简易贴背景图

若页面整页需要加背景图，传统做法如下:(123为图片名)

UIImageView *backImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, ScreenWidth, ScreenHeight)];
backImageView.image = [UIImage imageNamed:@"123"];
[self.view addSubview:backImageView];

get新技能：

self.view.layer.contents = (__bridge id _Nullable)([UIImage imageNamed:@"123"].CGImage);

哈哈。