Android---Gesture手勢識別（一）

前言

這次主要講解一些Android簡單手勢的識別，主要用到的是GestureDetector，SimpleOnGestureListener，OnGestureListener等類

實現原理

我們想要實現手勢的識別，當然要監聽觸摸屏事件，主要流程是：重寫View的onTouchEvent事件，將攔截到的MotionEvent事件交給GestureDetector類的OnGestureListener和OnDoubleTapListener處理。我們可以分別處理OnGestureListener和OnDoubleTapListener中的事件，因爲我們不會用到所有的事件，所以我們也可以直接使用GestureDetector.SimpleOnGestureListener，這是一個實現了OnGestureListener接口和OnDoubleTapListener接口的類。

攔截事件

如果我們要攔截整個Activity的觸摸屏事件，重寫onTouchEvent（MotionEvent event）即可，當然我們可以爲單獨的 View設置監聽事件，view.setOnTouchListener，爲View添加監聽事件，然後將MotionEvent事件分發給GestureDetector處理mGestureDetector.onTouchEvent(event);

處理事件

SimpleOnGestureListener中的事件：

boolean onDoubleTap(MotionEvent e)
// Notified when a double-tap occurs.

boolean onDoubleTapEvent(MotionEvent e)
//Notified when an event within a double-tap gestureoccurs, including the down, move, and up events.

boolean onDown(MotionEvent e)
// Notified when a tap occurs with the down MotionEvent that triggered it.

boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
// Notified of a fling event when it occurs with the initial on down MotionEvent and the matching up MotionEvent.

void    onLongPress(MotionEvent e)
//Notified when a long press occurs with the initial on down MotionEvent that trigged it.

boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)
//Notified when a scroll occurs with the initial on down MotionEvent and the current move MotionEvent.

void    onShowPress(MotionEvent e)
//The user has performed a down MotionEvent and not performed a move or up yet.

boolean onSingleTapConfirmed(MotionEvent e)
// Notified when a single-tap occurs.

boolean onSingleTapUp(MotionEvent e)
// Notified when a tap occurs with the up MotionEvent that triggered it.

英語太渣，不給你們翻譯了 - -。

示例代碼

GestureDetector mGestureDetector;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init();
    }
    private void init()
    {
        mGestureDetector = new GestureDetector(this, new MyGestureListener());
    }
    @Override
    public boolean onTouchEvent(MotionEvent event)
    {
        return mGestureDetector.onTouchEvent(event);
    }
    class MyGestureListener extends SimpleOnGestureListener
    {
        @Override
        public boolean onDoubleTap(MotionEvent e)
        {
            Toast.makeText(MainActivity.this, "onDoubleTap", Toast.LENGTH_SHORT).show();
            return super.onDoubleTap(e);
        }
        @Override
        public boolean onDoubleTapEvent(MotionEvent e)
        {
            Toast.makeText(MainActivity.this, "onDoubleTapEvent", Toast.LENGTH_SHORT).show();
            return super.onDoubleTapEvent(e);
        }
        @Override
        public boolean onDown(MotionEvent e)
        {
            Toast.makeText(MainActivity.this, "onDown", Toast.LENGTH_SHORT).show();
            return super.onDown(e);
        }
        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                float velocityY)
        {
            Toast.makeText(MainActivity.this, "onFling", Toast.LENGTH_SHORT).show();
            if (e1.getX() - e2.getX() > 50)
            {
                Toast.makeText(MainActivity.this, "從右向左劃", Toast.LENGTH_SHORT)
                        .show();
            } else if (e2.getX() - e1.getX() > 50)
            {
                Toast.makeText(MainActivity.this, "從左向右劃", Toast.LENGTH_SHORT)
                        .show();
            }
            return super.onFling(e1, e2, velocityX, velocityY);
        }
        @Override
        public void onLongPress(MotionEvent e)
        {
            Toast.makeText(MainActivity.this, "onLongPress", Toast.LENGTH_SHORT).show();
            super.onLongPress(e);
        }
        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2,
                float distanceX, float distanceY)
        {
            Toast.makeText(MainActivity.this, "onScroll", Toast.LENGTH_SHORT).show();
            return super.onScroll(e1, e2, distanceX, distanceY);
        }
        @Override
        public void onShowPress(MotionEvent e)
        {
            Toast.makeText(MainActivity.this, "onShowPress", Toast.LENGTH_SHORT).show();
            super.onShowPress(e);
        }
        @Override
        public boolean onSingleTapConfirmed(MotionEvent e)
        {
            Toast.makeText(MainActivity.this, "onSingleTapConfirmed", Toast.LENGTH_SHORT).show();
            return super.onSingleTapConfirmed(e);
        }
        @Override
        public boolean onSingleTapUp(MotionEvent e)
        {
            Toast.makeText(MainActivity.this, "onSingleTapUp", Toast.LENGTH_SHORT).show();
            return super.onSingleTapUp(e);
        }
    }

這是簡單手勢的識別，下一篇講解一下自定義的手勢識別。
下篇：自定義手勢識別