问题
In my swift app I have a UIViewController with a single button.
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")
})
}
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?
回答1:
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)")
}
}
回答2:
Just in case someone needs it, this is a Swift 4 version of the @Paulw11 solution
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)")
}
}
回答3:
I know this directly doesn't answer your question, but have you considered using MBProgressHUD SCLAlertView? They both offer functions that allow you to display an alert that disappears after a set amount of time. SCLAlertView allows the user to cancel immediately where as MBProgressHUD does not. If you want more info on how to implement these, let me know so I can add more info!
来源：https://stackoverflow.com/questions/36727474/how-can-i-display-a-popup-message-in-swift-that-disappears-after-3-seconds-or-ca