removeAllViews()和removeAllViewsInLayout()的区别

在ViewGroup类中，有这两个方法：
voidremoveAllViews()

Call this method to remove all child views from the ViewGroup.从ViewGroup中移除所有子视图

voidremoveAllViewsInLayout()

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。