ios - Swift 中的 UIAlert 会自动消失吗？

Question

我有以下代码:

    /// Creates Alerts on screen for user.
func notifyUser(title: String, message: String) -> Void
{
    let alert = UIAlertController(title: title,
        message: message,
        preferredStyle: UIAlertControllerStyle.Alert)

    let cancelAction = UIAlertAction(title: "OK",
        style: .Cancel, handler: nil)

    alert.addAction(cancelAction)
    UIApplication.sharedApplication().keyWindow?.rootViewController!.presentViewController(alert, animated: true,
        completion: nil)
}

其中显示以下警报:

我希望警报出现 1-2 秒后自动关闭，而无需单击“确定”或关闭。这可能吗？

Answer 1

是的，这是完全可能的，我认为@Duncan C 方法会很好地工作并且它是不言自明的，所以我将在代码中向您解释@Duncan 方法，另一种方法是使用 Grand Central Dispatch 的延迟(GCD)。

First Approach: Using the NSTimer class

// set the UIAlerController property
var alert: UIAlertController!

func notifyUser(title: String, message: String, timeToDissapear: Int) -> Void
{
    alert = UIAlertController(title: title,
        message: message,
        preferredStyle: UIAlertControllerStyle.Alert)

    let cancelAction = UIAlertAction(title: "OK",
        style: .Cancel, handler: nil)

    alert.addAction(cancelAction)
    UIApplication.sharedApplication().keyWindow?.rootViewController!.presentViewController(alert, animated: true,
        completion: nil)

    // setting the NSTimer to close the alert after timeToDissapear seconds.
    _ = NSTimer.scheduledTimerWithTimeInterval(Double(timeToDissapear), target: self, selector: Selector("dismissAlert"), userInfo: nil, repeats: false)
}

Second Approach: Using GCD

// set the UIAlerController property
var alert: UIAlertController! 

func notifyUser(title: String, message: String, timeToDissapear: Int) -> Void
{
    alert = UIAlertController(title: title,
        message: message,
        preferredStyle: UIAlertControllerStyle.Alert)

    let cancelAction = UIAlertAction(title: "OK",
        style: .Cancel, handler: nil)

    alert.addAction(cancelAction)
    UIApplication.sharedApplication().keyWindow?.rootViewController!.presentViewController(alert, animated: true,
        completion: nil)

    // Delay the dismissal by timeToDissapear seconds
    let delay = Double(timeToDissapear) * Double(NSEC_PER_SEC)
    let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
    dispatch_after(time, dispatch_get_main_queue()) { [weak self] in
        self!.alert.dismissViewControllerAnimated(true, completion: nil)
    }
}

然后您可以通过以下方式在任何您想要的地方调用它:

self.notifyUser("Hello", message: "World", timeToDissapear: 3)

希望对你有帮助