如何在 Swift 中显示 3 秒后消失或可由用户立即取消的弹出消息? [英] How can I display a popup message in Swift that disappears after 3 seconds or can be cancelled by user immediatelly?

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.

In my swift app I have a UIViewController with a single button.

此按钮调用一个函数，该函数调用一个弹出窗口，该弹出窗口在 3 秒后消失.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:

This button invokes a function that calls a popup that disappears after 3 seconds. Also, after that time it prints a message to the console. The code of this function is as follows:

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")
    })

}

效果很好，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消息.有没有办法向用户显示这样的弹出窗口?另外 - 是否有一种方法可以在此弹出消息中显示已用完秒数的计数器，以显示在弹出窗口消失之前还剩下多少时间?

That works fine, but I wanted to introduce some improvement. I wanted to add there a button that will cancel this popup immediately and then avoid displaying the message in the console. Is there a way of displaying such popup to the user? Also - is there a way of showing in this popup message the counter with number of seconds running out that shows how much time is left until the popup disappears?

推荐答案

您可以使用 NSTimer 递减计数器，更新警报视图并在计数器达到 0 时关闭警报视图.这代码改编自我的 目标-C 答案

You can use an NSTimer to decrement a counter, update the alert view and dismiss the alert view when the counter reaches 0. This code is adapted from my 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)")
    }     
}

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