You can't control that the app appears, that's managed by the OS.
You can detect when the app is going to be backgrounded and hide the information you don't want to be visible.
From Apple:
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.
Use applicationDidEnterBackground
to detect when the app is going to be backgrounded