ios - 带有 CAShapeLayer 蒙版的 CAGradientLayer 未显示

Question

我有以下代码:

- (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];
}

但它什么也没显示。不确定我遗漏了什么(除了我的图形)。

(faucet 和 faucetPath 都是属性)

更新

好的，我想 CAGradientLayer 必须有一个有意义的 frame。我假设 CAShapeLayer 的 frame 没有那么有意义，因为 path 可以超出 frame。添加以下行使其显示出来:

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

所以现在我的问题是，有没有办法避免必须这样做？我只是希望层的框架隐含地成为包含 View /层的框架。

Answer 1

您需要设置图层的边框。以下代码将绘制一个红色圆圈:

- (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];
}