ios给view设置背景颜色的正确方式

  UIView *back=[[UIView alloc]initWithFrame:CGRectMake(0, 0, WIDTH, HEIGHT)];

    UIImage *image=[UIImage imageNamed:@"background.jpg"];

    back.layer.contents=(__bridge id _Nullable)(image.CGImage);

    back.layer.backgroundColor=[UIColor clearColor].CGColor;

住：直接调用background方法，图片不会被拉伸，所以会导致图片显示异常