Android平台中关于音频播放有以下两种方式:
1. SoundPool —— 适合短促且对反应速度比较高的情况(游戏音效或按键声等)
2. MediaPlayer —— 适合比较长且对时间要求不高的情况
-------------------------------------------------------------------------------------------
SoundPool
1. 创建一个SoundPool
public SoundPool(int maxStream, int streamType, int srcQuality)
maxStream —— 同时播放的流的最大数量
streamType —— 流的类型,一般为STREAM_MUSIC(具体在AudioManager类中列出)
srcQuality —— 采样率转化质量,当前无效果,使用0作为默认值
eg.
SoundPool soundPool = new SoundPool(3, AudioManager.STREAM_MUSIC, 0);
创建了一个最多支持3个流同时播放的,类型标记为音乐的SoundPool。
2. 加载音频资源
可以通过四种途径来记载一个音频资源:
int load(AssetFileDescriptor afd, int priority)
通过一个AssetFileDescriptor对象
int load(Context context, int resId, int priority)
通过一个资源ID
int load(String path, int priority)
通过指定的路径加载
int load(FileDescriptor fd, long offset, long length, int priority)
通过FileDescriptor加载
*API中指出,其中的priority参数目前没有效果,建议设置为1。
一个SoundPool能同时管理多个音频,所以可以通过多次调用load函数来记载,如果记载成功将返回一个非0的soundID ,用于播放时指定特定的音频。
eg.
int soundID1 = soundPool.load(this, R.raw.sound1, 1);
if(soundID1 ==0){
// 记载失败
}else{
// 加载成功
}
int soundID2 = soundPool.load(this, R.raw.sound2, 1);
...
这里加载了两个流,并分别记录了返回的soundID 。
需要注意的是,
流的加载过程是一个将音频解压为原始16位PCM数据的过程,由一个后台线程来进行处理异步,所以初始化后不能立即播放,需要等待一点时间。
3. 播放控制
有以下几个函数可用于控制播放:
final int play(int soundID, float leftVolume, float rightVolume, int priority, int loop, float rate)
播放指定音频的音效,并返回一个streamID 。
priority —— 流的优先级,值越大优先级高,影响当同时播放数量超出了最大支持数时SoundPool对该流的处理;
loop —— 循环播放的次数,0为值播放一次,-1为无限循环,其他值为播放loop+1次(例如,3为一共播放4次).
rate —— 播放的速率,范围0.5-2.0(0.5为一半速率,1.0为正常速率,2.0为两倍速率)
final void pause(int streamID)
暂停指定播放流的音效(streamID 应通过play()返回)。
final void resume(int streamID)
继续播放指定播放流的音效(streamID 应通过play()返回)。
final void stop(int streamID)
终止指定播放流的音效(streamID 应通过play()返回)。
这里需要注意的是,
1.play()函数传递的是一个load()返回的soundID——指向一个被记载的音频资源 ,如果播放成功则返回一个非0的streamID——指向一个成功播放的流 ;同一个soundID 可以通过多次调用play()而获得多个不同的streamID (只要不超出同时播放的最大数量);
2.pause()、resume()和stop()是针对播放流操作的,传递的是play()返回的streamID ;
3.play()中的priority参数,只在同时播放的流的数量超过了预先设定的最大数量是起作用,管理器将自动终止优先级低的播放流。如果存在多个同样优先级的流,再进一步根据其创建事件来处理,新创建的流的年龄是最小的,将被终止;
4.无论如何,程序退出时,手动终止播放并释放资源是必要的。
eg.
//这里对soundID1的音效进行播放——优先级为0(最低),无限循环,正常速率。
int streamID = soundPool.play(soundID1 , 1.0, 1.0, 0, -1, 1.0);
if(streamID ==0){
// 播放失败
}else{
// 播放成功
}
...
// 暂停soundID1的播放
soundPool.pause(streamID );
...
// 恢复soundID1的播放
soundPool.resume(streamID );
...
// 终止播放,记住循环为-1时必须手动停止
soundPool.stop(streamID );
*API中指出,即使使用无效的soundID /streamID (操作失败或指向无效的资源)来调用相关函数也不会导致错误,这样能减轻逻辑的处理。
4. 更多属性设置
其实就是paly()中的一些参数的独立设置:
final void setLoop(int streamID, int loop)
设置指定播放流的循环.
final void setVolume(int streamID, float leftVolume, float rightVolume)
设置指定播放流的音量.
final void setPriority(int streamID, int priority)
设置指定播放流的优先级,上面已说明priority的作用.
final void setRate(int streamID, float rate)
设置指定播放流的速率,0.5-2.0.
