Androidx Navigation IllegalStateException after onSaveInstanceState

Question

I have an app using AndroidX's Navigation library, but I'm getting odd behavior. Particularly around my app going in/out of the background. Here are two examples:

In a simple on click listener in a Fragment I have:

(Kotlin)

button.setOnClickListener {
    findNavController().popBackStack()
}

From this, I see crashes saying it threw an IllegalStateException since it ran after onSaveInstanceState.

I have a ViewModel associated with my Fragment and I register my observers to the fragment view's lifecycle. This means that I get notified during onStart. Some key events, such as login state determine the app's navigation. In my case I have a splash screen that could go to either a login screen or the main screen. Once a user completes login, I reset the navigation (taking me back to the splash screen). Now the auth state is ready and I want to navigate to the main fragment, this throws an error often because onResume must be called before the FragmentManager is considered ready. I get an error saying I'm in the middle of a transaction and I can't add a new one. To mediate this I had to write this strange bit of code:

(Kotlin)

private fun safeNavigateToMain() {
    if (fragmentManager == null) {
      return
    }
    if (!isResumed) {
        view?.post { safeNavigateToMain() }
        return
    }
    try {
        findNavController().navigate(R.id.main)
    } catch (tr: Throwable) {
        view?.post { safeNavigateToMain() }
    }
}

Does anyone know how I can get the navigation controller to play nice with the fragment lifecycles without having to add these workarounds?

1.0.0-alpha02 for the fragment and ui, and 1.0.0-alpha01 for the plugin during the crashes, updated to 02 recently but that build hasn't hit production yet so I don't have any stack traces yet. — TheHebrewHammer, Jun 21 '18 at 13:51

score 0 · Accepted Answer · answered Jul 13 '18 at 16:27

0

As per the Navigation 1.0.0-alpha03 release notes:

FragmentNavigator now ignores navigation operations after FragmentManager has saved state, avoiding “Can not perform this action after onSaveInstanceState” exceptions b/110987825

So upgrading to alpha03 should remove this error.

answered Jul 13 '18 at 16:27

ianhanniballake

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Is it possible to use `commitAllowingStateLoss` with Navigation Component? – bitvale Oct 01 '19 at 18:55
1

@bitvale - no. You shouldn't be losing state at all. – ianhanniballake Oct 01 '19 at 18:59

Androidx Navigation IllegalStateException after onSaveInstanceState

1 Answers1