How to determine moment when WebView (or View) ready to screenshot?

I have 开发者_运维知识库a problem, I need to make screenshots of WebView in different sizes at once (in portrait and lanscape) and make it fast.

So, to make a screenshot I change WebView's layout params, and call invalidate(), as you know it works asynchronously and will take effect at some moment later.

How can I determine moment when WebView applied new layout params and ready to make screenshot?