Draw partially transparent UIView while using the backgroundColor

I'm creating a custom UIControl that renders it's view via drawRect:. I want to use the existing backgro开发者_JAVA百科undColor property to permit customization via Interface Builder. However, if the backgroundColor is set, by the time drawRect: is called, the entire rectangle has already been filled in. I have opaque = NO and clearsContextBeforeDrawing = YES. If I set the backgroundColor to clearColor then I can render only the parts that I want.

How do I prevent the UIView from filling in the entire rectangle with the backgroundColor automatically?

I should mention that the custom control is placed in Interface Builder so the initWithCoder: method is being used to instantiate the object.

This should certainly possible as if you inherit from UIButton - which uses the backgroundColor - the rectangle has not been filled in.

You need to overide:

- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx;

This is where the background color is applied. If you want the view to handle the background color, call the super's drawLayer method.

Since this is a custom control, could you add a variable UIColor *myColor, and, in the init method, after it has been read from the nib, set myColor = self.backgroundColor, and self.backgroundColor = [UIColor clearColor]? Then obviously use myColor in your drawRect.

I haven't tried this, and it seems a bit ugly, but maybe it works?