSession2(token.toBundle());
        } catch (RemoteException e) {
            Log.wtf(TAG, "Cannot communicate with the service.", e);
        }
        return false;
    }

    /**
     * Called when a {@link MediaSession2} is destroyed.
     * @hide
     */
    public void destroySession2(@NonNull SessionToken2 token) {
        if (token == null) {
            return;
        }
        try {
            mService.destroySession2(token.toBundle());
        } catch (RemoteException e) {
            Log.wtf(TAG, "Cannot communicate with the service.", e);
        }
    }

    /**
     * @hide
     * Get {@link List} of {@link SessionToken2} whose sessions are active now. This list represents
     * active sessions regardless of whether they're {@link MediaSession2} or
     * {@link MediaSessionService2}.
     * <p>
     * This requires the android.Manifest.permission.MEDIA_CONTENT_CONTROL permission be held by the
     * calling app. You may also retrieve this list if your app is an enabled notification listener
     * using the {@link NotificationListenerService} APIs.
     *
     * @return list of tokens
     */
    public List<SessionToken2> getActiveSessionTokens() {
        try {
            List<Bundle> bundles = mService.getSessionTokens(
                    /* activeSessionOnly */ true, /* sessionServiceOnly */ false,
                    mContext.getPackageName());
            return toTokenList(bundles);
        } catch (RemoteException e) {
            Log.wtf(TAG, "Cannot communicate with the service.", e);
            return Collections.emptyList();
        }
    }

    /**
     * @hide
     * Get {@link List} of {@link SessionToken2} for {@link MediaSessionService2} regardless of their
     * activeness. This list represents media apps that support background playback.
     * <p>
     * This requires the android.Manifest.permission.MEDIA_CONTENT_CONTROL permission be held by the
     * calling app. You may also retrieve this list if your app is an enabled notification listener
     * using the {@link NotificationListenerService} APIs.
     *
     * @return list of tokens
     */
    public List<SessionToken2> getSessionServiceTokens() {
        try {
            List<Bundle> bundles = mService.getSessionTokens(
                    /* activeSessionOnly */ false, /* sessionServiceOnly */ true,
                    mContext.getPackageName());
            return toTokenList(bundles);
        } catch (RemoteException e) {
            Log.wtf(TAG, "Cannot communicate with the service.", e);
            return Collections.emptyList();
        }
    }

    /**
     * @hide
     * Get all {@link SessionToken2}s. This is the combined list of {@link #getActiveSessionTokens()}
     * and {@link #getSessionServiceTokens}.
     * <p>
     * This requires the android.Manifest.permission.MEDIA_CONTENT_CONTROL permission be held by the
     * calling app. You may also retrieve this list if your app is an enabled notification listener
     * using the {@link NotificationListenerService} APIs.
     *
     * @return list of tokens
     * @see #getActiveSessionTokens
     * @see #getSessionServiceTokens
     */
    public List<SessionToken2> getAllSessionTokens() {
        try {
            List<Bundle> bundles = mService.getSessionTokens(
                    /* activeSessionOnly */ false, /* sessionServiceOnly */ false,
                    mContext.getPackageName());
            return toTokenList(bundles);
        } catch (RemoteException e) {
            Log.wtf(TAG, "Cannot communicate with the service.", e);
            return Collections.emptyList();
        }
    }

    /**
     * @hide
     * Add a listener to be notified when the {@link #getAllSessionTokens()} changes.
     * <p>
     * This requires the android.Manifest.permission.MEDIA_CONTENT_CONTROL permission be held by the
     * calling app. You may also retrieve this list if your app is an enabled notification listener
     * using the {@link NotificationListenerService} APIs.
     *
     * @param executor executor to run this command
     * @param listener The listener to add.
     */
    public void addOnSessionTokensChangedListener(@NonNull @CallbackExecutor Executor executor,
            @NonNull OnSessionTokensChangedListener listener) {
        addOnSessionTokensChangedListener(UserHandle.myUserId(), executor, listener);
    }

