How to stop already playing sound and immediately start another

Question

When a sound that the user previously selected is playing, how can I stop that sound and immediately play the new selected sound? The code I have so far only stops the new sound, but the user has to select the sound again in order to play it.

public class MainActivity extends Activity {
    public MediaPlayer mediaPlayer = null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button a = (Button) findViewById(R.id.First);
        a.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mediaPlayer == null) {
                    mediaPlayer = MediaPlayer.create(MainActivity.this, R.raw.firstsound);
                    mediaPlayer.stop();
                }
                else {
                    mediaPlayer.start();
                    mediaPlayer = null;
                }
            }
        }
        );
        Button b = (Button) findViewById(R.id.Second);
        b.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mediaPlayer == null) {
                    mediaPlayer = MediaPlayer.create(MainActivity.this, R.raw.secondsound);
                    mediaPlayer.stop();
                }
                else {
                    mediaPlayer.start();
                    mediaPlayer = null;
                }
            }
        }
        );

I am making a soundboard with over 30 sounds, if that helps at all. What (slight I assume) changes would I need to make to my code? Any help would be greatly appreciated!

Answer 1

public class MainActivity extends Activity {

    public MediaPlayer mediaPlayer = null;
    public Boolean playing=false;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button a = (Button) findViewById(R.id.First);
        a.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                (playing)mediaPlayer.stop();
                mediaPlayer = MediaPlayer.create(MainActivity.this, R.raw.firstsound);
                mediaPlayer.start();
                            playing=true;
            }

        });

        Button b = (Button) findViewById(R.id.Second);
        b.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                (playing)mediaPlayer.stop();
                mediaPlayer = MediaPlayer.create(MainActivity.this, R.raw.firstsound);
                mediaPlayer.start();
                            playing=true;
            }
        });
    }
}