Orientation problem on iOS with GameCenter

Symptoms

• Calling the screen orientation changes from portrait to landscape mode, even if the project is set to use portrait mode only

Cause

If you are using the iOS presentation controller, this could override your orientation constraints. 

Resolution

As a workaround, you can modify the iOS trampoline code to use only the portrait mode.

Build for iOS and open UnityAppController.mm and replace supportedInterfaceOrientationsForWindow with the provided code:

- (NSUInteger)application:(UIApplication*)application supportedInterfaceOrientationsForWindow:(UIWindow*)window
{
    return (1 << UIInterfaceOrientationPortrait) | 
           (0 << UIInterfaceOrientationPortraitUpsideDown) | 
           (0 << UIInterfaceOrientationLandscapeRight) | 
           (0 << UIInterfaceOrientationLandscapeLeft);
}

This article applies to Unity versions 5.3.4p3 and higher