如何停止已经播放的声音并立即开始播放

Question

当播放用户先前选择的声音时，如何停止播放该声音并立即播放新选择的声音？ 到目前为止，我拥有的代码只能停止新声音，但是用户必须再次选择声音才能播放。

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;
                }
            }
        }
        );

我正在制作具有30多种声音的音板，如果有帮助的话。 我需要对代码进行哪些更改（我认为是轻微的）？ 任何帮助将不胜感激！

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;
            }
        });
    }
}