如何从UIAlertView迁移(在iOS8中已弃用)

Question

我目前在我的一个应用程序中有以下代码行.这很简单UIAlertView.但是,从iOS 8开始,现在不推荐使用它:

let alertView = UIAlertView(title: "Oops!", message: "This feature isn't available right now", delegate: self, cancelButtonTitle: "OK")

如何更新此功能以使用iOS 8+？我相信我必须改变一些东西UIAlertCotroller,虽然我不太清楚是什么.

Answer 1

你需要UIAlertController改用.为了类文档是非常简单的,甚至包含在文档的开始清单1中的使用实例(确保它在ObjC而不是斯威夫特但它是非常相似).

因此,对于您的用例,以下是它的转换方式(添加了注释):

let alert = UIAlertController(title: "Oops!", message:"This feature isn't available right now", preferredStyle: .alert)
let action = UIAlertAction(title: "OK", style: .default) { _ in
  // Put here any code that you would like to execute when
  // the user taps that OK button (may be empty in your case if that's just
  // an informative alert)
}
alert.addAction(action)
self.presentViewController(alert, animated: true){}

所以紧凑的代码看起来像:

let alert = UIAlertController(title: "Oops!", message:"This feature isn't available right now", preferredStyle: .Alert)
alert.addAction(UIAlertAction(title: "OK", style: .Default) { _ in })
self.present(alert, animated: true){}

凡self在这里应该是你的UIViewController.

附加提示:如果您需要调用UIViewController在self(不在其中UIViewController)的上下文之外显示警报的代码,您可以随时使用应用的根VC:

let rootVC = UIApplication.sharedApplication().keyWindow?.rootViewController
rootVC?.presentViewController(alert, animated: true){}

(但总的来说,UIViewController当你有一个已知的时候最好使用已知的- 并且你通常会提出来自UIViewControllers的警报 - 或者根据你的上下文尝试获得最合适的警报,而不是依赖于这个提示)

Answer 2

对于那些想知道如何在Objective-C中执行此操作的人:

    //Step 1: Create a UIAlertController
    UIAlertController *myAlertController = [UIAlertController alertControllerWithTitle:@"MyTitle"
                                                              message: @"MyMessage"
                                                              preferredStyle:UIAlertControllerStyleAlert                   ];

    //Step 2: Create a UIAlertAction that can be added to the alert
    UIAlertAction* ok = [UIAlertAction
                         actionWithTitle:@"OK"
                         style:UIAlertActionStyleDefault
                         handler:^(UIAlertAction * action)
                         {
                             //Do some thing here, eg dismiss the alertwindow
                             [myAlertController dismissViewControllerAnimated:YES completion:nil];

                         }];

    //Step 3: Add the UIAlertAction ok that we just created to our AlertController
    [myAlertController addAction: ok];

    //Step 4: Present the alert to the user
    [self presentViewController:myAlertController animated:YES completion:nil];

这将弹出一个如下所示的警报: