onAttachedToWindow () 和 onDetachedFromWindow ()

 

protected void onAttachedToWindow()

 This is called when the view is attached to a window. At this point it has a Surface and will start drawing. Note that this function is guaranteed to be called before onDraw(android.graphics.Canvas), however it may be called any time before the first onDraw -- including before or after onMeasure(int, int).

See Also

• onDetachedFromWindow()

如果你在自己的view中Override了这个方法。那么我们最关注的是它什么时候调用？

从开发文档中我们可以看出，onAttachedToWindow是在第一次onDraw前调用的。也就是我们写的View在没有绘制出来时调用的，但只会调用一次。

比如，我们写状态栏中的时钟的View，在onAttachedToWindow这方法中做初始化工作，比如注册一些广播等等……

 

 

与onAttachedToWindow 相反的则是这个方法：

 

protected void onDetachedFromWindow()

Since: API Level 1

This is called when the view is detached from a window. At this point it no longer has a surface for drawing.

See Also

• onAttachedToWindow()

开发文档就简单的两句。也就是我们销毁View的时候。我们写的这个View不再显示。

这时我们就在这个方法做一些收尾工作，如：取消广播注册等等。