UIViewController selective Autorotation with Size classes

问题

The new size classes based Autorotation is a pain if you want custom behavior. Here are my requirements and flow:

• View Controller 1(VC1) modally presents View Controller 2 (VC2)

• VC1 only supports landscape, portrait, or both depending on user settings (achieved via supportedInterfaceOrientations). For this example, we assume it is locked to landscape,

• VC 2 supports both landscape & portrait

I use Size classes and in View Controller 1, I check for statusBarOrientation in viewWillTransition(to size...) to configure interface elements positioning & other customizations.

   override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {

    let orientation = UIApplication.shared.statusBarOrientation

    NSLog("View will transition to \(size), \(orientation.rawValue)")
    super.viewWillTransition(to: size, with: coordinator)


    coordinator.animate(alongsideTransition: { [unowned self] (_) in
    ....
    }
}

This works, except when VC 2 is presented and the device is rotated. VC 1 is all messed up when VC 2 is dismissed. To be sure, I would like to refresh layout of View Controller 1 when it appears. How do I do that? I tried UIViewController.attemptRotationToDeviceOrientation() but it doesn't force the autorotation methods to be called again.

EDIT: As can be seen, in VC1 I check for statusBarOrientation to determine interface orientation. That poses a problem, because statusBarOrientation gets changed to portrait when VC2 rotates to portrait mode. And viewWillTransition to size gets invoked on VC1 at the same time where I force layout to portrait mode.

来源：https://stackoverflow.com/questions/53364498/uiviewcontroller-selective-autorotation-with-size-classes