/*
* 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 android.media;
import android.content.Context;
import android.net.Uri;
import android.os.PowerManager;
import android.util.Log;
import java.io.IOException;
import java.lang.IllegalStateException;
/**
* Plays a series of audio URIs, but does all the hard work on another thread
* so that any slowness with preparing or loading doesn't block the calling thread.
*/
public class AsyncPlayer {
private static final int PLAY = 1;
private static final int STOP = 2;
private static final class Command {
Command next;
int code;
Context context;
Uri uri;
boolean looping;
int stream;
public String toString() {
return "{ code=" + code + " looping=" + looping + " stream=" + stream
+ " uri=" + uri + " }";
}
}
private final class Thread extends java.lang.Thread {
Thread() {
super("AsyncPlayer-" + mTag);
}
public void run() {
while (true) {
Command cmd = null;
synchronized (mLock) {
if (mHead != null) {
cmd = mHead;
mHead = cmd.next;
if (mTail == cmd) {
mTail = null;
}
}
}
switch (cmd.code) {
case PLAY:
try {
// 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.
MediaPlayer player = new MediaPlayer();
player.setAudioStreamType(cmd.stream);
player.setDataSource(cmd.context, cmd.uri);
player.setLooping(cmd.looping);
player.prepare();
player.start();
if (mPlayer != null) {
mPlayer.release();
}
mPlayer = player;
}
catch (IOException e) {
Log.w(mTag, "error loading sound for " + cmd.uri, e);
} catch (IllegalStateException e) {
Log.w(mTag, "IllegalStateException (content provider died?) " + cmd.uri, e);
}
break;
case STOP:
if (mPlayer != null) {
mPlayer.stop();
mPlayer.release();
mPlayer = null;
} else {
Log.w(mTag, "STOP command without a player");
}
break;
}
synchronized (mLock) {
if (mHead == null) {
// 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;
}
}
}
}
}
private String mTag;
private Command mHead;
private Command mTail;
private Thread mThread;
private MediaPlayer mPlayer;
private Object mLock = new Object();
private PowerManager.WakeLock mWakeLock;
// The current state according to the caller. Reality lags behind
// because of the asynchronous nature of this class.
private int mState = STOP;
/**
* Construct an AsyncPlayer object.
*
* @param tag a string to use for debugging
*/
public AsyncPlayer(String tag) {
if (tag != null) {
mTag = tag;
} else {
mTag = "AsyncPlayer";
}
}
/**
* 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.code = PLAY;
cmd.context = context;
cmd.uri = uri;
cmd.looping = looping;
cmd.stream = stream;
synchronized (mLock) {
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 (mLock) {
// 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.code = STOP;
enqueueLocked(cmd);
mState = STOP;
}
}
}
private void enqueueLocked(Command cmd) {
if (mTail == null) {
mHead = cmd;
} else {
mTail.next = cmd;
}
mTail = cmd;
if (mThread == null) {
acquireWakeLock();
mThread = new Thread();
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();
}
}
}
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