Xcode - Show a ViewController when the app becomes active (coming back from the background)

问题

I want to show a specific ViewController when the app comes foregrounded from the background.

I am using this method to call a ViewController.

- (void)applicationWillEnterForeground:(UIApplication *)application
{
  [self presentMyViewController];
}

But there is a delay when it comes back from the background. Or in other words, you can see the previous view, then you see the ViewController. I don't want to show the previous view at all.

How can achieve this?

回答1:

Hide the old view before the app is backgrounded, in your app delegate's applicationDidEnterBackground: method. This is in fact a mechanism that Apple specifically recommends for privacy reasons here:

Remove sensitive information from views before moving to the background. When an app transitions to the background, the system takes a snapshot of the app’s main window, which it then presents briefly when transitioning your app back to the foreground. Before returning from your applicationDidEnterBackground: method, you should hide or obscure passwords and other sensitive personal information that might be captured as part of the snapshot.

回答2:

If the app comes to the foreground, it must previously have gone into the background. So call presentMyViewController then, when the app has gone into the background.

来源：https://stackoverflow.com/questions/16290685/xcode-show-a-viewcontroller-when-the-app-becomes-active-coming-back-from-the