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();
}
}