Question

我有一个带有UIImageView（imageView）的UIViewController，我在viewDidLoad中定义了几个将嵌套在imageview中的图层：

//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];

我有以下代码在从UIImagePicker加载图像时有效：

    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，我希望将各种图像作为子层添加到holderLayer然后进行操作。但是，请致电

  [holderLayer addSublayer:newImgView.layer];

不起作用; imageView保持空白。但是，请致电

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

并在顶层添加子图层只是花花公子。我错过了一些明显的东西吗？会喜欢任何建议。感谢。

Answer 1

因为

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

制作它，

 //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;

CALayer从UIImagePicker加载图像时出现故障

1 个答案:

因为