无法在 AppDelegate 的 rootViewController 上显示 alertViewController

Question

我想在应用程序启动时在 AppDelegate 的 rootViewController 上显示 alertViewController。这里的代码片段：

 func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        let alert: UIAlertController = UIAlertController(title: "This is title", message: "This is message.", preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction(UIAlertAction(title: "Ok", style: .default))
        self.window?.rootViewController?.present(alert, animated: true, completion: nil)
        return true
 }

警报未出现在 rootViewController 上。请帮助我。

Answer 1

原因是视图尚未加载，如果您查看控制台，您可能会发现这样的日志：

Warning: Attempt to present on 'swiftHere.ViewController: 0x7ff289007740' whose view is not in the window hierarchy!

您可以调度它直到 rootViewController 加载：

DispatchQueue.main.asyncAfter(deadline: .now() + 2) {

       let alert: UIAlertController = UIAlertController(title: "This is title", message: "This is message.", preferredStyle: UIAlertControllerStyle.alert)
       alert.addAction(UIAlertAction(title: "Ok", style: .default))
      self.window?.rootViewController?.present(alert, animated: true, completion: nil)

    }

无法在 AppDelegate 的 rootViewController 上显示 alertViewController

Can't present alertViewController on rootViewController in AppDelegate

ios

appdelegate

swift

uialertviewcontroller