Before this change, it was never possible to interact with the navigationController property in a pushed view controller's viewDidLoad property when using MDCAppBarNavigationController. This behavior is surprising for folks using UINavigationController, which does allow you to access navigationController from within viewDidLoad.
This expectation is an anti-pattern (e.g. viewDidLoad is never guaranteed to be invoked after a view controller has been pushed onto a navigationController stack), but the goal of MDCAppBarNavigationController is to provide a drop-in replacement for UINavigationController so our intent is to align behaviors, even if they're not necessarily for the right reasons.
All that being said, the change introduced in this CL simply swaps the ordering of pushing the view controller and injecting the AppBar, such that the injection now happens after the super implementation of pushViewController has been invoked. This allows the viewDidLoad logic to be invoked after navigationController has been initialized on the view controller.
The reason we were doing it the other way before was so that the AppBar could intercept the relevant status bar appearance events. We work around that requirement in this change by invoking setNeedsStatusBarAppearanceUpdate and setNeedsUpdateOfHomeIndicatorAutoHidden immediately after injecting the AppBar.
PiperOrigin-RevId: 313410464
Before this change, it was never possible to interact with the navigationController property in a pushed view controller's viewDidLoad property when using MDCAppBarNavigationController. This behavior is surprising for folks using UINavigationController, which does allow you to access navigationController from within viewDidLoad.
This expectation is an anti-pattern (e.g. viewDidLoad is never guaranteed to be invoked after a view controller has been pushed onto a navigationController stack), but the goal of MDCAppBarNavigationController is to provide a drop-in replacement for UINavigationController so our intent is to align behaviors, even if they're not necessarily for the right reasons.
All that being said, the change introduced in this CL simply swaps the ordering of pushing the view controller and injecting the AppBar, such that the injection now happens after the super implementation of pushViewController has been invoked. This allows the viewDidLoad logic to be invoked after navigationController has been initialized on the view controller.
The reason we were doing it the other way before was so that the AppBar could intercept the relevant status bar appearance events. We work around that requirement in this change by invoking setNeedsStatusBarAppearanceUpdate and setNeedsUpdateOfHomeIndicatorAutoHidden immediately after injecting the AppBar.
PiperOrigin-RevId: 311342757
