view添加陰影無效

需求：需要給cell里的imageview添加陰影

問題：按照標准的代碼添加陰影，然並卵：代碼如下：

    imageview.layer.shadowColor = [[UIColor blackColor] CGColor];
    imageview.layer.shadowOffset = CGSizeMake(4.0f, 4.0f);
    imageview.layer.shadowRadius = 4.0;
    imageview.layer.shadowOpacity = 0.5;

后谷歌說要加一句：

imageview.layer.masksToBounds = NO;，因為陰影是在imagview的layer外面畫的

這樣陰影出來了，然而，由於允許子元素超出父元素，所以圖片的大小就不一樣了

 

因此歪果仁提出了一個辦法，創建兩層view，內層view是imageview，不允許超出邊界，外層view是shadowview，ref:

http://www.innofied.com/implementing-shadow-ios/(這個是為了解決圓角view＋陰影的問題)

代碼：

//注意這個layer一定添加在imageview被add后面
CALayer *sublayer = [[CALayer layer]initWithLayer:self.imageView.layer];

    UIView * shadow = [[UIView alloc] initWithFrame:self.imageView
                       .frame];
    shadow.userInteractionEnabled = NO; // Modify this if needed
    shadow.layer.shadowColor = [[UIColor blackColor] CGColor];
    shadow.layer.shadowOffset = CGSizeMake(4.0f, 4.0f);
    shadow.layer.shadowRadius = 4.0;
    shadow.layer.masksToBounds = NO;   //關鍵
    shadow.clipsToBounds = NO;
    shadow.layer.shadowOpacity = 0.5;
    [ self.imageView.superview insertSubview:shadow belowSubview: self.imageView];
    [shadow addSubview:self.imageView];