参考(cocoachina):iOS-Core-Animation-Advanced-Techniques

简述

由于对view添加圆角需要maskToBounds = YES;而阴影正好是bounds之外渲染的,所以对同一个layer层添加显示圆角就不能显示阴影,参考以上文章,发现简单的方法就是对view添加自定义的layer从而实现圆角和需要圆角显示的图形, 然后再添加一个layer层用来显示阴影

实现代码如下:

//对self.loginBtn添加圆角,背景图片bkgImage, 以及阴影
    CALayer *sublayer =[CALayer layer];
    sublayer.backgroundColor =[UIColor whiteColor].CGColor;
    sublayer.shadowOffset = CGSizeMake(3, 10);
    sublayer.shadowRadius =22;
    sublayer.shadowColor =[UIColor blackColor].CGColor;
    sublayer.shadowOpacity =0.5;
    sublayer.frame = self.loginBtn.bounds;
    sublayer.cornerRadius =22;
    [self.loginBtn.layer addSublayer:sublayer];
    
    CALayer *imageLayer =[CALayer layer];
    imageLayer.frame = sublayer.bounds;
    imageLayer.cornerRadius =self.loginBtn.bounds.size.height / 2;
    imageLayer.contents =(id)backImage.CGImage;
    imageLayer.masksToBounds =YES;
    [sublayer addSublayer:imageLayer];