CALayers never calls it's delegate's drawLayer:inContext: even after [layer setNeedsDisplay] and [layer display]

calayer, core-animation, core-graphics, ios, objective-c

Solution

The layer frame needs to be non-zero. This solved the problem:

layer.frame = self.bg.bounds;
[layer setNeedsDisplay];
[self.bg.layer addSublayer:layer];

Problem

I can't figure out why the CALayer's I'm creating are not calling their drawLayer method. I've created a drawLayer delegate object for them, yet it never gets called. From a UIView subclass: ``` - (id)initWithFrame:(CGRect)frame { self = [super initWithFrame:frame]; if (self) { UIView *bg = [[UIView alloc] initWithFrame:self.bounds]; // I have a property called 'bg' to reference the child UIView self.bg = bg; [self addSubview:self.bg]; // an NSObject subclass I use as a CALayer delegate MyLayerDelegate *drawer = [MyLayerDelegate new]; self.drawer = drawer; CAGradientLayer *layer = [CAGradientLayer layer];; layer.delegate = self.drawer; layer.name = @"bg"; [self.bg.layer addSublayer:layer]; [layer setNeedsDisplay]; [layer display]; } return self; } ``` In self.drawer I have: ``` - (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)context { NSLog(@"layer called drawLayer"); // Some drawing goes here } ``` I've tried many different things. I've tried setting setNeedsDisplay on self.bg.layer, I've tried setNeedsDisplay on self.bg, I've tried [layer setNeedsDisplay] before AND after addSublayer, I've tried [layer display] before and after addSublayer. I've tried with and without [layer display] and [layer displayIfNeeded]. Why does the layer refuse to draw?

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