UIAlertController 在 AppDelegate didFinishLaunchingWithOptions 方法中不起作用 - 在 Swift 中

Question

我试图在用户第一次下载应用程序时弹出一个 UIAlertController。但是，当我将代码放入 didFinishLaunchingWithOptions 时，出现以下错误，

2015-01-15 23:54:45.306 WeddingApp Warning: Attempt to present UIAlertController:  on UITabBarController: whose view is not in the window hierarchy!

我的代码如下：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

    // Override point for customization after application launch.
        if window == nil {
        println("window is nil");
        return true;
    }

    if window!.rootViewController == nil {
        println("window!.rootViewController is nil");
        return true;
    }

    //TabBarController//
    let tabBarController: UITabBarController = window!.rootViewController! as UITabBarController;
    UITabBar.appearance().tintColor = UIColor.magentaColor();
    UITabBar.appearance().translucent = false;

/* tableView cells are now completely visable. They do not hie behind the tabBar */

    tabBarController.viewControllers = [
        TwelveToTenMonths(nibName: nil, bundle:nil),
        NineToSevenMonths(nibName: nil, bundle:nil),
        SixToFourMonths(nibName: nil, bundle:nil),
        ThreeToOneMonth(nibName: nil, bundle:nil),
    ];



    var alert = UIAlertController(
                title: "Welcome to WeddingApp!",
                message: "Thank You for choosing the \nWedding App for your organization needs. \n\nFor more great tools please visit our website www.wedme.com",
                preferredStyle: UIAlertControllerStyle.Alert);

    alert.addAction(UIAlertAction(title: "Continue", style: UIAlertActionStyle.Default, handler: nil));

    self.window!.rootViewController!.presentViewController(alert, animated: true, completion: nil);


    return true
}

***注意：我还尝试将以下代码添加到 appDelegate 而不是上面的代码，但是每当我返回应用程序时，警报都会继续出现.....

func applicationDidBecomeActive(application: UIApplication) { //Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.

    showAlert();

}

func showAlert(){    
    println("alert");
    var alert = UIAlertController(
        title: "Welcome to WeddingApp!",
        message: "Thank You for choosing the \nWedding App for your organization needs. \n\nFor more great tools please visit our website www.wedme.com",
        preferredStyle: UIAlertControllerStyle.Alert);

    alert.addAction(UIAlertAction(title: "Continue", style: UIAlertActionStyle.Default, handler: nil));

    self.window!.rootViewController!.presentViewController(alert, animated: true, completion: nil);

}

有谁知道解决这个问题的方法？？？

Answer 1

在第一种情况下，您从未添加过 UIAlertController（您可以尝试将其添加为子视图控制器）。

https://stackoverflow.com/a/17012439/3324388

在第二种情况下，您将根控制器分配给 UIAlertController，而从未将根控制器分配回 UITabBarController。您需要重新设置它。

您是否尝试过使用 UIAlertView 代替？

https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIAlertView_Class/index.html

Answer 2

试试这样的：

func application(application: UIApplication!, didFinishLaunchingWithOptions launchOptions: NSDictionary!) -> Bool {

    if self.window!.rootViewController as? UITabBarController != nil {
        var tababarController = self.window!.rootViewController as UITabBarController
        .
        .
        .

        let alertController = UIAlertController(title: "Welcome...", message: "Thank You...", preferredStyle: .Alert)
        tababarController.presentViewController(alert, animated: true, completion: nil);
    }

    return true
}