MP3歌曲无法在媒体播放器中播放

我在这里尝试下面的代码是MainActivity.java

import java.io.File;
import java.util.ArrayList;

import javax.crypto.spec.PSource;

import android.R.string;
import android.support.v7.app.ActionBarActivity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.os.Environment;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterViewFlipper;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {

    ListView lv;
    String[] items;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv =  (ListView) findViewById(R.id.lvPlaylist);
        final ArrayList<File> mySongs = findSongs(Environment.getExternalStorageDirectory());
        items =  new String[mySongs.size () ];
        for (int i = 0; i < mySongs.size(); i++) {
            //toast(mySongs.get(i).getName().toString());
            items[i] = mySongs.get(i).getName().toString();
        }

        ArrayAdapter<String> adp = new ArrayAdapter<String>(getApplicationContext(),R.layout.list_item,R.id.textView1,items);
        lv.setAdapter(adp);
        lv.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {
                // TODO Auto-generated method stub
                startActivity(new Intent(getApplicationContext(), player.class).putExtra("pos", position).putExtra("songlist",mySongs));
            }
        });
    }

    public ArrayList<File> findSongs(File root){
        ArrayList al = new ArrayList<File>();
        File[] files = root.listFiles();
        for(File singleFile : files){
            if (singleFile.isDirectory()&& !singleFile.isHidden()) {
                al.addAll(findSongs(singleFile));

            }
            else {
                if (singleFile.getName().endsWith(".mp3") || singleFile.getName().endsWith(".wav")) {
                    al.add(singleFile);
                }
            }
        }
        return al;
    }

    public void toast(String text) {
        Toast.makeText(getApplicationContext(), text, Toast.LENGTH_SHORT).show();

    }

    @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);
    }
}

上面的代码给我一个mp3文件列表，当我们点击播放器播放歌曲时播放的歌曲之一

和player.java

import java.io.File;
import java.util.ArrayList;
import android.content.Intent;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.widget.SimpleCursorAdapter.ViewBinder;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Button;
import android.widget.SeekBar;

public class player extends ActionBarActivity implements View.OnClickListener{
    static MediaPlayer mp;
    ArrayList<File> mySongs;
    int position;
    Uri u;

    SeekBar sb;
    Button btPv, btFB,btplay,btFF, btNxt;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_player);
        btFB = (Button) findViewById(R.id.btFB);
        btPv = (Button) findViewById(R.id.btPv);
        btplay = (Button) findViewById(R.id.btplay);
        btFF = (Button) findViewById(R.id.btFF);
        btNxt = (Button) findViewById(R.id.btNxt);

        btFB.setOnClickListener(this) ;
        btPv.setOnClickListener(this);
        btplay.setOnClickListener(this);
        btFF.setOnClickListener(this);
        btNxt.setOnClickListener(this);
//      
        if(mp != null)
        {
            mp.stop();
            mp.release();

        }


        Intent i = getIntent();
        Bundle  b = i.getExtras();
        mySongs = (ArrayList) b.getParcelableArrayList("songlist");
        position = b.getInt("pos", 0);
        u = Uri.parse(mySongs.get(position).toString());
        mp = MediaPlayer.create(getApplicationContext(), u).start();
        mp.start();
    }

    @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);
    }
    @Override
    public void onClick(View v)
    {
        int id = v.getId();
        switch (id) {
        case R.id.btplay:
            if(mp.isPlaying())
            {btplay.setText("play"); 
                mp.pause(); 
            }
            else
            {   btplay.setText("play"); 
                mp.start();
            }
            break;
        case R.id.btFF:
            mp.seekTo(mp.getCurrentPosition()+ 5000);
            break;
        case R.id.btFB:
            mp.seekTo(mp.getCurrentPosition()- 5000);
            break;
        case R.id.btNxt:
            mp.stop();
            mp.release();
            position = (position+1)%mySongs.size();
            u = Uri.parse(mySongs.get(position).toString());
            mp = MediaPlayer.create(getApplicationContext(), u);
            mp.start();
            break;
        case R.id.btPv :
            mp.stop();
            mp.release();
            // Important
            position =  (position-1<0) ?  mySongs.size()-1: position-1;
            /*if(position-1 < 0)

            {
                position = mySongs.size()-1;

            }
            else
            {
                position= position-1;
            }*/
            u = Uri.parse(mySongs.get(position).toString());
            mp = MediaPlayer.create(getApplicationContext(), u);
            mp.start();
        default:
            break;
        }
    }

}

虽然上面的代码适用于少数几首mp3的歌曲，但它不适用于其他也是mp3的歌曲 . 我已经在实际设备上试过这个应用程序只会崩溃如果这首歌有问题的mp3文件让我的问题在其他媒体播放器甚至默认的Android媒体播放器上完美运行

究竟是什么问题？