在播放声音之前，后退按钮不起作用

Question

我正在开发类似MP3的应用程序。我现在面临的问题是，在播放声音之前，后退按钮无效。如果我没有播放任何声音，它说，“不幸的是，MP3停止了”帮助我。

（抱歉英语不好）

这是我的代码

@Override
public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.headerfooter);

    ScrollView scrollable_contents = (ScrollView) findViewById(R.id.scrollablecontents);
    getLayoutInflater().inflate(R.layout.filxml, scrollable_contents);

    btnReturn1 = (Button)findViewById(R.id.back);
    btnReturn1.setOnClickListener(new OnClickListener()
    {
        public void onClick(View v) 
        {
            finish();
        }
    });

    title = (TextView)findViewById(R.id.title);
    title.setText("Surah Al FIL (105)");
    play = (Button)findViewById(R.id.play);
    stop = (Button)findViewById(R.id.stop);  
    pause = (Button)findViewById(R.id.pause);
    play1=(ImageButton)findViewById(R.id.fil1);
    play2=(ImageButton)findViewById(R.id.fil2);
    play3=(ImageButton)findViewById(R.id.fil3);
    play4=(ImageButton)findViewById(R.id.fil4);
    play5=(ImageButton)findViewById(R.id.fil5);


    play.setOnClickListener(new OnClickListener()
    {   
        @Override
        public void onClick(View v)
        {
            play_all();

        }
    });

    stop.setOnClickListener(new OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            stopall();

        }
    });
    pause.setOnClickListener(new OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            pause();

        }
    });

    play1.setOnClickListener(new OnClickListener()
    {
         @Override
        public void onClick(View v)
         {

            go();
         }


    });
    play2.setOnClickListener(new OnClickListener()
    {
         @Override
        public void onClick(View v)
         {

            go1();
         }


    });
    play3.setOnClickListener(new OnClickListener()
    {
         @Override
        public void onClick(View v)
         {

            go2();
         }


    });
    play4.setOnClickListener(new OnClickListener()
    {
         @Override
        public void onClick(View v)
         {

            go3();
         }


    });
    play5.setOnClickListener(new OnClickListener()
    {
         @Override
        public void onClick(View v)
         {

            go4();
         }


    });
}

public void play_all()
{
    stopPlaying();
    if(mp != null && mp.isPlaying())
    {
        mp.stop();
        mp.release();
        mp = null;

    }
        mp = MediaPlayer.create(this,R.raw.fil_full);
        mp.setLooping(true);
        mp.start();
}
public void stopall()
{
    if(mp.isPlaying())
        mp.stop();

}
public void pause()
{
    if(mp.isPlaying())
        mp.pause();
    else
        mp.reset();
}

public void go() 
{
    stopPlaying();
    if(mp != null && mp.isPlaying())
    {
        mp.stop();
        mp.release();
        mp = null;
    }
        mp = MediaPlayer.create(this,R.raw.fil1);
        mp.setLooping(true);
        mp.start();
}
public void go1() 
{
    if(mp != null && mp.isPlaying())
    {
        mp.stop();
        mp.release();
        mp = null;
    }
        mp = MediaPlayer.create(this,R.raw.fil2);
        mp.start();
}
public void go2() 
{
    if(mp != null && mp.isPlaying())
    {
        mp.stop();
        mp.release();
        mp = null;
    }
        mp = MediaPlayer.create(this,R.raw.fil3);
        mp.start();
}
public void go3() 
{if(mp != null && mp.isPlaying())
    {
        mp.stop();
        mp.release();
        mp = null;
    }
        mp = MediaPlayer.create(this,R.raw.fil4);
        mp.start();
}
public void go4() 
{
    if(mp != null && mp.isPlaying())
    {
        mp.stop();
        mp.release();
        mp = null;
    }
        mp = MediaPlayer.create(this,R.raw.fil5);
        mp.start();
}

//@Override
protected void onPause() {
    // TODO Auto-generated method stub
    super.onPause();
    mp.stop();
}
@Override
protected void onDestroy() {
    // TODO Auto-generated method stub
    super.onDestroy();
    mp.stop();
}

private void stopPlaying() 
{
    if (mp != null) {
        mp.stop();
        mp.release();
        mp = null;
   }
}

}