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()
    }
}

我还有一招。假设您有5个类，其中要应用注销警报。尝试使用swift类扩展。

文件-新建- Swift类-命名。

增加如下内容:

public extension UIViewController
{

    func makeLogOutAlert()
    {
        var refreshAlert = UIAlertController(title: "Log Out", message: "Are You Sure to Log Out ? ", preferredStyle: UIAlertControllerStyle.Alert)

        refreshAlert.addAction(UIAlertAction(title: "Confirm", style: .Default, handler: { (action: UIAlertAction!) in
            self.navigationController?.popToRootViewControllerAnimated(true)
        }))

        refreshAlert.addAction(UIAlertAction(title: "Cancel", style: .Default, handler: { (action: UIAlertAction!) in
            refreshAlert .dismissViewControllerAnimated(true, completion: nil)
        }))

        presentViewController(refreshAlert, animated: true, completion: nil)
    }
}

实现使用:self.makeLogOutAlert()。希望能有所帮助。

如果你的目标是iOS 7和8，你需要这样的东西来确保你对每个版本都使用了正确的方法，因为UIAlertView在iOS 8中已弃用，但UIAlertController在iOS 7中不可用:

func alert(title: String, message: String) {
    if let getModernAlert: AnyClass = NSClassFromString("UIAlertController") { // iOS 8
        let myAlert: UIAlertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
        myAlert.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))
        self.presentViewController(myAlert, animated: true, completion: nil)
    } else { // iOS 7
        let alert: UIAlertView = UIAlertView()
        alert.delegate = self

        alert.title = title
        alert.message = message
        alert.addButtonWithTitle("OK")

        alert.show()
    }
}

对于SWIFT4，我认为扩展UIViewController并创建一个可重用的确认控件是最优雅的方式。

你可以像下面这样扩展UIViewController:

extension UIViewController {

func AskConfirmation (title:String, message:String, completion:@escaping (_ result:Bool) -> Void) {
    let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
    self.present(alert, animated: true, completion: nil)

    alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: { action in
        completion(true)
    }))

    alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: { action in
        completion(false)
    }))
  }
}

那么你可以随时使用它:

 AskConfirmation(title: "YOUR MESSAGE TITLE", message: "YOUR MESSAGE") { (result) in
        if result { //User has clicked on Ok

        } else { //User has clicked on Cancel

        }
    }

从UIAlertView类:

// UIAlertView已弃用。使用UIAlertController 将UIAlertControllerStyleAlert改为preferredStyle

在iOS 8上，你可以这样做:

let alert = UIAlertController(title: "Alert", message: "Message", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Click", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)

UIAlertController是一个单独的类，用于创建和交互我们在ios8中知道的UIAlertViews和UIActionSheets。

编辑:处理动作:

alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: { action in
    switch action.style{
    case .Default:
        print("default")
        
    case .Cancel:
        print("cancel")
        
    case .Destructive:
        print("destructive")
    }
}}))

为Swift 3编辑:

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

为Swift 4.x编辑:

let alert = UIAlertController(title: "Alert", message: "Message", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { action in
    switch action.style{
        case .default:
        print("default")
        
        case .cancel:
        print("cancel")
        
        case .destructive:
        print("destructive")
        
    }
}))
self.present(alert, animated: true, completion: nil)

在Swift 4.2和Xcode 10中

方法一:

简单的提醒

let alert = UIAlertController(title: "Your title", message: "Your message", preferredStyle: .alert)
    
     let ok = UIAlertAction(title: "OK", style: .default, handler: { action in
     })
     alert.addAction(ok)
     let cancel = UIAlertAction(title: "Cancel", style: .default, handler: { action in
     })
     alert.addAction(cancel)
     DispatchQueue.main.async(execute: {
        self.present(alert, animated: true)
})

方法二:

使用共享类的警报

如果你想要共享类风格(写一次，随处使用)

import UIKit
class SharedClass: NSObject {//This is shared class
static let sharedInstance = SharedClass()

    //Show alert
    func alert(view: UIViewController, title: String, message: String) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        let defaultAction = UIAlertAction(title: "OK", style: .default, handler: { action in
        })
        alert.addAction(defaultAction)
        DispatchQueue.main.async(execute: {
            view.present(alert, animated: true)
        })
    }

    private override init() {
    }
}

现在每个软件都调用这样的警报

SharedClass.sharedInstance.alert(view: self, title: "Your title here", message: "Your message here")

