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。

UIAlertView可能就是你要找的。这里有一个例子:

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"No network connection" 
                                                message:@"You must be connected to the internet to use this app." 
                                               delegate:nil 
                                      cancelButtonTitle:@"OK"
                                      otherButtonTitles:nil];
[alert show];
[alert release];

如果你想做一些更有趣的事情，比如在UIAlertView中显示一个自定义UI，你可以子类化UIAlertView并在init方法中放入自定义UI组件。如果你想在UIAlertView出现后对按钮按下做出响应，你可以设置上面的委托并实现- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex方法。

你可能还想看看UIActionSheet。

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) {


}

下面是Xamarin.iOS中的c#版本

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

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。