控制器view的背景图片的方法, 四种：

1.直接在控制器view上添加一个imageView大小设置的和view一样

UIImageView *beijingimage = [UIImageView alloc]initWithImage:[UIImage imageNamed:@"beijing"];

beijingimage.frame = self.view.frame;

[self.view addSubview:beijingimage];

2.重写控制器view, 直接drawRect画在上面

UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, NO, 0);

UIImage * image = [UIImage imageNamed:@"beijing"];

[image drawAsPatternInRect:self.view.bounds];

3.把image转换成UIColor对象, 再通过设置背景颜色设置

self.view.backgroundColor = [UIColor colorWithPatternImage:@"beijing"];

4.设置layer.contents, 直接设置图片内容

self.view.layer.contents =[UIImage imageNamed:@"beijing"];