Question

我想在UIAlertController中使用viewDidAppear()显示提醒屏幕并等到按下该按钮（iOS 11）。

当前显示UIAlertController时，警告屏幕会在viewDidAppear()中调用，但不会显示，也无法点按此屏幕。

异步或延迟执行的警报屏幕。警报屏幕显示没有任何问题。

有没有什么好方法可以同步？

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    var doneloop = false

    let alert = UIAlertController(title:"Title", message: "Message", preferredStyle: UIAlertControllerStyle.alert)

    let action1 = UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: {
    (action: UIAlertAction!) in
       print("push OK button")

       doneloop = true // Runloop flag
    })

    alert.addAction(action1)

    self.present(alert, animated: false, completion: nil)

    while !doneloop {
       RunLoop.current.run(until: Date(timeIntervalSinceNow: 0.1))
    }

    alert.dismiss(animated: false, completion: nil)
}

Answer 1

我创建了这个方法，只需将完成处理所需的数据传递给此函数.....

//Alert with handling
func showMessageWithAction(_ messageText:String, messageTitle:String, okButtonTitle:String, cancelButtonTitle:String?, vc: UIViewController, completion:@escaping (Bool) -> Void) {

    let attribute = NSMutableAttributedString.init(string: messageText)
    attribute.addAttribute(NSAttributedStringKey.foregroundColor, value: UIColor.white , range: NSRange(location: 0,length: messageText.count))

    let alert = UIAlertController(title: messageTitle,
                                  message: messageText,
                                  preferredStyle: 
UIAlertControllerStyle.alert)
    alert.view.tintColor = UIColor(red: (0/255.0), green: (29/255.0), blue: (97/255.0), alpha: 1.0)
    alert.addAction(UIAlertAction(title: okButtonTitle,
                                  style: UIAlertActionStyle.default,
                                  handler: {(alert: UIAlertAction!) in
                                    completion(true)
    }))
    if let cancelButton = cancelButtonTitle {
        alert.addAction(UIAlertAction(title: cancelButton,
                                      style: UIAlertActionStyle.cancel,
                                      handler: {(alert: UIAlertAction!) in
                                        completion(false)
        }))
    }
    vc.present(alert, animated: true, completion: nil)
}

Answer 2

你这样做的方式相当混乱，没有必要同步它。

另外，我建议您在viewWillAppear而不是viewDidAppear中运行提醒演示文稿，以防您在每次进入此UIViewController后都看到提醒。

如果您想要运行一次，请使用viewDidLoad

我已在UIAlertController周围创建了一个包装器。

struct AlertWrapper {
    static func presentAlert(for vc: UIViewController, with title: String, message: String, dismissAlertAction: UIAlertAction? = nil, applyAlertAction: UIAlertAction? = nil) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        if dismissAlertAction != nil {
            alert.addAction(dismissAlertAction!)
        }
        if applyAlertAction != nil {
            alert.addAction(applyAlertAction!)
        }
        vc.present(alert, animated: true, completion: nil)
    }
}

上述方法中的示例

let applyAction = UIAlertAction(title: "Ok", style: .default) { (_) in
    // What ever you would like to do after pressing 'Ok'
}

let dismissAction = UIAlertAction(title: "Cancel", style: .default) { (_) in
    // What ever you would like to do after pressing 'Cancel'
}

AlertWrapper.presentAlert(for: self, with: "YOUR TITTLE", message: "YOUR MESSAGE", dismissAlertAction: dismissAction, applyAlertAction: applyAction)

可以随意提出任何问题，下次请阅读规则。

Example solution

Answer 3

简单方法

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    let alert = UIAlertController(title:"Title", message: "Message", preferredStyle: UIAlertControllerStyle.alert)
    let action1 = UIAlertAction(title: "OK", style: UIAlertActionStyle.default)
    alert.addAction(action1)
    self.present(alert, animated: false, completion: nil)
}

如何在viewDidAppear（）中同步UIAlert

3 个答案: