AudioManager获取、释放媒体焦点

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我是靠谱客的博主懵懂台灯，最近开发中收集的这篇文章主要介绍AudioManager获取、释放媒体焦点，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

转载自：http://blog.csdn.net/chenchuntong/article/details/8813719

平时开发的时候遇到这样的一个问题: 我开着系统的音乐播放器，我在我的应用程序里面播一段音乐两个音乐会同时播放通过在stackoverflow查资料后才发行我们得自己音乐需要获取焦点，在我们音乐播完了以后释放掉焦点。这样系统的歌曲会继续播放下面介绍一下步骤

1.获取AudioManager对象

AudioManager am = (AudioManager) getSystemService(Context.AUDIO_SERVICE);

2. 注册OnAudioFocusChangeListener监听

OnAudioFocusChangeListener afChangeListener = new OnAudioFocusChangeListener() {
  public void onAudioFocusChange(int focusChange) {
   if (focusChange == AudioManager.AUDIOFOCUS_LOSS_TRANSIENT) {
    if(mediaPlayer.isPlaying()){
     mediaPlayer.pause();
    }

   } else if (focusChange == AudioManager.AUDIOFOCUS_GAIN) {
    if(mediaPlayer==null){
     initBeepSound();
    }else if(!mediaPlayer.isPlaying()){

     mediaPlayer.start();

    }
    // Resume playback
   } else if (focusChange == AudioManager.AUDIOFOCUS_LOSS) {
    if(mediaPlayer.isPlaying()){

     mediaPlayer.stop();
    }
    am.abandonAudioFocus(afChangeListener);
    // Stop playback
   }else if(focusChange==AudioManager.AUDIOFOCUS_REQUEST_GRANTED){
    if (mediaPlayer.isPlaying()) {
     mediaPlayer.stop();
    }

   }else if(focusChange==AudioManager.AUDIOFOCUS_REQUEST_FAILED){
    if(mediaPlayer.isPlaying()){
     mediaPlayer.stop();
    }

   }
  }
};
3.就是在我们播放音乐的时候为AudioManager添加获取焦点的监听

int result = am.requestAudioFocus(afChangeListener,
    // Use the music stream.
      AudioManager.STREAM_MUSIC, // Request permanent focus.
      AudioManager.AUDIOFOCUS_GAIN);
    if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
     mediaPlayer.start();
     // Start playback. // 开始播放音乐文件
    }

4.在我们不用的时候将焦点释放掉一般我们是在ondestroy()方法中释放

@Override
protected void onStop() {
  // TODO Auto-generated method stub
  super.onStop();
  am.abandonAudioFocus(afChangeListener);

}

下面介绍一下AudioManager的几个常量

AUDIOFOCUS_REQUEST_GRANTED 永久获取媒体焦点（播放音乐）

AUDIOFOCUS_GAIN_TRANSIENT 暂时获取焦点适用于短暂的音频

AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK Duck我们应用跟其他应用共用焦点我们播放的时候其他音频会降低音量

下面奉上代码

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 package com.example.mediatest;  
   
 import java.io.IOException;  
   
 import android.app.Activity;  
 import android.content.BroadcastReceiver;  
 import android.content.ComponentName;  
 import android.content.Context;  
 import android.content.Intent;  
 import android.content.res.AssetFileDescriptor;  
 import android.media.AudioManager;  
 import android.media.AudioManager.OnAudioFocusChangeListener;  
 import android.media.MediaPlayer;  
 import android.media.MediaPlayer.OnCompletionListener;  
 import android.os.Bundle;  
 import android.view.KeyEvent;  
 import android.view.Menu;  
 import android.view.View;  
 import android.view.View.OnClickListener;  
 import android.widget.Button;  
 import android.widget.Toast;  
   
 public class MainActivity extends Activity {  
   
     private Button play;  
     private Button stop;  
     private AudioManager am;  
     @Override  
     protected void onCreate(Bundle savedInstanceState) {  
         super.onCreate(savedInstanceState);  
         setContentView(R.layout.activity_main);  
         play = (Button) findViewById(R.id.button1);  
         stop = (Button) findViewById(R.id.button2);  
         am = (AudioManager) getSystemService(Context.AUDIO_SERVICE);  
         initBeepSound();  
         mode = am.getMode();  
         if (mode == AudioManager.MODE_NORMAL) {  
             Toast.makeText(this, "MODE_NORMAL", Toast.LENGTH_LONG).show();  
         } else if (mode == AudioManager.MODE_IN_CALL) {  
             Toast.makeText(this, "MODE_IN_CALL", Toast.LENGTH_LONG).show();  
   
