// UIAlertView is deprecated. Use UIAlertController 
  // title = title of the alert view.
  // message = Alert message you want to show.
  // By tap on "OK" , Alert view will dismiss.

 UIAlertView(title: "Alert", message: "Enter Message here.", delegate: nil, cancelButtonTitle: "OK").show()

使用此代码显示alertview

  let alertController = UIAlertController(title: "Hello  Coders", message: "your alert message", preferredStyle: .Alert)
        let defaultAction = UIAlertAction(title: "Close Alert", style: .Default, handler: nil)
        alertController.addAction(defaultAction)

        presentViewController(alertController, animated: true, completion: nil)

Swift显示警报使用UIAlertController

适用于13.0以上版本 使用SceneDelegate

适用于所有类型的课程

static func showWindowAlert(alertMessage: String, inVC:UIViewController) {
        DispatchQueue.main.async(execute: {
            guard let windowScene = UIApplication.shared.connectedScenes.first as? UIWindowScene,
                let sceneDelegate = windowScene.delegate as? SceneDelegate
              else {
                return
              }
            sceneDelegate.window?.rootViewController = inVC
            sceneDelegate.window?.windowLevel = UIWindow.Level.alert + 1
        
            let alert2 = UIAlertController(title: App_Name, message: alertMessage, preferredStyle: .alert)
            let defaultAction2 = UIAlertAction(title: "OK", style: .default, handler: { action in
            })
            alert2.addAction(defaultAction2)
        
            sceneDelegate.window?.makeKeyAndVisible()
        
            sceneDelegate.window?.rootViewController?.present(alert2, animated: true, completion: nil)
        })
    }

我已经做了一个单例类，以便从应用程序的任何地方使用:https://github.com/Swinny1989/Swift-Popups

然后你可以创建一个带有多个按钮的弹出窗口，如下所示:

Popups.SharedInstance.ShowAlert(self, title: "Title goes here", message: "Messages goes here", buttons: ["button one" , "button two"]) { (buttonPressed) -> Void in
    if buttonPressed == "button one" { 
      //Code here
    } else if buttonPressed == "button two" {
        // Code here
    }
}

或者弹出一个按钮，像这样:

Popups.SharedInstance.ShowPopup("Title goes here", message: "Message goes here.")

// UIAlertView的自定义类

//MARK:- MODULES
import Foundation
import UIKit

//MARK:- CLASS
class Alert  : NSObject{

static let shared = Alert()

var okAction : AlertSuccess?
typealias AlertSuccess = (()->())?
var alert: UIAlertController?

/** show */
public func show(title : String?, message : String?, viewController : UIViewController?, okAction : AlertSuccess = nil) {

    let version : NSString = UIDevice.current.systemVersion as NSString
    if  version.doubleValue >= 8 {
        alert = UIAlertController(title: title, message: message, preferredStyle:.alert)
        alert?.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action: UIAlertAction) in

            if let okAction = okAction {
                okAction()
            }
        }))
        viewController?.present(alert ?? UIAlertController(), animated:true, completion:nil);
    }
}

/** showWithCancelAndOk */
public func showWithCancelAndOk(title : String, okTitle : String, cancelTitle : String, message : String, viewController : UIViewController?, okAction : AlertSuccess = nil, cancelAction : AlertSuccess = nil) {
    let version:NSString = UIDevice.current.systemVersion as NSString;

    if  version.doubleValue >= 8 {
        alert = UIAlertController(title: title, message: message, preferredStyle:.alert)

        alert?.addAction(UIAlertAction(title: cancelTitle, style: .default, handler: { (action: UIAlertAction) in

            if let cancelAction = cancelAction {
                cancelAction()
            }
        }))
        alert?.addAction(UIAlertAction(title: okTitle, style: .default, handler: { (action: UIAlertAction) in

            if let okAction = okAction {
                okAction()
            }
        }))
        viewController?.present(alert!, animated:true, completion:nil);
    }
}

/** showWithTimer */
public func showWithTimer(message : String?, viewController : UIViewController?) {

    let version : NSString = UIDevice.current.systemVersion as NSString
    if  version.doubleValue >= 8 {
        alert = UIAlertController(title: "", message: message, preferredStyle:.alert)
        viewController?.present(alert ?? UIAlertController(), animated:true, completion:nil)
        let when = DispatchTime.now() + 1
        DispatchQueue.main.asyncAfter(deadline: when){
            self.alert?.dismiss(animated: true, completion: nil)
        }
    }
}
}

使用:

Alert.shared.show(title: "No Internet Connection", message: "The internet connection appers to be offline.", viewController: self) //without ok action

Alert.shared.show(title: "No Internet Connection", message: "The internet connection appers to be offline.", viewController: self, okAction: {
                            //ok action
                        }) // with ok action

Alert.shared.show(title: "No Internet Connection", message: "The internet connection appers to be offline.", viewController: self, okAction: {
                            //ok action 
}, cancelAction: {
 //cancel action
}) //with cancel and ok action

Alert.shared.showWithTimer(message : "This is an alert with timer", viewController : self) //with timer

我得到了以下UIAlertView初始化代码编译没有错误(我认为最后，变量部分可能是棘手的)。但我必须确保类的自我(我传递的委托)采用UIAlertViewDelegate协议编译错误消失:

let alertView = UIAlertView(
                  title: "My Title",
                  message: "My Message",
                  delegate: self,
                  cancelButtonTitle: "Cancel",
                  otherButtonTitles: "OK"
                )

顺便说一下，这是我得到的错误(作为Xcode 6.4):

无法为类型“UIAlertView”找到接受参数的初始化式 类型为'的参数列表(标题:字符串，消息:字符串，委托: MyViewController, cancelButtonTitle: String, otherbuttontitle: 字符串)”

正如其他人提到的，如果你的目标是iOS 8.x+，你应该迁移到UIAlertController。要支持iOS 7，请使用上面的代码(Swift不支持iOS 6)。