如何在 Swift 中显示一条弹出消息，该消息在 3 秒后消失或可以由用户立即取消？

Posted 2023-02-23

【中文标题】如何在 Swift 中显示一条弹出消息，该消息在 3 秒后消失或可以由用户立即取消？

【英文标题】：How can I display a popup message in Swift that disappears after 3 seconds or can be cancelled by user immediatelly?

【发布时间】：2016-04-19 19:16:41

【问题描述】：

在我的 swift 应用程序中，我有一个带有单个按钮的 UIViewController。

此按钮调用一个函数，该函数调用一个 3 秒后消失的弹出窗口。此外，在那之后，它会向控制台打印一条消息。该函数的代码如下：

func showAlertMsg(title: String, message: String)


    let alertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
    self.presentViewController(alertController, animated: true, completion: nil)
    let delay = 3.0 * Double(NSEC_PER_SEC)
    let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
    dispatch_after(time, dispatch_get_main_queue(), 
        alertController.dismissViewControllerAnimated(true, completion: nil)
    print("popup disappeared")
    )

这很好，但我想介绍一些改进。我想在那里添加一个按钮，该按钮将立即取消此弹出窗口，然后避免在控制台中显示该消息。有没有办法向用户显示这样的弹出窗口？另外 - 有没有办法在这个弹出消息中显示秒数用完的计数器，显示在弹出窗口消失之前还剩多少时间？

【问题讨论】：

这是我在 Objectice C ***.com/questions/36048240/… 中写的类似答案。本质上，您需要使用 NSTimer 倒计时并在所需时间后关闭警报

这看起来很有希望，我不得不承认 :) 你有没有机会在 swift 中有一个 smilar 代码？我（还）不熟悉 obj-c :|

【参考方案1】：

您可以使用NSTimer 来减少计数器，更新警报视图并在计数器达到 0 时关闭警报视图。此代码改编自我的Objective-C answer

class ViewController: UIViewController 

    var alertController: UIAlertController?
    var alertTimer: NSTimer?
    var remainingTime = 0
    var baseMessage: String?

    override func viewDidLoad() 
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    

    override func viewDidAppear(animated: Bool) 
        super.viewDidAppear(animated)         
        self.showAlertMsg("Test Alert", message: "This will disappear in ", time: 5)
    

    override func didReceiveMemoryWarning() 
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    

    func showAlertMsg(title: String, message: String, time: Int) 

        guard (self.alertController == nil) else 
            print("Alert already displayed")
            return
        

        self.baseMessage = message
        self.remainingTime = time

        self.alertController = UIAlertController(title: title, message: self.alertMessage(), preferredStyle: .Alert)

        let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel)  (action) in
            print("Alert was cancelled")
            self.alertController=nil;
            self.alertTimer?.invalidate()
            self.alertTimer=nil
        

        self.alertController!.addAction(cancelAction)

        self.alertTimer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(ViewController.countDown), userInfo: nil, repeats: true)       

        self.presentViewController(self.alertController!, animated: true, completion: nil)     
    

    func countDown() 

        self.remainingTime -= 1
        if (self.remainingTime < 0) 
            self.alertTimer?.invalidate()
            self.alertTimer = nil
            self.alertController!.dismissViewControllerAnimated(true, completion: 
                self.alertController = nil
            )
         else 
            self.alertController!.message = self.alertMessage()
        

    

    func alertMessage() -> String 
        var message=""
        if let baseMessage=self.baseMessage 
            message=baseMessage+" "
        
        return(message+"\(self.remainingTime)")
         

【讨论】：

这里是更新的 Swift 3 代码的链接：gist.github.com/anonymous/aadd8e56f2049062c68458c477c28a34

【参考方案2】：

以防万一有人需要，这是@Paulw11 解决方案的 Swift 4 版本

import UIKit

class ViewController: UIViewController 

    var alertController: UIAlertController?
    var alertTimer: Timer?
    var remainingTime = 0
    var baseMessage: String?

    override func viewDidLoad() 
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    

    override func viewDidAppear(_ animated: Bool) 
        super.viewDidAppear(animated)
        self.showAlertMsg(title: "Test Alert", message: "This will disappear in ", time: 5)
    

    override func didReceiveMemoryWarning() 
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    

    func showAlertMsg(title: String, message: String, time: Int) 

        guard (self.alertController == nil) else 
            print("Alert already displayed")
            return
        

        self.baseMessage = message
        self.remainingTime = time

        self.alertController = UIAlertController(title: title, message: self.alertMessage(), preferredStyle: .alert)

        let cancelAction = UIAlertAction(title: "Cancel", style: .cancel)  (action) in
            print("Alert was cancelled")
            self.alertController=nil;
            self.alertTimer?.invalidate()
            self.alertTimer=nil
        

        self.alertController!.addAction(cancelAction)

        self.alertTimer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(ViewController.countDown), userInfo: nil, repeats: true)

        self.present(self.alertController!, animated: true, completion: nil)
    

    @objc func countDown() 

        self.remainingTime -= 1
        if (self.remainingTime < 0) 
            self.alertTimer?.invalidate()
            self.alertTimer = nil
            self.alertController!.dismiss(animated: true, completion: 
                self.alertController = nil
            )
         else 
            self.alertController!.message = self.alertMessage()
        

    

    func alertMessage() -> String 
        var message=""
        if let baseMessage=self.baseMessage 
            message=baseMessage+" "
        
        return(message+"\(self.remainingTime)")
    

【参考方案3】：

我知道这不能直接回答您的问题，但您是否考虑过使用MBProgressHUDSCLAlertView？它们都提供允许您显示在设定的时间后消失的警报的功能。 SCLAlertView 允许用户立即取消，而 MBProgressHUD 不允许。如果您想了解有关如何实施这些的更多信息，请告诉我，以便我添加更多信息！

【讨论】：

嘿@DanL，谢谢，SCLAlertView 看起来很有趣！但是 - 有没有办法显示在弹出窗口关闭之前还剩多少秒的计数器？

我不认为它内置在 SCLAlertView 中，但我看不出有什么理由不能创建一个 NSTimer 来显示给用户。如果您不知道如何创建倒数计时器，我会在网上快速查找倒数计时器。然后，当 SCLAlertView 出现时，您将触发计时器。请注意，如果您将警报设置为三秒，则计时器可能只会倒计时两秒或两秒半，因为加载需要一点时间。我只想玩弄计时器以使其正常工作。