         } else if (mode == AudioManager.MODE_RINGTONE) {  
             Toast.makeText(this, "MODE_RINGTONE", Toast.LENGTH_LONG).show();  
   
         }  
         remoteControlReceiver = new ComponentName(" com.example.mediatest",  
                 " com.example.mediatest.RemoteControlReceiver");  
         play.setOnClickListener(new OnClickListener() {  
   
             @Override  
             public void onClick(View v) {  
                 if (mediaPlayer != null) {  
                     mediaPlayer.start();  
   
                 } else {  
                     initBeepSound();  
                     mediaPlayer.start();  
                 }  
                 // Request audio focus for playback  
                 int result = am.requestAudioFocus(afChangeListener,  
                 // Use the music stream.  
                         AudioManager.STREAM_MUSIC, // Request permanent focus.  
                         AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK);  
                 if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {  
                     mediaPlayer.start();  
                     // Start playback. // 开始播放音乐文件  
                 }  
             }  
   
         });  
         stop.setOnClickListener(new OnClickListener() {  
   
             @Override  
             public void onClick(View v) {  
                 if (mediaPlayer != null && mediaPlayer.isPlaying()) {  
                     mediaPlayer.stop();  
                     mediaPlayer.release();  
                     mediaPlayer = null;  
                 }  
                 am.abandonAudioFocus(afChangeListener);  
             }  
         });  
     }  
   
     OnAudioFocusChangeListener afChangeListener = new OnAudioFocusChangeListener() {  
         public void onAudioFocusChange(int focusChange) {  
             if (focusChange == AudioManager.AUDIOFOCUS_LOSS_TRANSIENT) {  
                 if (mediaPlayer.isPlaying()) {  
                     mediaPlayer.pause();  
                 }  
   
             } else if (focusChange == AudioManager.AUDIOFOCUS_GAIN) {  
                 if (mediaPlayer == null) {  
                     initBeepSound();  
                 } else if (!mediaPlayer.isPlaying()) {  
   
                     mediaPlayer.start();  
   
                 }  
                 // Resume playback  
             } else if (focusChange == AudioManager.AUDIOFOCUS_LOSS) {  
                 if (mediaPlayer.isPlaying()) {  
   
                     mediaPlayer.stop();  
                 }  
                 am.abandonAudioFocus(afChangeListener);  
                 // Stop playback  
             } else if (focusChange == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {  
                 if (mediaPlayer.isPlaying()) {  
                     mediaPlayer.stop();  
                 }  
   
             } else if (focusChange == AudioManager.AUDIOFOCUS_REQUEST_FAILED) {  
                 if (mediaPlayer.isPlaying()) {  
                     mediaPlayer.stop();  
                 }  
   
             }  
         }  
     };  
     /** 
      * When the beep has finished playing, rewind to queue up another one. 
      */  
     private final OnCompletionListener beepListener = new OnCompletionListener() {  
         public void onCompletion(MediaPlayer mediaPlayer) {  
             mediaPlayer.seekTo(0);  
         }  
     };  
     private MediaPlayer mediaPlayer;  
     private ComponentName remoteControlReceiver;  
     private int mode;  
   
     private void initBeepSound() {  
         if (mediaPlayer == null) {  
             // The volume on STREAM_SYSTEM is not adjustable, and users found it  
             // too loud,  
             // so we now play on the music stream.  
             setVolumeControlStream(AudioManager.STREAM_MUSIC);  
             mediaPlayer = new MediaPlayer();  
             mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);  
             mediaPlayer.setOnCompletionListener(beepListener);  
   
             AssetFileDescriptor file = getResources().openRawResourceFd(  
                     R.raw.demo);  
             try {  
                 mediaPlayer.setDataSource(file.getFileDescriptor(),  
                         file.getStartOffset(), file.getLength());  
                 file.close();  
                 mediaPlayer.prepare();  
             } catch (IOException e) {  
                 mediaPlayer = null;  
             }  
         }  
     }  
   
     @Override  
     protected void onStop() {  
         // TODO Auto-generated method stub  
         super.onStop();  
         am.abandonAudioFocus(afChangeListener);  
   
     }  
   
     @Override  
     public boolean onCreateOptionsMenu(Menu menu) {  
         // Inflate the menu; this adds items to the action bar if it is present.  
         getMenuInflater().inflate(R.menu.main, menu);  
         return true;  
     }  
   
 }  