CALayers基础概念入门_adc中layers的含义-优快云博客

本文链接：https://blog.youkuaiyun.com/nerohoop/article/details/7294237

本文介绍了如何使用UIKit和Core Animation定制iOS视图效果，包括设置背景颜色、圆角、阴影等样式，并展示了如何通过添加子图层实现更复杂的视觉效果。

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self.view.layer.backgroundColor = [UIColor orangeColor].CGColor;
self.view.layer.cornerRadius = 20.0;
self.view.layer.frame = CGRectInset(self.view.layer.frame, 20, 20);

CALayer *sublayer = [CALayer layer];
sublayer.backgroundColor = [UIColor blueColor].CGColor;
sublayer.shadowOffset = CGSizeMake(0, 3);
sublayer.shadowRadius = 5.0;
sublayer.shadowColor = [UIColor blackColor].CGColor;
sublayer.shadowOpacity = 0.8;
sublayer.frame = CGRectMake(30, 30, 128, 192);
[self.view.layer addSublayer:sublayer];

layer和视图一样可以添加子layer

sublayer.contents = (id) [UIImage imageNamed:@"BattleMapSplashScreen.jpg"].CGImage;
sublayer.borderColor = [UIColor blackColor].CGColor;
sublayer.borderWidth = 2.0;

CALayer *sublayer = [CALayer layer];
sublayer.backgroundColor = [UIColor blueColor].CGColor;
sublayer.shadowOffset = CGSizeMake(0, 3);
sublayer.shadowRadius = 5.0;
sublayer.shadowColor = [UIColor blackColor].CGColor;
sublayer.shadowOpacity = 0.8;
sublayer.frame = CGRectMake(30, 30, 128, 192);
sublayer.borderColor = [UIColor blackColor].CGColor;
sublayer.borderWidth = 2.0;
sublayer.cornerRadius = 10.0;
[self.view.layer addSublayer:sublayer];
 
CALayer *imageLayer = [CALayer layer];
imageLayer.frame = sublayer.bounds;
imageLayer.cornerRadius = 10.0;
imageLayer.contents = (id) [UIImage imageNamed:@"BattleMapSplashScreen.jpg"].CGImage;
imageLayer.masksToBounds = YES;
[sublayer addSublayer:imageLayer];

同时应用圆角和阴影

1.每个视图对象都一个Core Animation layer来管理和动画显示视图内容

2.当视图被创建之后，其layer的类型不能改变。如果需要改变其layer，则重载视图的方法

+ (Class)layerClass
{
    return [CAEAGLLayer class];
}

3.每个视图在初始化时调用其layerClass类方法，使用其返回对象来创建视图的layer。并且，视图将自身设置为layer的代理对象
4.添加layer到视图中

Listing 3-3  Adding a custom layer to a view
- (void)viewDidLoad {
    [super viewDidLoad];
 
    // Create the layer.
    CALayer* myLayer = [[CALayer alloc] init];
 
    // Set the contents of the layer to a fixed image. And set
    // the size of the layer to match the image size.
    UIImage layerContents = [[UIImage imageNamed:@"myImage"] retain];
    CGSize imageSize = layerContents.size;
 
    myLayer.bounds = CGRectMake(0, 0, imageSize.width, imageSize.height);
    myLayer = layerContents.CGImage;
 
    // Add the layer to the view.
    CALayer*    viewLayer = self.view.layer;
    [viewLayer addSublayer:myLayer];
 
    // Center the layer in the view.
    CGRect        viewBounds = backingView.bounds;
    myLayer.position = CGPointMake(CGRectGetMidX(viewBounds), CGRectGetMidY(viewBounds));
 
    // Release the layer, since it is retained by the view's layer
    [myLayer release];
}

5.自定义视图不会接受事件或参与响应链，但是会根据父视图或者父layer的大小进行改变