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

In simple words, invalidate() method can be called from UI Thread and postInvalidate() can be called from non-UI Thread in order to tell android to update our Custom View after some changes are made to it.