What does postInvalidate() do?

Question

What is the use of the postInvalidate() function in Android? I have been seeing this function in a lot of places. When I Googled, I came out with this much:

Answer 1

By this method (postInvalidate()), you can invalidate a View from non-UI threads. To invalidate a View from UI-thread use invalidate() method.

The invalidation means, that the View.onDraw(Canvas) method will we called at some point in the future (not immediately) to redraw whole View (if the View is visible).

Android is redrawing Views automaticly, but sometimes is necessary to tell: "Hey, this View has been changed, redraw it as fast as possible."

More at:

http://developer.android.com/guide/topics/ui/how-android-draws.html

http://developer.android.com/reference/android/view/View.html#invalidate%28%29