5. 释放资源
可操作的函数有:
final boolean unload(int soundID)
卸载一个指定的音频资源.
final void release()
释放SoundPool中的所有音频资源.
-汇总-
一个SoundPool可以:
1.管理多个音频资源,通过load()函数,成功则返回非0的soundID;
2.同时播放多个音频,通过play()函数,成功则返回非0的streamID;
3.pause()、resume()和stop()等操作是针对streamID(播放流)的;
4.当设置为无限循环时,需要手动调用stop()来终止播放;
5.播放流的优先级(play()中的priority参数),只在同时播放数超过设定的最大数时起作用;
6.程序中不用考虑(play触发的)播放流的生命周期,无效的soundID/streamID不会导致程序错误。
-------------------------------------------------------------------------------------------
MediaPlayer
你可以通过new或便捷的静态create函数组来创建一个MediaPlayer对象。
两种方式的比较:
new MediaPlayer()
1.成功调用后,MediaPlayer将处于Idle状态;
2.setDataSource提供了对String(path)、Uri和FileDescriptor格式的资源路径的支持;
3.后续需要手动调用prepare()才能进行播放。
MediaPlayer.create(...)
1.成功调用后,MediaPlayer将处于Prepared状态;
2.create提供了对int(resID)和Uri格式的资源路径的支持;
3.无需(也不能)再次调用prepare()就能直接播放。
MediaPlayer的状态图:
椭圆 代表一个MediaPlayer可能处于的状态。
圆弧 代表(驱动对象状态转变的)播放控制的操作。
>>箭头有两种形态:
单箭 头代表同步函数的调用;
双箭 头代表异步的函数调用。
函数在不同状态下的有效性:
Method Name | Valid Sates | Invalid States | Comments |
attachAuxEffect | {Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Idle, Error} | This method must be called after setDataSource. Calling it does not change the object state. |
getAudioSessionId | any | {} | This method can be called in any state and calling it does not change the object state. |
getCurrentPosition | {Idle, Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
getDuration | {Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Idle, Initialized, Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
getVideoHeight | {Idle, Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
getVideoWidth | {Idle, Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
isPlaying | {Idle, Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
pause | {Started, Paused} | {Idle, Initialized, Prepared, Stopped, PlaybackCompleted, Error} | Successful invoke of this method in a valid state transfers the object to the Paused state. Calling this method in an invalid state transfers the object to theError state. |
prepare | {Initialized, Stopped} | {Idle, Prepared, Started, Paused, PlaybackCompleted, Error} | Successful invoke of this method in a valid state transfers the object to the Prepared state. Calling this method in an invalid state throws an IllegalStateException. |
prepareAsync | {Initialized, Stopped} | {Idle, Prepared, Started, Paused, PlaybackCompleted, Error} | Successful invoke of this method in a valid state transfers the object to the Preparing state. Calling this method in an invalid state throws an IllegalStateException. |
release | any | {} | After release() , the object is no longer available. |
reset | {Idle, Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted, Error} | {} | After reset() , the object is like being just created. |
seekTo | {Prepared, Started, Paused, PlaybackCompleted} | {Idle, Initialized, Stopped, Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
setAudioSessionId | {Idle} | {Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted, Error} | This method must be called in idle state as the audio session ID must be known before calling setDataSource. Calling it does not change the object state. |
setAudioStreamType | {Idle, Initialized, Stopped, Prepared, Started, Paused, PlaybackCompleted} | {Error} | Successful invoke of this method does not change the state. In order for the target audio stream type to become effective, this method must be called before prepare() or prepareAsync(). |
setAuxEffectSendLevel | any | {} | Calling this method does not change the object state. |
setDataSource | {Idle} | {Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted, Error} | Successful invoke of this method in a valid state transfers the object to the Initialized state. Calling this method in an invalid state throws an IllegalStateException. |
setDisplay | any | {} | This method can be called in any state and calling it does not change the object state. |
