Android example source code file (NotificationPlayer.java)

This example Android source code file (NotificationPlayer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, audiomanager, cmdthread, command, creationandcompletionthread, exception, linkedlist, media, mediaplayer, notificationplayer, object, oncompletionlistener, os, photo, play, sound, stop, string, uri, video

The NotificationPlayer.java Android example source code

/*
 * Copyright (C) 2008 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 com.android.server;

import android.content.Context;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.net.Uri;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.os.PowerManager;
import android.os.SystemClock;
import android.util.Log;

import java.io.IOException;
import java.lang.IllegalStateException;
import java.lang.Thread;
import java.util.LinkedList;

/**
 * @hide
 * This class is provides the same interface and functionality as android.media.AsyncPlayer
 * with the following differences: 
 * - whenever audio is played, audio focus is requested,
 * - whenever audio playback is stopped or the playback completed, audio focus is abandoned.
 */
public class NotificationPlayer implements OnCompletionListener {
    private static final int PLAY = 1;
    private static final int STOP = 2;
    private static final boolean mDebug = false;

    private static final class Command {
        int code;
        Context context;
        Uri uri;
        boolean looping;
        int stream;
        long requestTime;

        public String toString() {
            return "{ code=" + code + " looping=" + looping + " stream=" + stream
                    + " uri=" + uri + " }";
        }
    }

    private LinkedList<Command> mCmdQueue = new LinkedList();

    private Looper mLooper;

    /*
     * Besides the use of audio focus, the only implementation difference between AsyncPlayer and
     * NotificationPlayer resides in the creation of the MediaPlayer. For the completion callback,
     * OnCompletionListener, to be called at the end of the playback, the MediaPlayer needs to
     * be created with a looper running so its event handler is not null.
     */
    private final class CreationAndCompletionThread extends Thread {
        public Command mCmd;
        public CreationAndCompletionThread(Command cmd) {
            super();
            mCmd = cmd;
        }

        public void run() {
            Looper.prepare();
            mLooper = Looper.myLooper();
            synchronized(this) {
                AudioManager audioManager =
                    (AudioManager) mCmd.context.getSystemService(Context.AUDIO_SERVICE);
                try {
                    MediaPlayer player = new MediaPlayer();
                    player.setAudioStreamType(mCmd.stream);
                    player.setDataSource(mCmd.context, mCmd.uri);
                    player.setLooping(mCmd.looping);
                    player.prepare();
                    if ((mCmd.uri != null) && (mCmd.uri.getEncodedPath() != null)
                            && (mCmd.uri.getEncodedPath().length() > 0)) {
                        if (mCmd.looping) {
                            audioManager.requestAudioFocus(null, mCmd.stream,
                                    AudioManager.AUDIOFOCUS_GAIN);
                        } else {
                            audioManager.requestAudioFocus(null, mCmd.stream,
                                    AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK);
                        }
                    }
                    player.setOnCompletionListener(NotificationPlayer.this);
                    player.start();
                    if (mPlayer != null) {
                        mPlayer.release();
                    }
                    mPlayer = player;
                }
                catch (Exception e) {
                    Log.w(mTag, "error loading sound for " + mCmd.uri, e);
                }
                mAudioManager = audioManager;
                this.notify();
            }
            Looper.loop();
        }
    };

    private void startSound(Command cmd) {
        // Preparing can be slow, so if there is something else
        // is playing, let it continue until we're done, so there
        // is less of a glitch.
        try {
            if (mDebug) Log.d(mTag, "Starting playback");
            //-----------------------------------
            // This is were we deviate from the AsyncPlayer implementation and create the
            // MediaPlayer in a new thread with which we're synchronized
            synchronized(mCompletionHandlingLock) {
                // if another sound was already playing, it doesn't matter we won't get notified
                // of the completion, since only the completion notification of the last sound
                // matters
                if((mLooper != null)
                        && (mLooper.getThread().getState() != Thread.State.TERMINATED)) {
                    mLooper.quit();
                }
                mCompletionThread = new CreationAndCompletionThread(cmd);
                synchronized(mCompletionThread) {
                    mCompletionThread.start();
                    mCompletionThread.wait();
                }
            }
            //-----------------------------------

            long delay = SystemClock.uptimeMillis() - cmd.requestTime;
            if (delay > 1000) {
                Log.w(mTag, "Notification sound delayed by " + delay + "msecs");
            }
        }
        catch (Exception e) {
            Log.w(mTag, "error loading sound for " + cmd.uri, e);
        }
    }

    private final class CmdThread extends java.lang.Thread {
        CmdThread() {
            super("NotificationPlayer-" + mTag);
        }

        public void run() {
            while (true) {
                Command cmd = null;

                synchronized (mCmdQueue) {
                    if (mDebug) Log.d(mTag, "RemoveFirst");
                    cmd = mCmdQueue.removeFirst();
                }

