带有CAShapeLayer遮罩的CAGradientLayer未显示

Question

I have the following code:

- (void)setupLayer {
    self.faucetShape = [CAShapeLayer layer];
    self.faucetShape.strokeColor = [[UIColor blackColor] CGColor];
    self.faucetShape.lineWidth = 2;
    self.faucetShape.fillColor = nil;
    self.faucetShape.path = [self faucetPath].CGPath; // faucetPath returns a 4 point diamond shaped UIBezierPath*
    self.faucet = [CAGradientLayer layer];
    self.faucet.mask = self.faucetShape;
    self.faucet.colors = @[(id)[UIColor redColor].CGColor, (id)[UIColor redColor].CGColor];
    [self.layer addSublayer: self.faucet];
}

But it shows nothing. Not sure what I'm missing (other than my graphic).

( faucet and faucetPath are both properties)

UPDATE

OK, I guess a CAGradientLayer has to have a meaningful frame . I assume a CAShapeLayer 's frame isn't as meaningful, since the path can go outside the frame . Adding the following line made it show up:

self.faucet.frame = CGRectMake(0, 0, 64, 64);

So NOW my question is, is there a way to avoid having to do that? I'd just like the frame of the layer to implicitly be that of the containing View/Layer.

Answer 1

You need to set the frame of the layers. The following code will draw a red circle:

- (void)setupLayer
{
    CAShapeLayer *faucetShape = [CAShapeLayer layer];
    faucetShape.frame = CGRectMake(0, 0, 100, 100);
    faucetShape.strokeColor = [[UIColor blackColor] CGColor];
    faucetShape.lineWidth = 2;
    faucetShape.fillColor = nil;
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddEllipseInRect(path, nil, CGRectMake(0, 0, 100, 100));
    faucetShape.path = path;
    CGPathRelease(path);
    CAGradientLayer *faucet = [CAGradientLayer layer];
    faucet.frame = CGRectMake(10, 10, 100, 100);
    faucet.mask = faucetShape;
    faucet.colors = @[(id)[UIColor redColor].CGColor, (id)[UIColor redColor].CGColor];
    [self.view.layer addSublayer: faucet];
}