Android播播放完SD卡指定文件夹音乐之后，自动播放下一首

package com.example.asyncplayer_ex;

import java.io.IOException;
import java.util.ArrayList;

import javax.security.auth.PrivateCredentialPermission;

import android.app.Activity;
import android.drm.DrmStore.Playback;
import android.media.AsyncPlayer;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends Activity {
    private static final String TAG = "MP3";
    private AsyncPlayer asyncPlayer = new AsyncPlayer(null); 
    private String path;
    private MediaPlayer mediaPlayer;
    private int songIndex = 0;
    private ArrayList<String> songArrayList; //播放声音列表
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        mediaPlayer = new MediaPlayer();
        mediaPlayer.setOnCompletionListener(new CompletionListener());
        path = Environment.getExternalStorageDirectory().toString() + "/mp3/Voice/";
        songArrayList = new ArrayList<String>();
        songArrayList.add(path + "1.MP3");
        songArrayList.add(path + "2.MP3");
        songArrayList.add(path + "3.MP3");
        songArrayList.add(path + "4.MP3");
        songArrayList.add(path + "5.MP3");
        songArrayList.add(path + "6.MP3");
        songplay();        
    }
    
    private final class CompletionListener implements OnCompletionListener{

        @Override
        public void onCompletion(MediaPlayer mp) {
            nextsong();            
        }        
        
    }
    private void nextsong() {
        
        if (songIndex < songArrayList.size() - 1) {    
            songIndex = songIndex + 1;
            songplay();            
        }
        else {
            songArrayList.clear();
            songIndex = 0;

        }
        
        
    }
    private void songplay() {
        try {
            mediaPlayer.reset();
            mediaPlayer.setDataSource(songArrayList.get(songIndex));
            mediaPlayer.prepare();
            mediaPlayer.start();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SecurityException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalStateException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }

    @Override
    protected void onDestroy() {
        mediaPlayer.release();
        mediaPlayer = null;
        super.onDestroy();
    }
}