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我有一个带有 UIImageView (imageView) 的 UIViewController，并且我在 viewDidLoad 中定义了几个将嵌套在 imageview 中的层，如下所示：

//container layer - the very top layer
CALayer *containerLayer = [CALayer layer];
containerLayer.opacity = 0;
containerLayer.bounds = [self.imageView.layer frame];

// Holder Layer
CALayer *holderLayer = [CALayer layer];
holderLayer.opacity = 0;
holderLayer.bounds = self.imageView.bounds;

// Hierarchy layers
[containerLayer setValue:holderLayer forKey:@"__holderLayer"];
[containerLayer addSublayer:holderLayer];

[self.imageView.layer addSublayer:containerLayer];

从 UIImagePicker 加载图像时，我有以下代码有效：

    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
    UIImageView *newImgView = [[UIImageView alloc] initWithFrame:self.imageView.frame];

    CGRect frame = self.imageView.frame;

    newImgView.image = image;
    frame.origin = CGPointMake(0, 0);
    newImgView.layer.frame = frame;
    newImgView.layer.opacity = .9;
    newImgView.layer.contentsGravity = kCAGravityResizeAspectFill;

    CALayer * containerLayer = self.imageView.layer.sublayers[0];

    if (containerLayer != nil)
    {

        [containerLayer setValue:newImgView.layer forKey:@"__imageLayer"];


        CALayer * holderLayer = [containerLayer valueForKey:@"__holderLayer"];
        if (holderLayer != nil)
        {
            //!!!!!line below doesn't work!!!
            //[holderLayer addSublayer:newImgView.layer];

            //line below works!
            [self.imageView.layer addSublayer:newImgView.layer];
        }   
    }
    [self.imageView setNeedsDisplay];
    [self checkAndPrintLayers];

所以第一个嵌套层是containerLayer，然后是holderLayer，我期望将各种图像作为子层添加到holderLayer，然后对其进行操作。然而，调用

  [holderLayer addSublayer:newImgView.layer];

不工作；imageView 保持空白。然而，调用

[self.imageView.layer addSublayer:newImgView.layer];

并在顶层添加一个子层只是花花公子。我在这里遗漏了一些明显的东西吗？希望有任何建议。谢谢。

4

1 回答 1

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因为

holderLayer 和 containerLayer 是透明的 (holderLayer.opacity = 0 / containerLayer.opacity = 0) ,

做了，

 //container layer - the very top layer
CALayer *containerLayer = [CALayer layer];
containerLayer.opacity = 1.0;
containerLayer.bounds = [self.imageView.layer frame];

// Holder Layer
CALayer *holderLayer = [CALayer layer];
holderLayer.opacity = 1.0;
holderLayer.bounds = self.imageView.bounds;
于 2013-05-08T19:26:01.073 回答