iPhone - setNeedsDisplay doesn't call drawRect

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 prob开发者_运维问答lem is that this function is never called even if I call [self setNeedsDisplay].

Thanks

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.