    /**
     * Add a listener to be notified when the {@link #getAllSessionTokens()} changes.
     * <p>
     * This requires the android.Manifest.permission.MEDIA_CONTENT_CONTROL permission be held by the
     * calling app. You may also retrieve this list if your app is an enabled notification listener
     * using the {@link NotificationListenerService} APIs.
     *
     * @param userId The userId to listen for changes on.
     * @param executor executor to run this command
     * @param listener The listener to add.
     * @hide
     */
    public void addOnSessionTokensChangedListener(int userId,
            @NonNull @CallbackExecutor Executor executor,
            @NonNull OnSessionTokensChangedListener listener) {
        if (executor == null) {
            throw new IllegalArgumentException("executor may not be null");
        }
        if (listener == null) {
            throw new IllegalArgumentException("listener may not be null");
        }
        synchronized (mLock) {
            if (mSessionTokensListener.get(listener) != null) {
                Log.w(TAG, "Attempted to add session listener twice, ignoring.");
                return;
            }
            SessionTokensChangedWrapper wrapper = new SessionTokensChangedWrapper(
                    mContext, executor, listener);
            try {
                mService.addSessionTokensListener(wrapper.mStub, userId, mContext.getPackageName());
                mSessionTokensListener.put(listener, wrapper);
            } catch (RemoteException e) {
                Log.e(TAG, "Error in addSessionTokensListener.", e);
            }
        }
    }

    /**
     * @hide
     * Stop receiving session token updates on the specified listener.
     *
     * @param listener The listener to remove.
     */
    public void removeOnSessionTokensChangedListener(
            @NonNull OnSessionTokensChangedListener listener) {
        if (listener == null) {
            throw new IllegalArgumentException("listener may not be null");
        }
        synchronized (mLock) {
            SessionTokensChangedWrapper wrapper = mSessionTokensListener.remove(listener);
            if (wrapper != null) {
                try {
                    mService.removeSessionTokensListener(wrapper.mStub, mContext.getPackageName());
                } catch (RemoteException e) {
                    Log.e(TAG, "Error in removeSessionTokensListener.", e);
                } finally {
                    wrapper.release();
                }
            }
        }
    }

    private static List<SessionToken2> toTokenList(List<Bundle> bundles) {
        List<SessionToken2> tokens = new ArrayList<>();
        if (bundles != null) {
            for (int i = 0; i < bundles.size(); i++) {
                SessionToken2 token = SessionToken2.fromBundle(bundles.get(i));
                if (token != null) {
                    tokens.add(token);
                }
            }
        }
        return tokens;
    }

    /**
     * Check if the global priority session is currently active. This can be
     * used to decide if media keys should be sent to the session or to the app.
     *
     * @hide
     */
    public boolean isGlobalPriorityActive() {
        try {
            return mService.isGlobalPriorityActive();
        } catch (RemoteException e) {
            Log.e(TAG, "Failed to check if the global priority is active.", e);
        }
        return false;
    }

    /**
     * Set the volume key long-press listener. While the listener is set, the listener
     * gets the volume key long-presses instead of changing volume.
     *
     * <p>System can only have a single volume key long-press listener.
     *
     * @param listener The volume key long-press listener. {@code null} to reset.
     * @param handler The handler on which the listener should be invoked, or {@code null}
     *            if the listener should be invoked on the calling thread's looper.
     * @hide
     */
    @SystemApi
    @RequiresPermission(android.Manifest.permission.SET_VOLUME_KEY_LONG_PRESS_LISTENER)
    public void setOnVolumeKeyLongPressListener(
            OnVolumeKeyLongPressListener listener, @Nullable Handler handler) {
        synchronized (mLock) {
            try {
                if (listener == null) {
                    mOnVolumeKeyLongPressListener = null;
                    mService.setOnVolumeKeyLongPressListener(null);
                } else {
                    if (handler == null) {
                        handler = new Handler();
                    }
                    mOnVolumeKeyLongPressListener =
                            new OnVolumeKeyLongPressListenerImpl(listener, handler);
                    mService.setOnVolumeKeyLongPressListener(mOnVolumeKeyLongPressListener);
                }
            } catch (RemoteException e) {
                Log.e(TAG, "Failed to set volume key long press listener", e);
            }
        }
    }

