Android ใช้ Mediaplayer แล้วพอกดปุ่ม Button ให้เล่นเสียง พอกดซ้อนกันแล้วเสียงมันซ้อน

import android.app.Activity;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;

/**
 * Created by Dell on 26/6/2556.
 */
public class gun_fire3 extends Activity implements View.OnClickListener {

    ImageView img,img2,img3,img4,img5,img6,img7,img8;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.four_activity);
        init();
        img.setOnClickListener(this);
        img2.setOnClickListener(this);
        img3.setOnClickListener(this);
        img4.setOnClickListener(this);
        img5.setOnClickListener(this);
        img6.setOnClickListener(this);
        img7.setOnClickListener(this);

    }

    private void init()
    {

        img  = (ImageView) findViewById(R.id.imageView);
        img2 = (ImageView) findViewById(R.id.imageView2);
        img3 = (ImageView) findViewById(R.id.imageView3);
        img4 = (ImageView) findViewById(R.id.imageView4);
        img5 = (ImageView) findViewById(R.id.imageView5);
        img6 = (ImageView) findViewById(R.id.imageView6);
        img7 = (ImageView) findViewById(R.id.imageView7);


    }

    @Override
    public void onClick(View view) {

       MediaPlayer media;
        if (view.getId()==R.id.imageView)
        {
            media = MediaPlayer.create(getBaseContext(),R.raw.sniper_b);
            media.start();
        }
        else if (view.getId()==R.id.imageView2)
        {
             media = MediaPlayer.create(getBaseContext(),R.raw.sniper_c);
            media.start();

        }

        else if (view.getId()==R.id.imageView3)
        {
            media = MediaPlayer.create(getBaseContext(),R.raw.bomb_a);
            media.start();
        }

        else if (view.getId()==R.id.imageView4)
        {
             media = MediaPlayer.create(getBaseContext(),R.raw.laser_a);

            media.start();

        }

        else if (view.getId()==R.id.imageView5)
        {
            media = MediaPlayer.create(getBaseContext(),R.raw.laser_b);
            media.start();
        }

        else if (view.getId()==R.id.imageView6)
        {
            media = MediaPlayer.create(getBaseContext(),R.raw.war_a);
            media.start();
        }

        else if (view.getId()==R.id.imageView7)
        {
            media = MediaPlayer.create(getBaseContext(),R.raw.war_b);
            media.start();

        }

    }

    public void onBackPressed() {
        Intent obj = new Intent(gun_fire3.this,gun_fire2.class);
        startActivity(obj);
    }
}