通过实例验证播放本地音乐MediaPlayer的reset函数并不会阻塞主线程

如题，通过下面的一个例子，频繁点击播放下一首歌，验证MediaPlayer的reset函数是否会发生阻塞。

验证数据如下：在从20:26:04.673到20:26:36.168的32秒时间内，点击170次Next播放下一首歌曲，都成功，没有发生阻塞主线程导致ANR的问题。

由于本例播放的都是本地歌曲 ，所以没有发生阻塞的情况。如果是播放在线歌曲，需要与网络交换，频繁执行播放动作，可能会发生ANR；播放网络歌曲需要使用异步的prepareAsync函数，而不能使用同步的prepare，以免发生阻塞。

（1）第一次播放的log如下：

06-24 20:26:04.673 26426 26426 D MainActivity: -------------------------------
06-24 20:26:04.678 26426 26426 D MainActivity: play next music
06-24 20:26:04.678 26426 26426 D MainActivity: before reset
06-24 20:26:04.683 26426 26426 D MainActivity: after reset
06-24 20:26:04.683 26426 26426 D MainActivity: before setDataSource:/mnt/sdcard/Music/白安/麦田捕手-白安.mp3
06-24 20:26:04.763 26426 26426 D MainActivity: after setDataSource to prepare
06-24 20:26:04.768 26426 26426 D MainActivity: onPrepared
06-24 20:26:04.898 26426 26426 D MainActivity: -------------------------------

（2）最后6次播放的log如下：

06-24 20:26:35.013 26426 26426 D MainActivity: -------------------------------
06-24 20:26:35.013 26426 26426 D MainActivity: play next music
06-24 20:26:35.013 26426 26426 D MainActivity: before reset
06-24 20:26:35.018 26426 26426 D MainActivity: after reset
06-24 20:26:35.018 26426 26426 D MainActivity: before setDataSource:/mnt/sdcard/Music/Download/余生一起过-刘德华.aac
06-24 20:26:35.068 26426 26426 D MainActivity: after setDataSource to prepare
06-24 20:26:35.073 26426 26426 D MainActivity: onPrepared
06-24 20:26:35.213 26426 26426 D MainActivity: -------------------------------
06-24 20:26:35.213 26426 26426 D MainActivity: play next music
06-24 20:26:35.213 26426 26426 D MainActivity: before reset
06-24 20:26:35.218 26426 26426 D MainActivity: after reset
06-24 20:26:35.218 26426 26426 D MainActivity: before setDataSource:/mnt/sdcard/Music/白安/麦田捕手-白安.mp3
06-24 20:26:35.298 26426 26426 D MainActivity: after setDataSource to prepare
06-24 20:26:35.308 26426 26426 D MainActivity: onPrepared
06-24 20:26:35.403 26426 26426 D MainActivity: -------------------------------
06-24 20:26:35.403 26426 26426 D MainActivity: play next music
06-24 20:26:35.403 26426 26426 D MainActivity: before reset
06-24 20:26:35.403 26426 26426 D MainActivity: after reset
06-24 20:26:35.403 26426 26426 D MainActivity: before setDataSource:/mnt/sdcard/Music/Download/幸福就是-刘若英.mp3
06-24 20:26:35.463 26426 26426 D MainActivity: after setDataSource to prepare
06-24 20:26:35.463 26426 26426 D MainActivity: onPrepared
06-24 20:26:35.593 26426 26426 D MainActivity: -------------------------------
06-24 20:26:35.593 26426 26426 D MainActivity: play next music
06-24 20:26:35.593 26426 26426 D MainActivity: before reset
06-24 20:26:35.598 26426 26426 D MainActivity: after reset
06-24 20:26:35.598 26426 26426 D MainActivity: before setDataSource:/mnt/sdcard/Music/Download/余生一起过-刘德华.aac
06-24 20:26:35.678 26426 26426 D MainActivity: after setDataSource to prepare
06-24 20:26:35.683 26426 26426 D MainActivity: onPrepared
06-24 20:26:35.983 26426 26426 D MainActivity: -------------------------------
06-24 20:26:35.983 26426 26426 D MainActivity: play next music
06-24 20:26:35.983 26426 26426 D MainActivity: before reset
06-24 20:26:35.983 26426 26426 D MainActivity: after reset
06-24 20:26:35.983 26426 26426 D MainActivity: before setDataSource:/mnt/sdcard/Music/白安/麦田捕手-白安.mp3
06-24 20:26:36.068 26426 26426 D MainActivity: after setDataSource to prepare
06-24 20:26:36.073 26426 26426 D MainActivity: onPrepared
06-24 20:26:36.168 26426 26426 D MainActivity: -------------------------------
06-24 20:26:36.168 26426 26426 D MainActivity: play next music
06-24 20:26:36.168 26426 26426 D MainActivity: before reset
06-24 20:26:36.173 26426 26426 D MainActivity: after reset
06-24 20:26:36.173 26426 26426 D MainActivity: before setDataSource:/mnt/sdcard/Music/Download/幸福就是-刘若英.mp3
06-24 20:26:36.238 26426 26426 D MainActivity: after setDataSource to prepare
06-24 20:26:36.243 26426 26426 D MainActivity: onPrepared

