在ViewGroup类中，有这两个方法：
|
|
Call this method to remove all child views from the ViewGroup.从ViewGroup中移除所有子视图
|
|
|
Called by a ViewGroup subclass to remove child views from itself,
when it must first know its size on screen before it can calculate how many child views it will render.
ViewGroup的子类调用，移除自身的子视图，但在它能计算多少子视图被渲染前，必须首先知道它在屏幕中尺寸。
|
所以在有些情况下，removeAllViews()能移除掉子视图，但removeAllviewsInLayout()移除不掉，因为子视图还未计算。