android 手勢操作GestureDetector

利用觸摸屏的Fling、Scroll等Gesture（手勢）操作來操作會使得應用程序的用戶體驗大大提升，比如用Scroll手勢在 瀏覽器中滾屏，用Fling在閱讀器中翻頁等。在Android系統中，手勢的識別是通過 GestureDetector.OnGestureListener接口來實現的，舉例說明：

 

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);
        //構造GestureDetector;Context context, OnGestureListener listener
        detector = new GestureDetector(this, this);

        detector.setOnDoubleTapListener(new GestureDetector.OnDoubleTapListener() {
           //短快的點擊算一次單擊
            @Override
            public boolean onSingleTapConfirmed(MotionEvent e) {
                System.out.println("onSingleTapConfirmed");
                return false;
            }
            //雙擊時產生一次
            @Override
            public boolean onDoubleTap(MotionEvent e) {
                System.out.println("onDoubleTap");
                return false;
            }
          //雙擊時產生兩次
            @Override
            public boolean onDoubleTapEvent(MotionEvent e) {
                System.out.println("onDoubleTapEvent");
                return false;
            }
        });
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        return detector.onTouchEvent(event);
    }
    // 用戶輕觸觸摸屏，由1個MotionEvent ACTION_DOWN觸發
    @Override
    public boolean onDown(MotionEvent e) {
        System.out.println("onDown");
        return false;
    }
  // 用戶輕觸觸摸屏，尚未鬆開或拖動，由一個1個MotionEvent ACTION_DOWN觸發
   // 注意和onDown()的區別，強調的是沒有鬆開或者拖動的狀態
    @Override
    public void onShowPress(MotionEvent e) {

    }
    //用戶（輕觸觸摸屏後）鬆開，由一個1個MotionEvent ACTION_UP觸發
    @Override
    public boolean onSingleTapUp(MotionEvent e) {
        System.out.println("onSingleTapUp");
        return false;
    }
   // 用戶按下觸摸屏，並拖動，由1個MotionEvent ACTION_DOWN, 多個ACTION_MOVE觸發
    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        System.out.println("onScroll");
        return false;
    }
   // 用戶長按觸摸屏，由多個MotionEvent ACTION_DOWN觸發
    @Override
    public void onLongPress(MotionEvent e) {
        System.out.println("onLongPress" + e.getEventTime());
    }
   //用戶按下觸摸屏、快速移動後鬆開，由1個MotionEvent ACTION_DOWN, 多個ACTION_MOVE, 1個ACTION_UP觸發
    @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;
    }
}