android – GestureDetector onScroll()问题(执行3次)

我有这段代码来使用GestureDetector检测滚动手势.它工作,除了它检测滚动活动3次而不是一次.

如何只检测一次？它记录了滚动活动(log.i行)3次,并播放声音(mp.start)3次而不是一次….也导致我的应用程序强行关闭.

  public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {

        //get x and Y co-ordinates and log it as info. 
        float x1 = e1.getX();
        float y1 = e1.getY();
        float x2 = e2.getX();
        float y2 = e2.getY();       
        Log.i("Scroll_Gesture", "Scrolled from: (" + x1 + "," + y1 + " to " + x2 +"," + y2 + ")");

        mp = MediaPlayer.create(this, R.raw.scroll_success);        
        mp.start();

       //start success page
        Intent intent = new Intent(this, ScrollSuccess.class);
        startActivity(intent); 
        return false;
    }

解决方法:

“onScroll()”将被多次调用.
它被调用的次数取决于用户完成的滚动操作.

如果您希望代码块在每个滚动操作的开头只运行一次,那么您必须添加一个条件,如下所示：

   float scrollstartX1, scrollStartY1;

   public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
           float distanceY) {
    // get x and Y co-ordinates and log it as info.
       if (scrollstartX1 != e1.getX() || scrollStartY1 != e1.getY()) {
           scrollstartX1 = e1.getX();
           scrollStartY1 = e1.getY();
               //***************************************
           //code run only once for a scroll action...
               //****************************************
       }
           float x2 = e2.getX();
           float y2 = e2.getY();
           Log.i("Scroll_Gesture", "Scrolled from: (" + scrollstartX1 + "," + scrollStartY1 + " to "
                   + x2 + "," + y2 + ")");

           mp = MediaPlayer.create(this, R.raw.scroll_success);
           mp.start();

           // start success page
           Intent intent = new Intent(this, ScrollSuccess.class);
           startActivity(intent);

       return false;
   }