    /**
     * Set the media key listener. While the listener is set, the listener
     * gets the media key before any other media sessions but after the global priority session.
     * If the listener handles the key (i.e. returns {@code true}),
     * other sessions will not get the event.
     *
     * <p>System can only have a single media key listener.
     *
     * @param listener The media key listener. {@code null} to reset.
     * @param handler The handler on which the listener should be invoked, or {@code null}
     *            if the listener should be invoked on the calling thread's looper.
     * @hide
     */
    @SystemApi
    @RequiresPermission(android.Manifest.permission.SET_MEDIA_KEY_LISTENER)
    public void setOnMediaKeyListener(OnMediaKeyListener listener, @Nullable Handler handler) {
        synchronized (mLock) {
            try {
                if (listener == null) {
                    mOnMediaKeyListener = null;
                    mService.setOnMediaKeyListener(null);
                } else {
                    if (handler == null) {
                        handler = new Handler();
                    }
                    mOnMediaKeyListener = new OnMediaKeyListenerImpl(listener, handler);
                    mService.setOnMediaKeyListener(mOnMediaKeyListener);
                }
            } catch (RemoteException e) {
                Log.e(TAG, "Failed to set media key listener", e);
            }
        }
    }

    /**
     * Set a {@link Callback}.
     *
     * <p>System can only have a single callback, and the callback can only be set by
     * Bluetooth service process.
     *
     * @param callback A {@link Callback}. {@code null} to reset.
     * @param handler The handler on which the callback should be invoked, or {@code null}
     *            if the callback should be invoked on the calling thread's looper.
     * @hide
     */
    public void setCallback(@Nullable Callback callback, @Nullable Handler handler) {
        synchronized (mLock) {
            try {
                if (callback == null) {
                    mCallback = null;
                    mService.setCallback(null);
                } else {
                    if (handler == null) {
                        handler = new Handler();
                    }
                    mCallback = new CallbackImpl(callback, handler);
                    mService.setCallback(mCallback);
                }
            } catch (RemoteException e) {
                Log.e(TAG, "Failed to set media key callback", e);
            }
        }
    }

    /**
     * Listens for changes to the list of active sessions. This can be added
     * using {@link #addOnActiveSessionsChangedListener}.
     */
    public interface OnActiveSessionsChangedListener {
        public void onActiveSessionsChanged(@Nullable List<MediaController> controllers);
    }

    /**
     * @hide
     * Listens for changes to the {@link #getAllSessionTokens()}. This can be added
     * using {@link #addOnActiveSessionsChangedListener}.
     */
    public interface OnSessionTokensChangedListener {
        void onSessionTokensChanged(@NonNull List<SessionToken2> tokens);
    }

    /**
     * Listens the volume key long-presses.
     * @hide
     */
    @SystemApi
    public interface OnVolumeKeyLongPressListener {
        /**
         * Called when the volume key is long-pressed.
         * <p>This will be called for both down and up events.
         */
        void onVolumeKeyLongPress(KeyEvent event);
    }

    /**
     * Listens the media key.
     * @hide
     */
    @SystemApi
    public interface OnMediaKeyListener {
        /**
         * Called when the media key is pressed.
         * <p>If the listener consumes the initial down event (i.e. ACTION_DOWN with
         * repeat count zero), it must also comsume all following key events.
         * (i.e. ACTION_DOWN with repeat count more than zero, and ACTION_UP).
         * <p>If it takes more than 1s to return, the key event will be sent to
         * other media sessions.
         */
        boolean onMediaKey(KeyEvent event);
    }

    /**
     * Callbacks for the media session service.
     *
     * <p>Called when a media key event is dispatched or the addressed player is changed.
     * The addressed player is either the media session or the media button receiver that will
     * receive media key events.
     * @hide
     */
    public static abstract class Callback {
        /**
         * Called when a media key event is dispatched to the media session
         * through the media session service.
         *
         * @param event Dispatched media key event.
         * @param sessionToken The media session's token.
         */
        public abstract void onMediaKeyEventDispatched(KeyEvent event,
                MediaSession.Token sessionToken);

