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
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....
其他回答
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!")
}
}
iOS 13 Xcode 11+ Swift 5。X
UIAlertController现在可以提供警报以及动作表
警报
// First instantiate the UIAlertController
let alert = UIAlertController(title: "Title",
message: "Message ?",
preferredStyle: .alert)
// Add action buttons to it and attach handler functions if you want to
alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
alert.addAction(UIAlertAction(title: "Just Do It!", style: .destructive, handler: nil))
alert.addAction(UIAlertAction(title: "Maybe", style: .default, handler: nil))
// Show the alert by presenting it
self.present(alert, animated: true)
请注意，当点击警报视图时，所有操作按钮的基本属性都是关闭警报视图。style参数只是用来决定文本的颜色(以及按钮应该出现的默认顺序，这些ofc可以改变)
示例处理程序函数可以是
func handler(_ action: UIAlertAction) {
if action.title == 'Title' {
// do stuff
}
}
作为旁注，我想说的是，与其创建3个不同的处理程序，你可以只创建1个处理程序，并以上面所示的方式跟踪到引发它的元素 我们也可以检查警报。我们可以有多个。default样式的动作，我不建议这样做
动作表
解释是类似的，因为这里的主要区别是提醒会打断用户，而在iPhone中，操作表从底部滑动，在iPad中以弹出窗口的形式出现
操作表的目的是指导用户根据当前状态决定操作。所以你必须像对待十字路口一样对待动作表单!通常没有消息，标题呈现为标题大小的文本
let action = UIAlertController(title: "What do you want to do with the message",
message: nil,
preferredStyle: .actionSheet)
action.addAction(UIAlertAction(title: "Cancel", style: .cancel))
for act in ["Save", "Post", "Discard"] {
action.addAction(UIAlertAction(title: act, style: .default, handler: nil))
}
self.present(action, animated: true)
上面的代码将在iPhone上工作，但在iPad上运行时会崩溃，因为UIPopoverPresentationController将负责警报，它不会在那个时候引用任何东西。因此，为了避免这种情况，您必须提供以下代码块，这是强制性的
if let pop = action.popoverPresentationController {
let v = sender as! UIView
pop.sourceView = v
pop.sourceRect = v.bounds
}
同样，如果iPad点击弹窗之外的任何地方，它将被解散，.cancel操作按钮的完成处理程序将被调用。
也就是说，如果你有任何疑问，请在下方评论
不要在构造函数中提供otherbuttontitle。
let alertView = UIAlertView(title: "Oops!", message: "Something
happened...", delegate: nil, cancelButtonTitle: "OK")
alertView.show()
但我同意Oscar的观点，这个类在iOS 8中被弃用了，所以如果你只做iOS 8的应用程序，UIAlertView不会没有任何用途。否则上面的代码将工作。
一个按钮
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)
}
}
两个按钮
class ViewController: UIViewController {
@IBAction func showAlertButtonTapped(_ sender: UIButton) {
// create the alert
let alert = UIAlertController(title: "UIAlertController", message: "Would you like to continue learning how to use iOS alerts?", preferredStyle: UIAlertController.Style.alert)
// add the actions (buttons)
alert.addAction(UIAlertAction(title: "Continue", style: UIAlertAction.Style.default, handler: nil))
alert.addAction(UIAlertAction(title: "Cancel", style: UIAlertAction.Style.cancel, handler: nil))
// show the alert
self.present(alert, animated: true, completion: nil)
}
}
三个按钮
class ViewController: UIViewController {
@IBAction func showAlertButtonTapped(_ sender: UIButton) {
// create the alert
let alert = UIAlertController(title: "Notice", message: "Lauching this missile will destroy the entire universe. Is this what you intended to do?", preferredStyle: UIAlertController.Style.alert)
// add the actions (buttons)
alert.addAction(UIAlertAction(title: "Remind Me Tomorrow", style: UIAlertAction.Style.default, handler: nil))
alert.addAction(UIAlertAction(title: "Cancel", style: UIAlertAction.Style.cancel, handler: nil))
alert.addAction(UIAlertAction(title: "Launch the Missile", style: UIAlertAction.Style.destructive, handler: nil))
// show the alert
self.present(alert, animated: true, completion: nil)
}
}
处理按钮
在上面的例子中，处理程序为nil。当用户点击按钮时，你可以用一个闭包来替换nil。例如:
alert.addAction(UIAlertAction(title: "Launch the Missile", style: UIAlertAction.Style.destructive, handler: { action in
// do something like...
self.launchMissile()
}))
笔记
多个按钮不一定需要使用不同的UIAlertAction。风格类型。它们都可以是。default。 对于超过三个按钮，可以考虑使用动作表。设置非常相似。这里有一个例子。
点击查看
@IBAction func testClick(sender: UIButton) {
var uiAlert = UIAlertController(title: "Title", message: "Message", preferredStyle: UIAlertControllerStyle.Alert)
self.presentViewController(uiAlert, animated: true, completion: nil)
uiAlert.addAction(UIAlertAction(title: "Ok", style: .Default, handler: { action in
println("Click of default button")
}))
uiAlert.addAction(UIAlertAction(title: "Cancel", style: .Cancel, handler: { action in
println("Click of cancel button")
}))
}
完成两个按钮确定&取消
