左右滑動事件

新增OnSwipeTouchListener.java

public abstract class OnSwipeTouchListener implements View.OnTouchListener {
    private final GestureDetector gestureDetector;
    public OnSwipeTouchListener (Context ctx){
        gestureDetector = new GestureDetector(ctx, new GestureListener());
    }
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        return gestureDetector.onTouchEvent(event);
    }
    private final class GestureListener extends GestureDetector.SimpleOnGestureListener {
        private static final int SWIPE_THRESHOLD = 100;
        private static final int SWIPE_VELOCITY_THRESHOLD = 100;
        @Override
        public boolean onDown(MotionEvent e) {
            return true;
        }
        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            boolean result = false;
            try {
                float diffY = e2.getY() - e1.getY();
                float diffX = e2.getX() - e1.getX();
                if (Math.abs(diffX) > Math.abs(diffY)) {
                    if (Math.abs(diffX) > SWIPE_THRESHOLD && 
                            Math.abs(velocityX) > SWIPE_VELOCITY_THRESHOLD) {
                        if (diffX > 0) {
                            onSwipeRight();
                        } else {
                            onSwipeLeft();
                        }
                    }
                    result = true;
                }
                else if (Math.abs(diffY) > SWIPE_THRESHOLD && 
                        Math.abs(velocityY) > SWIPE_VELOCITY_THRESHOLD) {
                    if (diffY > 0) {
                        onSwipeBottom();
                    } else {
                        onSwipeTop();
                    }
                }
                result = true;

            } catch (Exception exception) {
                exception.printStackTrace();
            }
            return result;
        }
    }
    abstract void onSwipeRight();
    abstract void onSwipeLeft();
    abstract void onSwipeTop();
    abstract void onSwipeBottom();
}

於各元件設定如下事件

imageView.setOnTouchListener(new OnSwipeTouchListener(this){
    public void onSwipeRight() {
        position=(position-1+Common.list.size())%Common.list.size();
        setImage();
    }
    public void onSwipeLeft() {
        position=(position+1)%Common.list.size();
        setImage();
    }
    @Override
    void onSwipeTop() {}
    @Override
    void onSwipeBottom() {}
});