CALayer新建图层

1、知识点梳理

+1. 添加图层：

• 例如：在View上添加新图层

[self.view.layer addSublayer:layer];

• 2.设置图层的内容, layer的属性contents -> id类型，要强转
  • 设置新图层的内容为一种图片

layer.contents = (id)[UIImage imageNamed:@"阿狸头像"].CGImage;
```

2、实例：在控制器的View上添加一个新的图层

#import "ViewController.h"
@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // 创建图层
    CALayer *layer = [CALayer layer];
    
    layer.backgroundColor = [UIColor redColor].CGColor;
   
    layer.frame = CGRectMake(0, 0, 100, 100);
    
    layer.contents = (id)[UIImage imageNamed:@"阿狸头像"].CGImage;
   
    [self.view.layer addSublayer:layer];
}