模糊效果没有出现在UITableViewCell中

Question

我正在尝试为视图添加模糊效果。 我像这样创建了模糊效果

let blurLabel: UIVisualEffectView = {
    let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.dark)
    let blurEffectView = UIVisualEffectView(effect: blurEffect)


    return blurEffectView
    }()

然后像这样将其添加到子视图中，并设置约束

 override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
        super.init(style: .subtitle, reuseIdentifier: reuseIdentifier)
        let view = tableViewCell

        addSubview(view)
        view.addSubview(blurLabel)

 blurLabel.leftAnchor.constraint(equalTo: self.leftAnchor,constant:0).isActive = true
        //blurLabel.topAnchor.constraint(equalTo: self.topAnchor, constant: 178).isActive = true
        blurLabel.widthAnchor.constraint(equalToConstant: 375).isActive = true
        blurLabel.heightAnchor.constraint(equalToConstant: 180).isActive = true

但是当我运行该应用程序时，它根本没有出现

Answer 1

编辑：根据@HAS和@Fogmeister的建议，您也可以使用translatesAutoResizingMaskIntoConstraints = false因为这是使用自动布局而不指定显式框架的更好解决方案。

您必须像这样将框架分配给UIVisualEffectView ：

 let blurLabel: UIVisualEffectView = {
    let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.dark)
    let blurEffectView = UIVisualEffectView(effect: blurEffect)
    blurEffectView.frame = CGRect(x: 0, y: 0, width: 60, height: 40) //give desirable frame
    return blurEffectView
 }()

Answer 2

如果愿意，除了提供明确的框架外，还可以为任何视图或子视图提供blurView。

let blurLabel: UIVisualEffectView = {
    let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.dark)
    let blurEffectView = UIVisualEffectView(effect: blurEffect)    
    blurEffectView.frame = myMainview.bounds //Blur effect's frame
    return blurEffectView
}()

override func viewDidLoad() {
    super.viewDidLoad()
    // Use it somewhere using
    self.view.insertSubview(blurEffectView, belowSubview: myAnotherView)
    // You may also use any of the subviews too, instead of the self.view
    /// self.myView.insertSubview(blurEffectView, belowSubview: myAnotherView)
}

Answer 3

要解决此问题，只需停止自动创建约束即可。 像这样...

let blurLabel: UIVisualEffectView = {
    let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.dark)
    let blurEffectView = UIVisualEffectView(effect: blurEffect)
    // this line will stop constraints being added for a zero frame
    blurEffectView.translatesAutoResizingMaskIntoConstraints = false
    return blurEffectView
}()