（3）执行reset前后的log如下，reset在极短的时间内就会执行完毕，一般在10毫秒以内。

3:06-24 20:26:04.678 26426 26426 D MainActivity: before reset
4:06-24 20:26:04.683 26426 26426 D MainActivity: after reset
10:06-24 20:26:04.898 26426 26426 D MainActivity: before reset
11:06-24 20:26:04.898 26426 26426 D MainActivity: after reset
17:06-24 20:26:05.063 26426 26426 D MainActivity: before reset
18:06-24 20:26:05.068 26426 26426 D MainActivity: after reset
24:06-24 20:26:05.243 26426 26426 D MainActivity: before reset
25:06-24 20:26:05.243 26426 26426 D MainActivity: after reset
31:06-24 20:26:05.578 26426 26426 D MainActivity: before reset
32:06-24 20:26:05.583 26426 26426 D MainActivity: after reset
38:06-24 20:26:05.758 26426 26426 D MainActivity: before reset
39:06-24 20:26:05.763 26426 26426 D MainActivity: after reset
45:06-24 20:26:05.918 26426 26426 D MainActivity: before reset
46:06-24 20:26:05.918 26426 26426 D MainActivity: after reset
52:06-24 20:26:06.098 26426 26426 D MainActivity: before reset
53:06-24 20:26:06.098 26426 26426 D MainActivity: after reset
......

1144:06-24 20:26:34.838 26426 26426 D MainActivity: before reset
1145:06-24 20:26:34.838 26426 26426 D MainActivity: after reset
1151:06-24 20:26:35.013 26426 26426 D MainActivity: before reset
1152:06-24 20:26:35.018 26426 26426 D MainActivity: after reset
1158:06-24 20:26:35.213 26426 26426 D MainActivity: before reset
1159:06-24 20:26:35.218 26426 26426 D MainActivity: after reset
1165:06-24 20:26:35.403 26426 26426 D MainActivity: before reset
1166:06-24 20:26:35.403 26426 26426 D MainActivity: after reset
1172:06-24 20:26:35.593 26426 26426 D MainActivity: before reset
1173:06-24 20:26:35.598 26426 26426 D MainActivity: after reset
1179:06-24 20:26:35.983 26426 26426 D MainActivity: before reset
1180:06-24 20:26:35.983 26426 26426 D MainActivity: after reset
1186:06-24 20:26:36.168 26426 26426 D MainActivity: before reset
1187:06-24 20:26:36.173 26426 26426 D MainActivity: after reset

（4）验证代码如下：

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public class MainActivity extends Activity implements View.OnClickListener
{

    private static final String TAG = "MainActivity";

    private MediaPlayer mMediaPlayer = null;
    private Button mBtnPlayStop;
    private Button mBtnNext;
    
    private boolean mIsPlayFlag = false;
    
    private String mPathArray[] = new String[] {
      "/mnt/sdcard/Music/白安/麦田捕手-白安.mp3",
      "/mnt/sdcard/Music/Download/幸福就是-刘若英.mp3",
      "/mnt/sdcard/Music/Download/余生一起过-刘德华.aac"
    };
    private int mIndex = 0;

    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        mBtnPlayStop = (Button)findViewById(R.id.btnPlayStop);
        mBtnPlayStop.setOnClickListener(this);
        
        mBtnNext = (Button)findViewById(R.id.btnNext);
        mBtnNext.setOnClickListener(this);
        
        setVolumeControlStream(AudioManager.STREAM_MUSIC);

        mMediaPlayer = new MediaPlayer();
        mMediaPlayer.setOnPreparedListener(new OnPreparedListener() {

            @Override
            public void onPrepared(MediaPlayer arg0) {
                Log.d(TAG, "onPrepared");
                mMediaPlayer.start();
            }
            
        });
        mMediaPlayer.setOnCompletionListener(new OnCompletionListener()
        {

            @Override
            public void onCompletion(MediaPlayer mp)
            {
                Log.d(TAG, "onCompletion");
                next();
            }
        });
        mMediaPlayer.setOnErrorListener(new OnErrorListener() {

            @Override
            public boolean onError(MediaPlayer mp, int what, int extra) {
                Log.d(TAG, "onError what:" + what + ", extra:" + extra);
                
                return false;
            }
            
        });

    }

    @Override
    public void onClick(View v) {
        switch (v.getId())  
        {  
        case R.id.btnPlayStop:
            if (mIsPlayFlag) {
                try {
                    Log.d(TAG,"-------------------------------");
                    Log.d(TAG, "play:" + mPathArray[mIndex]);
                    Log.d(TAG, "before reset");
                    mMediaPlayer.reset();
                    Log.d(TAG, "after reset");
                    
                    Log.d(TAG, "before setDataSource");
                    mMediaPlayer.setDataSource(mPathArray[mIndex]);
                    Log.d(TAG, "after setDataSource to prepare");
                    mMediaPlayer.prepare();
                } catch (Exception e) {
                    e.printStackTrace();
                }
                mBtnPlayStop.setText("Stop");
            } else {
                Log.d(TAG,"-------------------------------");
                Log.d(TAG, "stop" + mPathArray[mIndex]);
                mMediaPlayer.stop();
                mBtnPlayStop.setText("Play");
            }
            
            mIsPlayFlag = !mIsPlayFlag;
            break;

        case R.id.btnNext:
            Log.d(TAG,"-------------------------------");
            Log.d(TAG, "play next music");
            next();
            break;
        }  
    }

 
    private void next() {
        try {
            Log.d(TAG, "before reset");
            mMediaPlayer.reset();
            Log.d(TAG, "after reset");
            
            if (mIndex < mPathArray.length - 1) {
                mIndex++;
            } else {
                mIndex = 0;
            }
            Log.d(TAG, "before setDataSource:" + mPathArray[mIndex]);
            mMediaPlayer.setDataSource(mPathArray[mIndex]);
            Log.d(TAG, "after setDataSource to prepare");
            mMediaPlayer.prepare();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

最后

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