Question

I am having a wicked time trying to get an image to show up in a CALayer.contents. It seems rather straight forward but I cannot get the image to render no matter what I do. The CALayer renders fine as I can see its background color and corner radius, but the image will not load.

What you are seeing here is a CAGradientLayer subclass with a mask applied. The inner square is where I would like the image to show, and it is added as a sublayer of the CAGradientLayer subclass.

The code to set this up is pretty straightforward. In init:

self.imageLayer = [CALayer layer];
self.imageLayer.cornerRadius = kDefaultCornerRadius;
self.imageLayer.backgroundColor = [UIColor darkGrayColor].CGColor;
[self addSublayer:self.imageLayer];

Then later on, I set the image:

- (void)setImage:(UIImage *)image {
    self.imageLayer.contents = (id)image.CGImage;
    [self.imageLayer setNeedsDisplay];
}

Finally, within setFrame:

CGFloat imageSize = self.bounds.size.width - 2*kDefaultMargin;
[self.imageLayer setBounds:CGRectMake(0.0, 0.0, imageSize, imageSize)];
[self.imageLayer setPosition:CGPointMake(self.bounds.size.width/2.0f, kDefaultMargin + imageSize/2.0f)];
[self.imageLayer setNeedsDisplay];

Things I already know or have checked:

1. The layer is obviously added correctly evident by it being visible.
2. The image is added and works. [UIImage imageNamed:@"info.png"] is being used elsewhere in the code and actually shows and image. It is 16×16 at 1x and 32×32 at 2x
3. The code is being called in the correct logical order: init, setImage:, setFrame;

What is going on here?

Answer 1

Remove this line:

[self.imageLayer setNeedsDisplay];

-setNeedsDisplay tells a layer that it needs to redraw its contents. Since you already provided the content for the layer, you don’t want CA to discard that content and ask for a replacement.