UIWindow 功能在 Xcode11.3 中不起作用吗？

Question

我有这样的警报控制器代码。
但我尝试呈现警报，警报不显示给我。
对我有什么想法。
谢谢。

public extension UIAlertController {
    func show() {
        let win = UIWindow(frame: UIScreen.main.bounds)
        let vc = UIViewController()
        vc.view.backgroundColor = .clear
        win.rootViewController = vc
        win.windowLevel = UIWindow.Level.alert + 1
        win.makeKeyAndVisible()
        vc.present(self, animated: true, completion: nil)
    }
}


let alertController = UIAlertController(title: newTitle, message: newMessage, preferredStyle: .alert)

let submit = UIAlertAction(title: submitTitle, style: .default) { (action) in
                clickOK()
            }

alertController.addAction(submit)
if let cancelTitle = cancelTitle, !cancelTitle.isEmpty {
    let cancel = UIAlertAction(title: cancelTitle, style: .cancel) { (action) in
        if let clickCancel = clickCancel {
          clickCancel()
        }
    }
    alertController.addAction(cancel)
}

alertController.show()

Answer 1

似乎你需要持有 UIWindow 对象，直到你想显示警报这是工作代码，几乎没有变化

private var win: UIWindow!
extension UIAlertController {
    func show() {
        win = UIWindow(frame: UIScreen.main.bounds)
        let vc = UIViewController()
        vc.view.backgroundColor = .clear
        win.rootViewController = vc
        win.windowLevel = .alert + 1
        win.makeKeyAndVisible()
        win.rootViewController?.present(self, animated: true, completion: nil)
    }

    open override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        win = nil
    }
}

用法
使用方式与您之前使用的相同

let alertController = UIAlertController(title: newTitle, message: newMessage, preferredStyle: .alert)

let submit = UIAlertAction(title: submitTitle, style: .default) { (action) in
                clickOK()
            }

alertController.addAction(submit)
if let cancelTitle = cancelTitle, !cancelTitle.isEmpty {
    let cancel = UIAlertAction(title: cancelTitle, style: .cancel) { (action) in
        if let clickCancel = clickCancel {
          clickCancel()
        }
    }
    alertController.addAction(cancel)
}

alertController.show()

Answer 2

你也可以使用这个 swift 5.0 扩展

  public extension UIAlertController {

    func showAlert() {
    let window = UIWindow(frame: UIScreen.main.bounds)
    let vc = UIViewController()
    vc.view.backgroundColor = .clear
    window.rootViewController = vc
    window.windowLevel = UIWindow.Level.alert + 1  
    window.makeKeyAndVisible()    
    vc.present(self, animated: true, completion: nil)
}
}

使用标题和消息设置警报控制器并像这样调用

 alertObject.showAlert()