方法三:

显示所有窗口的警告顶部

如果您想在所有视图的顶部显示警报，请使用以下代码

func alertWindow(title: String, message: String) {
    DispatchQueue.main.async(execute: {
        let alertWindow = UIWindow(frame: UIScreen.main.bounds)
        alertWindow.rootViewController = UIViewController()
        alertWindow.windowLevel = UIWindowLevelAlert + 1
    
        let alert2 = UIAlertController(title: title, message: message, preferredStyle: .alert)
        let defaultAction2 = UIAlertAction(title: "OK", style: .default, handler: { action in
        })
        alert2.addAction(defaultAction2)
    
        alertWindow.makeKeyAndVisible()
    
        alertWindow.rootViewController?.present(alert2, animated: true, completion: nil)
    })
}

函数调用

SharedClass.sharedInstance.alertWindow(title:"This your title", message:"This is your message")

方法四:

带扩展的警报

extension  UIViewController {

    func showAlert(withTitle title: String, withMessage message:String) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        let ok = UIAlertAction(title: "OK", style: .default, handler: { action in
        })
        let cancel = UIAlertAction(title: "Cancel", style: .default, handler: { action in
        })
        alert.addAction(ok)
        alert.addAction(cancel)
        DispatchQueue.main.async(execute: {
            self.present(alert, animated: true)
        })
    }
}

现在像这样调用

//Call showAlert function in your class
@IBAction func onClickAlert(_ sender: UIButton) {
    showAlert(withTitle:"Your Title Here", withMessage: "YourCustomMessageHere")
}

方法五:

带有文本字段的警报

如果你想添加文本框提醒。

//Global variables
var name:String?
var login:String?

//Call this function like this:  alertWithTF() 
//Add textfields to alert 
func alertWithTF() {
    
    let alert = UIAlertController(title: "Login", message: "Enter username&password", preferredStyle: .alert)
    // Login button
    let loginAction = UIAlertAction(title: "Login", style: .default, handler: { (action) -> Void in
        // Get TextFields text
        let usernameTxt = alert.textFields![0]
        let passwordTxt = alert.textFields![1]
        //Asign textfileds text to our global varibles
        self.name = usernameTxt.text
        self.login = passwordTxt.text
        
        print("USERNAME: \(self.name!)\nPASSWORD: \(self.login!)")
    })
    
    // Cancel button
    let cancel = UIAlertAction(title: "Cancel", style: .destructive, handler: { (action) -> Void in })
    
    //1 textField for username
    alert.addTextField { (textField: UITextField) in
        textField.placeholder = "Enter username"
        //If required mention keyboard type, delegates, text sixe and font etc...
        //EX:
        textField.keyboardType = .default
    }
    
    //2nd textField for password
    alert.addTextField { (textField: UITextField) in
        textField.placeholder = "Enter password"
        textField.isSecureTextEntry = true
    }
    
    // Add actions
    alert.addAction(loginAction)
    alert.addAction(cancel)
    self.present(alert, animated: true, completion: nil)
    
}

方法6:

带扩展的共享类中的警报

//This is your shared class
import UIKit

 class SharedClass: NSObject {

 static let sharedInstance = SharedClass()

 //Here write your code....

 private override init() {
 }
}

//Alert function in shared class
extension UIViewController {
    func showAlert(title: String, msg: String) {
        DispatchQueue.main.async {
            let alert = UIAlertController(title: title, message: msg, preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
            self.present(alert, animated: true, completion: nil)
        }
    }
}

现在像这样直接调用

self.showAlert(title: "Your title here...", msg: "Your message here...")

方法7:

警报与共享类与扩展在单独的类警报。

创建一个新的Swift类，并导入UIKit。复制并粘贴下面的代码。

//This is your Swift new class file
import UIKit
import Foundation

extension UIAlertController {
    class func alert(title:String, msg:String, target: UIViewController) {
        let alert = UIAlertController(title: title, message: msg, preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default) {
        (result: UIAlertAction) -> Void in
        })
        target.present(alert, animated: true, completion: nil)
    }
}

现在在你所有的类中调用alert函数(单行)。

UIAlertController.alert(title:"Title", msg:"Message", target: self)

怎么样....