Question

我想在运行时创建一个按钮。按下该按钮应该在按下时开始播放声音，并在用户停止按下按钮时停止播放。

浏览网页和Stack Overflow我想出了这段代码：

    // Create a new button and place it into a table row
    LinearLayout lnr = (LinearLayout) findViewById(R.id.tableRow3);
    Button b1 = new Button(this);
    lnr.addView(b1);

    // Associate the event
    b1.setOnTouchListener(new OnTouchListener() {
        MediaPlayer mp = new MediaPlayer();
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            switch(event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                // Finger started pressing --> play sound in loop mode
                try {
                    FileInputStream fileInputStream = new FileInputStream( PATH );
                    mp.setDataSource(fileInputStream.getFD());
                    mp.prepare();
                    mp.setLooping(true);
                    mp.start();
                } catch (Exception e) {}
            case MotionEvent.ACTION_UP:
                // Finger released --> stop playback
                try {
                    mp.stop();
                } catch (Exception e) {} 
          }
          return true;
        }
      });

问题在于我根本听不到声音。在我看来，case MotionEvent.ACTION_UP:是直接触发的。因此，播放将直接停止。

为了测试这个假设，我删除了mp.stop();并听到了无限循环的声音。很明显，它必须是ACTION_UP事件，搞砸了一切。但是，如果我不释放手指/鼠标，怎么能触发ACTION_UP事件？

Answer 1

您应该插入＆＃39; 中断＆＃39;位于＆＃39;案例底部的MotionEvent.ACTION_DOWN＆＃39;。

Answer 2

正确的代码是：

    // Create a new button and place it into a table row
    LinearLayout lnr = (LinearLayout) findViewById(R.id.tableRow3);
    Button b1 = new Button(this);
    lnr.addView(b1);

    // Associate the event
    b1.setOnTouchListener(new OnTouchListener() {
        MediaPlayer mp = new MediaPlayer();
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            switch(event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                // Finger started pressing --> play sound in loop mode
                try {
                    FileInputStream fileInputStream = new FileInputStream( PATH );
                    mp.setDataSource(fileInputStream.getFD());
                    mp.prepare();
                    mp.setLooping(true);
                    mp.start();
                } catch (Exception e) {}
            break;
            case MotionEvent.ACTION_UP:
                // Finger released --> stop playback
                try {
                    mp.stop();
                    mp.reset();
                } catch (Exception e) {}
            break;
          }
          return true;
        }
      });

在运行期间为Action_Down和_up添加一个onTouch事件，以便在按下按钮时播放声音

2 个答案: