ios - 用复合 CALayer 遮罩 CALayer？

Question

我有一个主层，它有一个遮罩层。

遮罩层也有子层（在不同的遮罩形状中改变布局）。

但是遮罩子层对实际遮罩没有影响。:(

我可以用遮罩层做些什么吗？我想在动画中使用它，所以性能也是一个重点。

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蒙版层一开始是全白的，然后我放入较小的黑色/灰度内容，我只想看看结果。我可以用灰度图像屏蔽 CALayer 吗？

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// Disable layer actions with this delegate object.
self.layerDelegate = [TCLayerDelegate new];

// Create.
CALayer *layer = [CALayer layer];
layer.delegate = self.layerDelegate;

// Setup.
layer.contents = (id)self.colorImage.CGImage; // A simple opaque image with a color.
layer.frame = (CGRect){CGPointZero, self.size};
layer.anchorPoint = (CGPoint){ 0.0, 0.5 };

// Align.
self.layer.position = self.a;

// Create mask.
self.maskLayer = [CALayer layer];
self.maskLayer.delegate = self.layerDelegate;

// Setup.
self.maskLayer.contents = (id)self.maskImage.CGImage; // A black opaque image for now.
self.maskLayer.frame = (CGRect){CGPointZero, self.size};

// Add mask.
self.layer.mask = self.maskLayer;

// Add circles.
[self.circle createLayer]; // This object amongst many other things creates a transparent layer that holds a white circle.

// Add to mask.
[self.maskLayer addSublayer:self.circle.layer];

// Now I'd like to see layer masked with the circle.