        /**
         * Called when a media key event is dispatched to the media button receiver
         * through the media session service.
         * <p>MediaSessionService may broadcast key events to the media button receiver
         * when reviving playback after the media session is released.
         *
         * @param event Dispatched media key event.
         * @param mediaButtonReceiver The media button receiver.
         */
        public abstract void onMediaKeyEventDispatched(KeyEvent event,
                ComponentName mediaButtonReceiver);

        /**
         * Called when the addressed player is changed to a media session.
         * <p>One of the {@ #onAddressedPlayerChanged} will be also called immediately after
         * {@link #setCallback} if the addressed player exists.
         *
         * @param sessionToken The media session's token.
         */
        public abstract void onAddressedPlayerChanged(MediaSession.Token sessionToken);

        /**
         * Called when the addressed player is changed to the media button receiver.
         * <p>One of the {@ #onAddressedPlayerChanged} will be also called immediately after
         * {@link #setCallback} if the addressed player exists.
         *
         * @param mediaButtonReceiver The media button receiver.
         */
        public abstract void onAddressedPlayerChanged(ComponentName mediaButtonReceiver);
    }

    /**
     * Information of a remote user of {@link MediaSession} or {@link MediaBrowserService}.
     * This can be used to decide whether the remote user is trusted app, and also differentiate
     * caller of {@link MediaSession} and {@link MediaBrowserService} callbacks.
     * <p>
     * See {@link #equals(Object)} to take a look at how it differentiate media controller.
     *
     * @see #isTrustedForMediaControl(RemoteUserInfo)
     */
    public static final class RemoteUserInfo {
        private final String mPackageName;
        private final int mPid;
        private final int mUid;
        private final IBinder mCallerBinder;

        public RemoteUserInfo(@NonNull String packageName, int pid, int uid) {
            this(packageName, pid, uid, null);
        }

        /**
         * @hide
         */
        public RemoteUserInfo(String packageName, int pid, int uid, IBinder callerBinder) {
            mPackageName = packageName;
            mPid = pid;
            mUid = uid;
            mCallerBinder = callerBinder;
        }

        /**
         * @return package name of the controller
         */
        public String getPackageName() {
            return mPackageName;
        }

        /**
         * @return pid of the controller
         */
        public int getPid() {
            return mPid;
        }

        /**
         * @return uid of the controller
         */
        public int getUid() {
            return mUid;
        }

        /**
         * Returns equality of two RemoteUserInfo. Two RemoteUserInfos are the same only if they're
         * sent to the same controller (either {@link MediaController} or
         * {@link MediaBrowser}. If it's not nor one of them is triggered by the key presses, they
         * would be considered as different one.
         * <p>
         * If you only want to compare the caller's package, compare them with the
         * {@link #getPackageName()}, {@link #getPid()}, and/or {@link #getUid()} directly.
         *
         * @param obj the reference object with which to compare.
         * @return {@code true} if equals, {@code false} otherwise
         */
        @Override
        public boolean equals(Object obj) {
            if (!(obj instanceof RemoteUserInfo)) {
                return false;
            }
            if (this == obj) {
                return true;
            }
            RemoteUserInfo otherUserInfo = (RemoteUserInfo) obj;
            return (mCallerBinder == null || otherUserInfo.mCallerBinder == null) ? false
                    : mCallerBinder.equals(otherUserInfo.mCallerBinder);
        }

        @Override
        public int hashCode() {
            return Objects.hash(mPackageName, mPid, mUid);
        }
    }

    private static final class SessionsChangedWrapper {
        private Context mContext;
        private OnActiveSessionsChangedListener mListener;
        private Handler mHandler;

        public SessionsChangedWrapper(Context context, OnActiveSessionsChangedListener listener,
                Handler handler) {
            mContext = context;
            mListener = listener;
            mHandler = handler;
        }

        private final IActiveSessionsListener.Stub mStub = new IActiveSessionsListener.Stub() {
            @Override
            public void onActiveSessionsChanged(final List<MediaSession.Token> tokens) {
                final Handler handler = mHandler;
                if (handler != null) {
                    handler.post(new Runnable() {
                        @Override
                        public void run() {
                            final Context context = mContext;
                            if (context != null) {
                                ArrayList<MediaController> controllers = new ArrayList<>();
                                int size = tokens.size();
                                for (int i = 0; i < size; i++) {
                                    controllers.add(new MediaController(context, tokens.get(i)));
                                }
                                final OnActiveSessionsChangedListener listener = mListener;
                                if (listener != null) {
                                    listener.onActiveSessionsChanged(controllers);
                                }
                            }
                        }
                    });
                }
            }
        };

