使用一个view的getWidth() getHeight() 方法来获取该view的宽和高，返回的值却为0。如果这个view的长宽很确定不为0的话，那很可能是你过早的调用这些方法，也就是说在这个view被加入到rootview之前你就调用了这些方法，返回的值自然为0.

解决该问题的方法有很多，主要就是延后调用这些方法。可以试着在onWindowFocusChanged()里面调用这些方法。

以下是stack overflow中的回答。

Anyhow, the deal is that layout of the contents of a window happens after all the elements are constructed and added to their parent views. It has to be this way, because until you know what components a View contains, and what they contain, and so on, there's no sensible way you can lay it out.

Bottom line, if you call getWidth() etc. in a constructor, it will return zero. The procedure is to create all your view elements in the constructor, then wait for your View's onSizeChanged() method to be called -- that's when you first find out your real size, so that's when you set up the sizes of your GUI elements.

Be aware too that onSizeChanged() is sometimes called with parameters of zero -- check for this case, and return immediately (so you don't get a divide by zero when calculating your layout, etc.). Some time later it will be called with the real values.