IOS添加底边框的方法

CALayer *bottomBorder = [CALayer layer];      float height=self.view.frame.size.height-1.0f;    float width=self.view.frame.size.width;    bottomBorder.frame = CGRectMake(0.0f, height, width, 1.0f);     bottomBorder.backgroundColor = [UIColor colorWithWhite:0.8f alpha:1.0f].CGColor;      [self.view.layer addSublayer:bottomBorder];