        private void release() {
            mListener = null;
            mContext = null;
            mHandler = null;
        }
    }

    private static final class SessionTokensChangedWrapper {
        private Context mContext;
        private Executor mExecutor;
        private OnSessionTokensChangedListener mListener;

        public SessionTokensChangedWrapper(Context context, Executor executor,
                OnSessionTokensChangedListener listener) {
            mContext = context;
            mExecutor = executor;
            mListener = listener;
        }

        private final ISessionTokensListener.Stub mStub = new ISessionTokensListener.Stub() {
            @Override
            public void onSessionTokensChanged(final List<Bundle> bundles) {
                final Executor executor = mExecutor;
                if (executor != null) {
                    executor.execute(() -> {
                        final Context context = mContext;
                        final OnSessionTokensChangedListener listener = mListener;
                        if (context != null && listener != null) {
                            listener.onSessionTokensChanged(toTokenList(bundles));
                        }
                    });
                }
            }
        };

        private void release() {
            mListener = null;
            mContext = null;
            mExecutor = null;
        }
    }

    private static final class OnVolumeKeyLongPressListenerImpl
            extends IOnVolumeKeyLongPressListener.Stub {
        private OnVolumeKeyLongPressListener mListener;
        private Handler mHandler;

        public OnVolumeKeyLongPressListenerImpl(
                OnVolumeKeyLongPressListener listener, Handler handler) {
            mListener = listener;
            mHandler = handler;
        }

        @Override
        public void onVolumeKeyLongPress(KeyEvent event) {
            if (mListener == null || mHandler == null) {
                Log.w(TAG, "Failed to call volume key long-press listener." +
                        " Either mListener or mHandler is null");
                return;
            }
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    mListener.onVolumeKeyLongPress(event);
                }
            });
        }
    }

    private static final class OnMediaKeyListenerImpl extends IOnMediaKeyListener.Stub {
        private OnMediaKeyListener mListener;
        private Handler mHandler;

        public OnMediaKeyListenerImpl(OnMediaKeyListener listener, Handler handler) {
            mListener = listener;
            mHandler = handler;
        }

        @Override
        public void onMediaKey(KeyEvent event, ResultReceiver result) {
            if (mListener == null || mHandler == null) {
                Log.w(TAG, "Failed to call media key listener." +
                        " Either mListener or mHandler is null");
                return;
            }
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    boolean handled = mListener.onMediaKey(event);
                    Log.d(TAG, "The media key listener is returned " + handled);
                    if (result != null) {
                        result.send(
                                handled ? RESULT_MEDIA_KEY_HANDLED : RESULT_MEDIA_KEY_NOT_HANDLED,
                                null);
                    }
                }
            });
        }
    }

    private static final class CallbackImpl extends ICallback.Stub {
        private final Callback mCallback;
        private final Handler mHandler;

        public CallbackImpl(@NonNull Callback callback, @NonNull Handler handler) {
            mCallback = callback;
            mHandler = handler;
        }

        @Override
        public void onMediaKeyEventDispatchedToMediaSession(KeyEvent event,
                MediaSession.Token sessionToken) {
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    mCallback.onMediaKeyEventDispatched(event, sessionToken);
                }
            });
        }

        @Override
        public void onMediaKeyEventDispatchedToMediaButtonReceiver(KeyEvent event,
                ComponentName mediaButtonReceiver) {
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    mCallback.onMediaKeyEventDispatched(event, mediaButtonReceiver);
                }
            });
        }

        @Override
        public void onAddressedPlayerChangedToMediaSession(MediaSession.Token sessionToken) {
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    mCallback.onAddressedPlayerChanged(sessionToken);
                }
            });
        }

        @Override
        public void onAddressedPlayerChangedToMediaButtonReceiver(
                ComponentName mediaButtonReceiver) {
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    mCallback.onAddressedPlayerChanged(mediaButtonReceiver);
                }
            });
        }
    }
}