AudioManager 播放声音

可以以左声道或者右声道来播放音频文件：
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.media.MediaPlayer;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.media.AudioFormat;

public class LRChannel extends Activity {
    private Button lButton;
    private Button rButton;
    private TextView myTextView;
    private MediaPlayer mMediaPlayer01 = null;
    private AudioTrack aAudioTrack01 = null;
    private String strFilePath = "/sdcard/test.mp3";
    private float midVol = 0;
    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        lButton = (Button) findViewById(R.id.ButtonL);
        rButton = (Button) findViewById(R.id.ButtonR);
        myTextView = (TextView) findViewById(R.id.myTextView);
        
        // left button response
        lButton.setOnClickListener(new Button.OnClickListener()
        {
          @Override
          public void onClick(View arg0)
          {
            // if ( checkSDCard() )
            // {
                // playVideo(strFilePath);
                playSound(strFilePath, 0);
            // }
          }
        });
        
        // right button response
        rButton.setOnClickListener(new Button.OnClickListener()
        {
          @Override
          public void onClick(View arg0)
          {
              playSound(strFilePath, 1);
          }
        });
    }
    
    private void playVideo(String strPath)
    {
        mMediaPlayer01 = new MediaPlayer();
        mMediaPlayer01.setAudioStreamType(AudioManager.STREAM_MUSIC);
        
        try
        { 
            mMediaPlayer01.setDataSource(strPath); 
        }
        catch (Exception e)
        { 
            // TODO Auto-generated catch block
            myTextView.setText("setDataSource Exceeption:" + e.toString());
            e.printStackTrace();
        }
        
        try
        { 
            mMediaPlayer01.prepare();
        }
        catch (Exception e)
        { 
            // TODO Auto-generated catch block
            myTextView.setText("prepare Exceeption:"+e.toString());
            e.printStackTrace();
        }
        
        mMediaPlayer01.start();
        myTextView.setText("Playing");
        
        mMediaPlayer01.setOnCompletionListener(new MediaPlayer.OnCompletionListener()
        {
            public void onCompletion(MediaPlayer arg0)
            {
                // TODO Auto-generated method stub
                myTextView.setText("Playing stop!");
            }
        });
    }
    
    // iChannel = 0 means left channel test, iChannel = 1 means right channel test.
    private void playSound(String strPath, int iChannel)
    {
      // If now is playing...
      if ( aAudioTrack01 != null )
      {
          aAudioTrack01.release();
          aAudioTrack01 = null;
      }
      // Get the AudioTrack minimum buffer size
      int iMinBufSize = AudioTrack.getMinBufferSize(44100, 
                          AudioFormat.CHANNEL_CONFIGURATION_STEREO, 
                          AudioFormat.ENCODING_PCM_16BIT);
      if ( iMinBufSize == AudioTrack.ERROR_BAD_VALUE || iMinBufSize == AudioTrack.ERROR )
      {
          return;
      }
      // Constructor a AudioTrack object
      try
      {
          aAudioTrack01 = new AudioTrack(AudioManager.STREAM_MUSIC, 44100, 
                    AudioFormat.CHANNEL_CONFIGURATION_STEREO, 
                    AudioFormat.ENCODING_PCM_16BIT, 
                    iMinBufSize, 
                    AudioTrack.MODE_STREAM);
      }
      catch (IllegalArgumentException iae)
      {
          myTextView.setText("new AudioTrack Exceeption:" + iae.toString());
          iae.printStackTrace();
      }
      // Write data to buffer
      byte data[] = new byte[iMinBufSize];
      aAudioTrack01.write(data, 0, data.length);
      aAudioTrack01.write(data, 0, data.length);
      float lValue = 0;
      float rValue = 0;
       
      if ( iChannel == 0 )
      {
          lValue = 1.0f;
          rValue = 0.0f;
      }
      else if ( iChannel == 1 )
      {
          lValue = 0.0f;
          rValue = 1.0f;
      }
      
      aAudioTrack01.play();
      if ( aAudioTrack01.setStereoVolume(lValue, rValue) == AudioTrack.SUCCESS )
      {
          myTextView.setText("setStereoVolume successfully!");
      }
      aAudioTrack01.stop();
      if ( aAudioTrack01.setStereoVolume(midVol, midVol) == AudioTrack.SUCCESS )
      {
          myTextView.setText("Restore setStereoVolume successfully!");
      }
      aAudioTrack01.release();
      aAudioTrack01 = null;
    }
    
    private boolean checkSDCard()
    {
      if ( android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED) )
      {
          return true;
      }
      else
      {
          return false;
      }
    }
    
    @Override
    protected void onDestroy() {
        super.onDestroy();
        // TODO Auto-generated method stub
        if ( aAudioTrack01 != null ) {
            aAudioTrack01.setStereoVolume(midVol, midVol);
            aAudioTrack01.release();
            aAudioTrack01 = null;
        }
    }
    
}