自iOS 8发布以来，UIAlertView现在已弃用;UIAlertController是替换的。

下面是它在Swift 5中的示例:

let alert = UIAlertController(title: "Hello!", message: "Message", preferredStyle: .alert)
let alertAction = UIAlertAction(title: "OK!", style: .default) { (sender: UIAlertAction) -> Void in
    // ... Maybe handle "OK!" being tapped.
}
alert.addAction(alertAction)

// Show.
present(alert, animated: true) { () -> Void in
    // ... Maybe do something once showing is complete.
}

如您所见，API允许我们实现对动作和呈现警报时的回调，这非常方便!

对于较旧的Swift版本:

let alert = UIAlertController(title: "Hello!", message: "Message", preferredStyle: UIAlertControllerStyle.alert)
let alertAction = UIAlertAction(title: "OK!", style: UIAlertActionStyle.default)
{
    (UIAlertAction) -> Void in
}
alert.addAction(alertAction)
present(alert, animated: true)
{
    () -> Void in
}

对于Swift 3和Swift 4:

由于UIAlertView已弃用，所以在Swift 3上有一个显示Alert的好方法

let alertController = UIAlertController(title: NSLocalizedString("No network connection",comment:""), message: NSLocalizedString("connected to the internet to use this app.",comment:""), preferredStyle: .alert)
let defaultAction = UIAlertAction(title:     NSLocalizedString("Ok", comment: ""), style: .default, handler: { (pAlert) in
                //Do whatever you want here
        })
alertController.addAction(defaultAction)
self.present(alertController, animated: true, completion: nil)

弃用:

这是受选中响应启发的swift版本:

显示AlertView:

   let alert = UIAlertView(title: "No network connection", 
                           message: "You must be connected to the internet to use this app.", delegate: nil, cancelButtonTitle: "Ok")
    alert.delegate = self
    alert.show()

将委托添加到视图控制器:

class AgendaViewController: UIViewController, UIAlertViewDelegate

当用户点击按钮，这段代码将被执行:

func alertView(alertView: UIAlertView, clickedButtonAtIndex buttonIndex: Int) {


}

虽然我已经写了不同类型的弹出窗口的概述，但大多数人只需要一个警报。

如何实现弹出对话框

class ViewController: UIViewController {

    @IBAction func showAlertButtonTapped(_ sender: UIButton) {

        // create the alert
        let alert = UIAlertController(title: "My Title", message: "This is my message.", preferredStyle: UIAlertController.Style.alert)

        // add an action (button)
        alert.addAction(UIAlertAction(title: "OK", style: UIAlertAction.Style.default, handler: nil))

        // show the alert
        self.present(alert, animated: true, completion: nil)
    }
}

我更完整的答案在这里。

从iOS 8.0开始，你需要像下面这样使用UIAlertController:

-(void)alertMessage:(NSString*)message
{
    UIAlertController* alert = [UIAlertController
          alertControllerWithTitle:@"Alert"
          message:message
          preferredStyle:UIAlertControllerStyleAlert];

    UIAlertAction* defaultAction = [UIAlertAction 
          actionWithTitle:@"OK" style:UIAlertActionStyleDefault
         handler:^(UIAlertAction * action) {}];

    [alert addAction:defaultAction];
    [self presentViewController:alert animated:YES completion:nil];
}
  

self在我的例子中是一个UIViewController，它为弹出窗口实现了presentViewController方法。

自iOS 8发布以来，UIAlertView现在已弃用;UIAlertController是替换的。

下面是它在Swift 5中的示例:

let alert = UIAlertController(title: "Hello!", message: "Message", preferredStyle: .alert)
let alertAction = UIAlertAction(title: "OK!", style: .default) { (sender: UIAlertAction) -> Void in
    // ... Maybe handle "OK!" being tapped.
}
alert.addAction(alertAction)

// Show.
present(alert, animated: true) { () -> Void in
    // ... Maybe do something once showing is complete.
}

如您所见，API允许我们实现对动作和呈现警报时的回调，这非常方便!

对于较旧的Swift版本:

let alert = UIAlertController(title: "Hello!", message: "Message", preferredStyle: UIAlertControllerStyle.alert)
let alertAction = UIAlertAction(title: "OK!", style: UIAlertActionStyle.default)
{
    (UIAlertAction) -> Void in
}
alert.addAction(alertAction)
present(alert, animated: true)
{
    () -> Void in
}

下面是Xamarin.iOS中的c#版本

var alert = new UIAlertView("Title - Hey!", "Message - Hello iOS!", null, "Ok");
alert.Show();