                switch (cmd.code) {
                case PLAY:
                    if (mDebug) Log.d(mTag, "PLAY");
                    startSound(cmd);
                    break;
                case STOP:
                    if (mDebug) Log.d(mTag, "STOP");
                    if (mPlayer != null) {
                        long delay = SystemClock.uptimeMillis() - cmd.requestTime;
                        if (delay > 1000) {
                            Log.w(mTag, "Notification stop delayed by " + delay + "msecs");
                        }
                        mPlayer.stop();
                        mPlayer.release();
                        mPlayer = null;
                        mAudioManager.abandonAudioFocus(null);
                        mAudioManager = null;
                        if((mLooper != null)
                                && (mLooper.getThread().getState() != Thread.State.TERMINATED)) {
                            mLooper.quit();
                        }
                    } else {
                        Log.w(mTag, "STOP command without a player");
                    }
                    break;
                }

                synchronized (mCmdQueue) {
                    if (mCmdQueue.size() == 0) {
                        // nothing left to do, quit
                        // doing this check after we're done prevents the case where they
                        // added it during the operation from spawning two threads and
                        // trying to do them in parallel.
                        mThread = null;
                        releaseWakeLock();
                        return;
                    }
                }
            }
        }
    }

    public void onCompletion(MediaPlayer mp) {
        if (mAudioManager != null) {
            mAudioManager.abandonAudioFocus(null);
        }
        // if there are no more sounds to play, end the Looper to listen for media completion
        synchronized (mCmdQueue) {
            if (mCmdQueue.size() == 0) {
                synchronized(mCompletionHandlingLock) {
                    if(mLooper != null) {
                        mLooper.quit();
                    }
                    mCompletionThread = null;
                }
            }
        }
    }

    private String mTag;
    private CmdThread mThread;
    private CreationAndCompletionThread mCompletionThread;
    private final Object mCompletionHandlingLock = new Object();
    private MediaPlayer mPlayer;
    private PowerManager.WakeLock mWakeLock;
    private AudioManager mAudioManager;

    // The current state according to the caller.  Reality lags behind
    // because of the asynchronous nature of this class.
    private int mState = STOP;

    /**
     * Construct a NotificationPlayer object.
     *
     * @param tag a string to use for debugging
     */
    public NotificationPlayer(String tag) {
        if (tag != null) {
            mTag = tag;
        } else {
            mTag = "NotificationPlayer";
        }
    }

    /**
     * Start playing the sound.  It will actually start playing at some
     * point in the future.  There are no guarantees about latency here.
     * Calling this before another audio file is done playing will stop
     * that one and start the new one.
     *
     * @param context Your application's context.
     * @param uri The URI to play.  (see {@link MediaPlayer#setDataSource(Context, Uri)})
     * @param looping Whether the audio should loop forever.
     *          (see {@link MediaPlayer#setLooping(boolean)})
     * @param stream the AudioStream to use.
     *          (see {@link MediaPlayer#setAudioStreamType(int)})
     */
    public void play(Context context, Uri uri, boolean looping, int stream) {
        Command cmd = new Command();
        cmd.requestTime = SystemClock.uptimeMillis();
        cmd.code = PLAY;
        cmd.context = context;
        cmd.uri = uri;
        cmd.looping = looping;
        cmd.stream = stream;
        synchronized (mCmdQueue) {
            enqueueLocked(cmd);
            mState = PLAY;
        }
    }

    /**
     * Stop a previously played sound.  It can't be played again or unpaused
     * at this point.  Calling this multiple times has no ill effects.
     */
    public void stop() {
        synchronized (mCmdQueue) {
            // This check allows stop to be called multiple times without starting
            // a thread that ends up doing nothing.
            if (mState != STOP) {
                Command cmd = new Command();
                cmd.requestTime = SystemClock.uptimeMillis();
                cmd.code = STOP;
                enqueueLocked(cmd);
                mState = STOP;
            }
        }
    }

    private void enqueueLocked(Command cmd) {
        mCmdQueue.add(cmd);
        if (mThread == null) {
            acquireWakeLock();
            mThread = new CmdThread();
            mThread.start();
        }
    }

    /**
     * We want to hold a wake lock while we do the prepare and play.  The stop probably is
     * optional, but it won't hurt to have it too.  The problem is that if you start a sound
     * while you're holding a wake lock (e.g. an alarm starting a notification), you want the
     * sound to play, but if the CPU turns off before mThread gets to work, it won't.  The
     * simplest way to deal with this is to make it so there is a wake lock held while the
     * thread is starting or running.  You're going to need the WAKE_LOCK permission if you're
     * going to call this.
     *
     * This must be called before the first time play is called.
     *
     * @hide
     */
    public void setUsesWakeLock(Context context) {
        if (mWakeLock != null || mThread != null) {
            // if either of these has happened, we've already played something.
            // and our releases will be out of sync.
            throw new RuntimeException("assertion failed mWakeLock=" + mWakeLock
                    + " mThread=" + mThread);
        }
        PowerManager pm = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
        mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, mTag);
    }

    private void acquireWakeLock() {
        if (mWakeLock != null) {
            mWakeLock.acquire();
        }
    }

    private void releaseWakeLock() {
        if (mWakeLock != null) {
            mWakeLock.release();
        }
    }
}