滑动手势监听类 GestureDetector.OnGestureListener

    /**
     * The listener that is used to notify when gestures occur.
     * If you want to listen for all the different gestures then implement
     * this interface. If you only want to listen for a subset it might
     * be easier to extend {@link SimpleOnGestureListener}.
     */
    public interface OnGestureListener {

        /**
         * Notified when a tap occurs with the down {@link MotionEvent}
         * that triggered it. This will be triggered immediately for
         * every down event. All other events should be preceded by this.
         *
         * @param e The down motion event.
         */
        boolean onDown(MotionEvent e);

        /**
         * The user has performed a down {@link MotionEvent} and not performed
         * a move or up yet. This event is commonly used to provide visual
         * feedback to the user to let them know that their action has been
         * recognized i.e. highlight an element.
         *
         * @param e The down motion event
         */
        void onShowPress(MotionEvent e);

        /**
         * Notified when a tap occurs with the up {@link MotionEvent}
         * that triggered it.
         *
         * @param e The up motion event that completed the first tap
         * @return true if the event is consumed, else false
         */
        boolean onSingleTapUp(MotionEvent e);

        /**
         * Notified when a scroll occurs with the initial on down {@link MotionEvent} and the
         * current move {@link MotionEvent}. The distance in x and y is also supplied for
         * convenience.
         *
         * @param e1 The first down motion event that started the scrolling.
         * @param e2 The move motion event that triggered the current onScroll.
         * @param distanceX The distance along the X axis that has been scrolled since the last
         *              call to onScroll. This is NOT the distance between {@code e1}
         *              and {@code e2}.
         * @param distanceY The distance along the Y axis that has been scrolled since the last
         *              call to onScroll. This is NOT the distance between {@code e1}
         *              and {@code e2}.
         * @return true if the event is consumed, else false
         */
        boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY);

        /**
         * Notified when a long press occurs with the initial on down {@link MotionEvent}
         * that trigged it.
         *
         * @param e The initial on down motion event that started the longpress.
         */
        void onLongPress(MotionEvent e);

        /**
         * Notified of a fling event when it occurs with the initial on down {@link MotionEvent}
         * and the matching up {@link MotionEvent}. The calculated velocity is supplied along
         * the x and y axis in pixels per second.
         *
         * @param e1 The first down motion event that started the fling.
         * @param e2 The move motion event that triggered the current onFling.
         * @param velocityX The velocity of this fling measured in pixels per second
         *              along the x axis.
         * @param velocityY The velocity of this fling measured in pixels per second
         *              along the y axis.
         * @return true if the event is consumed, else false
         */
        boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY);
    }