android 手势操作GestureDetector

利用触摸屏的Fling、Scroll等Gesture（手势）操作来操作会使得应用程序的用户体验大大提升，比如用Scroll手势在 浏览器中滚屏，用Fling在阅读器中翻页等。在Android 系统中，手势的识别是通过 GestureDetector.OnGestureListener接口来实现的，举例说明：

 

public class ActivityMain extends Activity implements GestureDetector.OnGestureListener {

    GestureDetector detector;

    /**
     * Called when the activity is first created.
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //构造GestureDetector;Context context, OnGestureListener listener
        detector = new GestureDetector(this, this);

        detector.setOnDoubleTapListener(new GestureDetector.OnDoubleTapListener() {
 //短快的点击算一次单击
            @Override
            public boolean onSingleTapConfirmed(MotionEvent e) {
                System.out.println("onSingleTapConfirmed");
                return false;
            }
 //双击时产生一次
            @Override
            public boolean onDoubleTap(MotionEvent e) {
                System.out.println("onDoubleTap");
                return false;
            }
  //双击时产生两次
            @Override
            public boolean onDoubleTapEvent(MotionEvent e) {
                System.out.println("onDoubleTapEvent");
                return false;
            }
        });
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        return detector.onTouchEvent(event);
    }
 // 用户轻触触摸屏，由1个MotionEvent ACTION_DOWN触发
    @Override
    public boolean onDown(MotionEvent e) {
        System.out.println("onDown");
        return false;
    }
 // 用户轻触触摸屏，尚未松开或拖动，由一个1个MotionEvent ACTION_DOWN触发
 // 注意和onDown()的区别，强调的是没有松开或者拖动的状态
    @Override
    public void onShowPress(MotionEvent e) {

    }
 //用户（轻触触摸屏后）松开，由一个1个MotionEvent ACTION_UP触发
    @Override
    public boolean onSingleTapUp(MotionEvent e) {
        System.out.println("onSingleTapUp");
        return false;
    }
 // 用户按下触摸屏，并拖动，由1个MotionEvent ACTION_DOWN, 多个ACTION_MOVE触发
    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        System.out.println("onScroll");
        return false;
    }
 // 用户长按触摸屏，由多个MotionEvent ACTION_DOWN触发
    @Override
    public void onLongPress(MotionEvent e) {
        System.out.println("onLongPress" + e.getEventTime());
    }
 //用户按下触摸屏、快速移动后松开，由1个MotionEvent ACTION_DOWN, 多个ACTION_MOVE, 1个ACTION_UP触发
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        System.out.println("onFling: " + (e1.getX() - e2.getX()) + " " + (e1.getY() - e2.getY()) + " " + velocityX + " " + velocityY);
        System.out.println(e1.getY());
        return false;
    }
}