IssueTracker

Component used: Activity

Versions used:
androidx.activity: 1.9.3
androidx.navigation: 2.8.4

Devices/Android versions reproduced on:
Pixel emulators API 34 and 35
Samsung S22 API 34

When adding a OnBackPressedCallback in an Activity via OnBackPressedDispatcher.addCallback, the callback is incorrectly triggered in favor of lower level default navigation behavior or manual compose BackHandler calls after backgrounding the app and returning.

This issue seems to occur in all of the following cases

1. Compose code within a Fragment uses a NavHost without any custom BackHandler
2. Compose code within a Fragment uses a NavHost with a custom BackHandler
3. Compose code within a Fragment that does not use a NavHost but uses some other type of "navigation" like a boolean that determines if a further screen or dialog should be shown

In each case I would expect that default NavController behavior or manual BackHandler code would be executed instead of the MainActivity's OnBackPressedCallback. This is what happens without backgrounding the app, but once you background the app and return the MainActivity code is executed on back press.

Example code that reproduces the issue in a couple ways and offers a workaround. See further comments in the code for specific examples
https://github.com/JacobSense/backpress-bug

In the example app you can follow these steps to see the issue

1. Navigate to FragmentB (Screen B)
2. Navigate to ScreenC
3. Background the app
4. Return and tap hardware back. You would expect to be sent back to FragmentB (ScreenB) but you are taken back to MainFragment

If you require manual back handling, a workaround for BackHandler exists that seems to fix it.

The BackHandler code has this:

DisposableEffect(lifecycleOwner, backDispatcher) {
    backDispatcher.addCallback(lifecycleOwner, backCallback)
    onDispose {
        backCallback.remove()
    }
}

If you copy the function but replace DisposableEffect with LifecycleResumeEffect it works

LifecycleResumeEffect(lifecycleOwner, backDispatcher) {
    backDispatcher.addCallback(lifecycleOwner, backCallback)
    onPauseOrDispose {
        backCallback.remove()
    }
}

This is a pretty simple workaround if you need manual back handling. If your goal is the default behavior of navigating back to the start screen of the NavHost and then navigating back, you can add a workaround version of BackHandler to manually implement the default behavior.