【android】说说GestureDetector.OnGestureListener onScroll函数

最新推荐文章于 2024-11-15 20:42:50 发布

原创最新推荐文章于 2024-11-15 20:42:50 发布 · 8.3k 阅读

2 ·

CC 4.0 BY-SA版权

文章标签：

#android #distance #scroll #float #api #null

android 专栏收录该内容

2 篇文章

订阅专栏

本文深入解析了滚动事件处理函数 onScroll 的用法，包括参数解释和返回值含义，通过实例验证了滚动距离的计算方式。

public abstract boolean onScroll (MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)

Since: API Level 1

Notified when a scroll occurs with the initial on down MotionEvent and the current move MotionEvent. The distance in x and y is also supplied for convenience.

Parameters

e1	The first down motion event that started the scrolling.
e2	The move motion event that triggered the current onScroll.
distanceX	The distance along the X axis that has been scrolled since the last call to onScroll. This is NOT the distance between `e1` and `e2`.
distanceY	The distance along the Y axis that has been scrolled since the last call to onScroll. This is NOT the distance between `e1` and `e2`.

Returns

true if the event is consumed, else false

e1 初次触控地图的event1

e2 每次触发onScroll函数得到的的event2

distance是上一次的event2 减去当前event2得到的结果 //注意到顺序

lastEvent2 - event2 = distance

验证：

if (lastE2 != null){
    Log.i(TAG, "distanceX:" + distanceX + " = " + (lastE2.getX()-e2.getX()));
    Log.i(TAG, "distanceY:" + distanceY + " = " + (lastE2.getY()-e2.getY()));
}
lastE2 = MotionEvent.obtain(e2);