求教 MediaPlayer 音乐播放器 歌曲循环播放

package com.rj1b.medieplayerdemo;

import java.io.File;
import java.io.IOException;




import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.SeekBar;
import android.widget.TextView;
import android.os.Build;

public class MainActivity extends Activity implements
	SeekBar.OnSeekBarChangeListener, View.OnClickListener {
	SeekBar skb;
	TextView totaltv, playtv;
	Button play, pause, stop;
	List pathlist;
	int corrent=0;
	public static void aa(){
		
	}
	
	//创建媒体播放对象
	MediaPlayer mplayer;
	Handler handler=new Handler();
	boolean hadDestroy=false;
	
	Runnable runs=new Runnable(){

		@Override
		public void run() {
			// TODO Auto-generated method stub
			if(!hadDestroy){
			handler.postDelayed(this, 500);
			int currentTime =Math.round(mplayer.getCurrentPosition()/1000);
			String playTime=String.format("%02d:%02d",currentTime/60,currentTime%60);
			playtv.setText(playTime);
			
			skb.setProgress(mplayer.getCurrentPosition());
			
			
		}
		}
		
	};
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		skb = (SeekBar) this.findViewById(R.id.seekBar1);
		
		
		totaltv = (TextView) this.findViewById(R.id.totaltv);
		playtv = (TextView) this.findViewById(R.id.playtv);
		
		
		play = (Button) this.findViewById(R.id.play);
		pause = (Button) this.findViewById(R.id.pause);
		stop = (Button) this.findViewById(R.id.stop);
		
		
		play.setOnClickListener(this);
		pause.setOnClickListener(this);
		stop.setOnClickListener(this);

		skb.setOnSeekBarChangeListener(this);
	
			
		 mplayer =new MediaPlayer();
		 
		 
		 mplayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
				
				@Override
				public void onCompletion(MediaPlayer mp) {
					// TODO Auto-generated method stub
					if(corrent==pathlist.size()-1){
						//mplayer.isPlaying();
						corrent=0;
						//System.out.println(pathlist.size());
					}else{
					corrent++;
					}
					/*for(int corrent=0;corrent==pathlist.size()-1;corrent++){
						System.out.print("下一首");
						
					}*/
					 initMediaPler();
					 mplayer.start();
					 
				}
			});
		 
		 
		 initMediaPler();


		/*
		 * if (savedInstanceState == null) {
		 * getFragmentManager().beginTransaction() .add(R.id.container, new
		 * PlaceholderFragment()).commit(); }
		 */
	}

		
		private void initMediaPler() {
		// TODO Auto-generated method stub
			pathlist=new ArrayList();
			
			File file1=new File(Environment.getExternalStorageDirectory()+"/music/"
			+"englishworld-Happy Birthday.mp3");
	File file2=new File(Environment.getExternalStorageDirectory()+"/music/"
		+"englishsong-renguiqingweiliao.mp3");
		pathlist.add(file1.getPath());
		pathlist.add(file2.getPath());
		
		
	
		try {
			mplayer.setDataSource(pathlist.get(corrent));
			//Log.d("path", file.getPath());
			mplayer.prepare();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} 
	}


		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			switch(v.getId()){
			case R.id.play:
				if(!mplayer.isPlaying()){
					mplayer.start();
					int totalTime=Math.round(mplayer.getDuration()/1000);
					String totalstr=String.format("%02d:%02d", totalTime/60,totalTime%60);
							totaltv.setText(totalstr);
							skb.setMax(mplayer.getDuration());
							handler.postDelayed(runs, 500);
							}
				break;
			case R.id.pause:
				if(mplayer.isPlaying()){
					mplayer.pause();
				}
				break;
			case R.id.stop:
				if(mplayer.isPlaying()){
					mplayer.reset();
					initMediaPler();
				}
				break;
				
			}
		}

		@Override
		public void onProgressChanged(SeekBar seekBar, int progress,
				boolean fromUser) {
			// TODO Auto-generated method stub
			if(mplayer!=null){
				
			if(fromUser){
				//skb.setProgress(progress);
				
				mplayer.seekTo(progress);
			}
			}
			
		}

		@Override
		public void onStartTrackingTouch(SeekBar seekBar) {
			// TODO Auto-generated method stub
			
		}

		@Override
		public void onStopTrackingTouch(SeekBar seekBar) {
			// TODO Auto-generated method stub
			
		}
	@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;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		// Handle action bar item clicks here. The action bar will
		// automatically handle clicks on the Home/Up button, so long
		// as you specify a parent activity in AndroidManifest.xml.
		int id = item.getItemId();
		if (id == R.id.action_settings) {
			return true;
		}
		return super.onOptionsItemSelected(item);
	}

	/**
	 * A placeholder fragment containing a simple view.
	 */
	public static class PlaceholderFragment extends Fragment {

		public PlaceholderFragment() {
		}

		@Override
		public View onCreateView(LayoutInflater inflater, ViewGroup container,
				Bundle savedInstanceState) {
			View rootView = inflater.inflate(R.layout.fragment_main, container,
					false);
			return rootView;
		}
	}

	/* (non-Javadoc)
	 * @see android.app.Activity#onDestroy()
	 */
	@Override
	protected void onDestroy() {
		// TODO Auto-generated method stub
		super.onDestroy();
		if(mplayer!=null){
			mplayer.stop();
			hadDestroy=true;
			mplayer.release();
		}
		
	}
	

}

有问题 但是不会用Debug调试 求大神帮忙调试

下面是布局代码

权限加载为： android.permission.READ_EXTERNAL_STORAGE