Swift - 告警提示框（UIAlertController）的用法

自iOS8起，苹果就建议告警框使用UIAlertController来代替UIAlertView和UIActionSheel。下面总结了一些常见的用法（ 本文代码都已更新至Swift3）

1，简单的应用（同时按钮响应Handler使用闭包函数）

  

import  UIKit

class  ViewController :  UIViewController  {
    override  func  viewDidLoad() {
        super .viewDidLoad()
    }

    override  func  viewDidAppear(_ animated:  Bool ){
        super .viewDidAppear(animated)

        let  alertController =  UIAlertController (title:  "系统提示" ,
                        message:  "您确定要离开hangge.com吗？" , preferredStyle: .alert)
        let  cancelAction =  UIAlertAction (title:  "取消" , style: .cancel, handler:  nil )
        let  okAction =  UIAlertAction (title:  "好的" , style: . default , handler: {
            action  in
            print ( "点击了确定" )
        })
        alertController.addAction(cancelAction)
        alertController.addAction(okAction)
        self .present(alertController, animated:  true , completion:  nil )
    }

    override  func  didReceiveMemoryWarning() {
        super .didReceiveMemoryWarning()
    }
}

2，除了弹出，还可以使用从底部向上滑出的样式
（注意：如果上拉菜单中有“取消”按钮的话，那么它永远都会出现在菜单的底部，不管添加的次序是如何）

 

let  alertController =  UIAlertController (title:  "保存或删除数据" , message:  "删除数据将不可恢复" ,
                                        preferredStyle: .actionSheet)
let  cancelAction =  UIAlertAction (title:  "取消" , style: .cancel, handler:  nil )
let  deleteAction =  UIAlertAction (title:  "删除" , style: .destructive, handler:  nil )
let  archiveAction =  UIAlertAction (title:  "保存" , style: . default , handler:  nil )
alertController.addAction(cancelAction)
alertController.addAction(deleteAction)
alertController.addAction(archiveAction)
self .present(alertController, animated:  true , completion:  nil )

3，按钮使用“告警”样式（文字颜色变红，用来来警示用户）

  

let  okAction =  UIAlertAction (title:  "好的" , style: .destructive, handler:  nil )

4，添加任意数量文本输入框（比如可以用来实现个登陆框）

  

import  UIKit

class  ViewController :  UIViewController  {
    override  func  viewDidLoad() {
        super .viewDidLoad()
    }

    override  func  viewDidAppear(_ animated:  Bool ){
        super .viewDidAppear(animated)

        let  alertController =  UIAlertController (title:  "系统登录" ,
                            message:  "请输入用户名和密码" , preferredStyle: .alert)
        alertController.addTextField {
            (textField:  UITextField !) ->  Void  in
            textField.placeholder =  "用户名"
        }
        alertController.addTextField {
            (textField:  UITextField !) ->  Void  in
            textField.placeholder =  "密码"
            textField.isSecureTextEntry =  true
        }
        let  cancelAction =  UIAlertAction (title:  "取消" , style: .cancel, handler:  nil )
        let  okAction =  UIAlertAction (title:  "好的" , style: . default , handler: {
            action  in
            //也可以用下标的形式获取textField let login = alertController.textFields![0]
            let  login = alertController.textFields!.first!
            let  password = alertController.textFields!.last!
            print ( "用户名：\(login.text) 密码：\(password.text)" )
        })
        alertController.addAction(cancelAction)
        alertController.addAction(okAction)
        self .present(alertController, animated:  true , completion:  nil )
    }

    override  func  didReceiveMemoryWarning() {
        super .didReceiveMemoryWarning()
    }
}

5，使用代码移除提示框

self .presentedViewController?.dismiss(animated:  false , completion:  nil )

6，提示框弹出后，过段时间自动移除
下面样例弹出一个不带按钮的消息提示框，过个两秒钟提示框自动消失。

let  alertController =  UIAlertController (title:  "保存成功!" ,
                                        message:  nil , preferredStyle: .alert)
//显示提示框
self .present(alertController, animated:  true , completion:  nil )
//两秒钟后自动消失
DispatchQueue .main.asyncAfter(deadline:  DispatchTime .now() + 2) {
    self .presentedViewController?.dismiss(animated:  false , completion:  nil )
}

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