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Asked: 2026-05-12T08:00:18+00:00

How can I use both of these in the same UIView correctly? I have

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How can I use both of these in the same UIView correctly?

I have one custom subclassed CALayer in which I draw a pattern within drawInContext

I have a another in which I set an overlay PNG image as the contents.

I have a third which is just a background.

How do I overlay all 3 of these items?

[self.layer addSublayer:bottomLayer];    // this line is the problem

[squaresLayer drawInContext:viewContext];
[self.layer addSublayer:imgLayer];

The other 2 by themselves draw correctly if I do them in that order. No matter where I try and put bottomLayer, it always prevents squaresLayer from drawing. The reason I need 3 layers is I intend to animate the colors in the background and custom layers. The top layer is just a graphical overlay.

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1 Answer

  1. Editorial Team

    Might as well paste the code in in case anyone is trying to animate stacked CALayers that have their own internal draw routines

    - (void)drawRect:(CGRect)rect {

    [imgLayer removeFromSuperlayer];

    CGFloat w = [self.blockViewDelegate w];
    CGFloat h = [self.blockViewDelegate h];

    CGFloat wb = w/4;
    CGFloat hb = h/4;

    CGContextRef viewContext = UIGraphicsGetCurrentContext();

    // Layers

    [bottomLayer sizes:wb :hb :1];
    bottomLayer.frame = CGRectMake(0, 0, w, h);
    bottomLayer.opaque = NO;

    [topLayer sizes:wb :hb :0];
    topLayer.frame = CGRectMake(0, 0, w, h);
    topLayer.opaque = NO;

    // Overlay

    imgLayer.frame = CGRectMake(0, 0, w, h);
    imgLayer.opaque = NO;
    imgLayer.opacity = 1.0f;

    UIImage *overlay = [self.blockViewDelegate image];
    CGImageRef img = overlay.CGImage;
    imgLayer.contents = (id)img;

    // Add layers

    [bottomLayer drawInContext:viewContext];
    [topLayer drawInContext:viewContext];
    [self.layer addSublayer:imgLayer];

}

    blockViewDelegate is where I am storing width, height, and image information, it is the controller for this UIView.

    topLayer and bottomLayer are of a custom UIView subclass which draw some shapes in the view with variable color information. Later on in my animation I just run “setNeedsDisplay” repeatedly with a timer and this routine repeats, the layers re-draw using updated parameters.

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