CALayer won't display

Posted by Paul from Boston on Stack Overflow See other posts from Stack Overflow or by Paul from Boston
Published on 2010-03-24T19:49:25Z Indexed on 2010/03/24 19:53 UTC
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I'm trying to learn how to use CALayers for a project and am having trouble getting sublayers to display. I created a vanilla View-based iPhone app in XCode for these tests. The only real code is in the ViewController which sets up the layers and their delegates. There is a delegate, DelegateMainView, for the viewController's view layer and a second different one, DelegateStripeLayer, for an additional layer. The ViewController code is all in awakeFromNib,

- (void)awakeFromNib {

 DelegateMainView *oknDelegate = [[DelegateMainView alloc] init];
 self.view.layer.delegate = oknDelegate;

 CALayer *newLayer = [CALayer layer];
 DelegateStripeLayer *sldDelegate = [[DelegateStripeLayer alloc] init];
 newLayer.delegate = sldDelegate;

 [self.view.layer addSublayer:newLayer];

 [newLayer setNeedsDisplay];
 [self.view.layer setNeedsDisplay];

}

The two different delegates are simply wrappers for the CALayer delegate method, drawLayer:inContext:, i.e.,

- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)context {

 CGRect bounds = CGContextGetClipBoundingBox(context);
      ... do some stuff here ...
 CGContextStrokePath(context);     

}

each a bit different. The layer, view.layer, is drawn properly but newLayer is never drawn. If I put breakpoints in the two delegates, the program stops in DelegateMainView but never reaches DelegateStripeLayer. What am I missing here? Thanks.

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