问题
I have seen many posts about this problem but didn't get an answer. I have a controller which view is added to the main window. The controller's view has a subview which has a drawRect. The problem is that this function is never called even if I call [self setNeedsDisplay].
Thanks
回答1:
It is -(void)drawRect:(CGRect)rect right? Make sure the method signature is correct, and you don't omit the rect argument even if you don't use it.
-setNeedsDisplay should be called the the subview, not self.
Also, -setNeedsDisplay won't call -drawRect: immediately. It only flushes the graphics cache so that -drawRect: is forced to be called in the next update of the frame.
来源：https://stackoverflow.com/questions/2744857/iphone-setneedsdisplay-doesnt-call-drawrect