setLooping | {Idle, Initialized, Stopped, Prepared, Started, Paused, PlaybackCompleted} | {Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
isLooping | any | {} | This method can be called in any state and calling it does not change the object state. |
setOnBufferingUpdateListener | any | {} | This method can be called in any state and calling it does not change the object state. |
setOnCompletionListener | any | {} | This method can be called in any state and calling it does not change the object state. |
setOnErrorListener | any | {} | This method can be called in any state and calling it does not change the object state. |
setOnPreparedListener | any | {} | This method can be called in any state and calling it does not change the object state. |
setOnSeekCompleteListener | any | {} | This method can be called in any state and calling it does not change the object state. |
setScreenOnWhilePlaying | any | {} | This method can be called in any state and calling it does not change the object state. |
setVolume | {Idle, Initialized, Stopped, Prepared, Started, Paused, PlaybackCompleted} | {Error} | Successful invoke of this method does not change the state. |
setWakeMode | any | {} | This method can be called in any state and calling it does not change the object state. |
start | {Prepared, Started, Paused, PlaybackCompleted} | {Idle, Initialized, Stopped, Error} | Successful invoke of this method in a valid state transfers the object to the Started state. Calling this method in an invalid state transfers the object to theError state. |
stop | {Prepared, Started, Stopped, Paused, PlaybackCompleted} | {Idle, Initialized, Error} | Successful invoke of this method in a valid state transfers the object to the Stopped state. Calling this method in an invalid state transfers the object to theError state. |
要点:
1.如果由于错误的操作(参照上图)导致MediaPlayer处于Error状态,可通过reset()函数来使其恢复到Idle状态,再重新执行setDataSource等初始化操作(ps:如果是通过create函数绑定资源ID创建的就郁闷了...);
2.API中指出虽然reset后的MediaPlayer就像相当于新new的一样,但存在微妙的差异的:
在这两种情况下播放器处于Idle状态,此时调用getCurrentPosition(), getDuration(),getVideoHeight(),getVideoWidth(), setAudioStreamType(int),setLooping(boolean), setVolume(float, float), pause(), start(), stop(),seekTo(int), prepare() 或 prepareAsync() 等函数都属与编程错误。当在MediaPlayer刚创建后调用这些函数,用户指定的OnErrorListener.onError() 回调函数不会被internal player engine(内部播放引擎)调用,并且播放器的状态依然未变;但如果是在调用reset() 函数之后,用户指定的OnErrorListener.onError() 回调函数将会被internal player engine(内部播放引擎)调用,并且播放器的状态将转变为Error(错误)状态。
3.使用完毕后应该立即调用release()函数来释放资源,如果操作成功,MediaPlayer对象将处于End状态,此时无法再进行任何操作,除非重新创建MediaPlayer对象。
更多的细节通过一个用new方式来创建的示例说明:
// 通过new创建后的player处于Idle状态 MediaPlayer mp = new MediaPlayer(); if(mp==null){ // new创建有可能会返回null值,检测是好的习惯 return; } // 设置资源路径,成功执行的话player将处于Initialized状态 try { mp.setDataSource("/sdcard/test.mp3"); // 直接传URL也是可以的,将自动处理缓冲 } catch (IllegalArgumentException e) { e.printStackTrace(); } catch (IllegalStateException e) { // 如果在非Idle状态下调用setDataSource就会导致该异常 e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } // 设置必要的监听器 mp.setOnPreparedListener(new OnPreparedListener(){ @Override public void onPrepared(MediaPlayer mp) { // 这时能确保player处于Prepared状态,触发start是最合适的 mp.start(); } }); mp.setOnCompletionListener(new OnCompletionListener() { @Override public void onCompletion(MediaPlayer mp) { // 正常播放结束,可以触发播放下一首 } }); mp.setOnErrorListener(new OnErrorListener() { @Override public boolean onError(MediaPlayer mp, int what, intextra) { // 操作错误或其他原因导致的错误会在这里被通知 return true; } }); // 连接并加载资源 try { mp.prepare(); // mp.prepareAsync() 这也是可以的,这是异步处理,上面的是同步处理,实际加载完毕以OnPreparedListener.onPrepared()为准。 } catch (IllegalStateException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } // mp.start(); // 建议在OnPreparedListener.onPrepared()回调中触发该函数,特别是使用异步加载时 /** * ... 你的其他操作 ... */ // 终止播放并释放资源 try{ mp.stop(); // 这是必要的,如果你设置了循环播放,否则程序退出了音乐仍在后台继续播... mp.release(); }catch(IllegalStateException e){ e.printStackTrace(); }
播放控制上基本与SoundPool相同有:
start()、pause()、stop()、seekTo()、setLooping()...
需要注意的是, 循环播放设置上与SoundPool不同,不能指定确定的循环次数,而是一个布尔值,指定是否循环播放...
更多的函数使用请查阅API文档。