Objective C - Unwanted black background behind circle - objective-c

Question

I'm trying to draw a green circle using drawRect but I'm getting a black background in the rectangle area around the green circle.
I need bounding rectangle's fill to be transparent.
Here my DrawCircle class:
- (void)drawRect:(CGRect)rect {
UIBezierPath *ballBezierPath = [UIBezierPath rect];
[[UIColor greenColor] setFill];
[ballBezierPath stroke];
self.opaque = NO;
self.backgroundColor = [UIColor clearColor];
}
My research indicated that adding the last two lines for setting opaque and backgroundColor would fix the issue, but it still doesn't work.
Here's where I'm adding the sub view in my ViewController's viewDidLoad method:
CGRect positionFrame = CGRectMake(160,160,200,200);
DrawCircle *drawBallView = [[DrawCircle alloc] initWithFrame:positionFrame];
[view1 addSubview:drawBallView];
Have I missed something or is there a different approach I can take?

Answer 1

There are a few problems with your current approach:
the properties are set too late, after you are actually drawing
you are setting those properties on each draw now, they only need to be set once
changing properties could trigger a redraw, and you'll end up redrawing over and over
you are overwriting drawRect: without a call to super. To make the backgroundColor work to either fill the rectangle yourself with that color, or have the superclass do it.
Move your view configuration to the initializers, drawRect is not a good to do any of that. Implement initWithFrame and initWithCoder (to support Interface Builder.
- (id) initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
[self setupView];
}
return self;
}
- (id) initWithCoder:(NSCoder *)aDecoder {
self = [super initWithCoder:aDecoder];
if (self) {
[self setupView];
}
return self;
}
- (void) setupView {
self.opaque = NO;
self.backgroundColor = [UIColor clearColor];
}