我一直在努力创建一个UIAlertView在Swift,但由于某种原因,我不能得到正确的声明,因为我得到这个错误:

无法找到一个超载的'init'接受提供的 参数

我是这样写的:

let button2Alert: UIAlertView = UIAlertView(title: "Title", message: "message",
                     delegate: self, cancelButtonTitle: "OK", otherButtonTitles: nil)

然后我使用:

button2Alert.show()

到目前为止,它正在崩溃,我只是不能得到正确的语法。


当前回答

你可以使用标准的构造函数创建一个UIAlert,但是“遗留的”构造函数似乎不起作用:

let alert = UIAlertView()
alert.title = "Alert"
alert.message = "Here's a message"
alert.addButtonWithTitle("Understood")
alert.show()

其他回答

Swift 5上的SwiftUI。x和Xcode 11.x

import SwiftUI

struct ContentView: View {

    @State private var isShowingAlert = false

    var body: some View {
        VStack {
            Button("A Button") {

                self.isShowingAlert.toggle()
            }
            .alert(isPresented: $isShowingAlert) { () -> Alert in
                Alert(
                    title: Text("Alert"),
                    message: Text("This is an alert"),
                    dismissButton:
                        .default(
                            Text("OK"),
                            action: {
                                print("Dismissing alert")
                            }
                        )
                )
            }

        }
        .padding()
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}
    class Preview: UIViewController , UIAlertViewDelegate
    {
        @IBAction func MoreBtnClicked(sender: AnyObject)
        {
            var moreAlert=UIAlertView(title: "Photo", message: "", delegate: self, cancelButtonTitle: "No Thanks!", otherButtonTitles: "Save Image", "Email", "Facebook", "Whatsapp" )
            moreAlert.show()
            moreAlert.tag=111;
        }

        func alertView(alertView: UIAlertView, didDismissWithButtonIndex buttonIndex: Int)
        {
            if alertView.tag==111
            {
                if buttonIndex==0
                {
                    println("No Thanks!")
                }
                else if buttonIndex==1
                {
                    println("Save Image")
                }
                else if buttonIndex == 2
                {
                    println("Email")
                }
                else if buttonIndex == 3
                {
                    println("Facebook")
                }
                else if buttonIndex == 4
                {
                    println("Whatsapp")
                }
            }
        }
    }

通过Swift 2的协议扩展,你可以创建一个为视图控制器提供默认实现的协议:

ShowsAlert.swift

import UIKit

protocol ShowsAlert {}

extension ShowsAlert where Self: UIViewController {
    func showAlert(title: String = "Error", message: String) {
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
        alertController.addAction(UIAlertAction(title: "Ok", style: .Default, handler: nil))
        presentViewController(alertController, animated: true, completion: nil)
    }
}

ViewController.swift

class ViewController: UIViewController, ShowsAlert {
    override func viewDidLoad() {
        super.viewDidLoad()
        showAlert(message: "Hey there, I am an error message!")
    }
}

在xcode 9中

let alert = UIAlertController(title: "Alert", message: "message", preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: nil))
self.present(alert, animated: true, completion: nil)

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