Lossing map state in combination with Jetpack Navigation UI / Fragment

[cleemansen]

Environment

• Android OS version: API 32
• Devices affected: Android Emulator
• Maps SDK Version: 10.5.0

Observed behavior and steps to reproduce

Loosing state as I am navigating back to start destination. See demo:

1. Starting on first tab of bottom navigation bar: Home
2. Moving camera away from New York
3. Navigating to second Tab (and scrolling down the list-view)
4. Navigating back to first tab
5. Camera moved to initial camera position New York. My view-state was not retained.

https://user-images.githubusercontent.com/868171/172797888-40ff0756-6f0e-4366-8e57-6d0c091bb6bb.mov

Expected behavior

The map state retains

Notes / preliminary analysis

• as you can see in the final step (navigating again to second tab) the list-view retains its state
• this MRE is based on NavigationAdvandedSample
• you can apply this patch to reproduce the MRE patch_navigation-ui_mapbox.txt

Additional links and references

I disucussed this situation in past also with the android team.

[cleemansen]

As a first workaround I cache the camera-position on my own and retain it during map recreation

import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import com.mapbox.maps.*

class MapFragment : Fragment() {

    private var mapView: MapView? = null
    private var retainedCamera: CameraState? = null

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val view = inflater.inflate(R.layout.fragment_map, container, false)
        mapView = view.findViewById(R.id.mapView)
        mapView?.getMapboxMap()?.loadStyleUri(Style.SATELLITE_STREETS)
        // workaround for https://github.com/mapbox/mapbox-maps-android/issues/1418
        if (retainedCamera != null) {
            mapView
                ?.getMapboxMap()
                ?.setCamera(CameraOptions.Builder()
                    .zoom(retainedCamera!!.zoom)
                    .center(retainedCamera!!.center)
                    .pitch(retainedCamera!!.pitch)
                    .bearing(retainedCamera!!.bearing)
                    .padding(retainedCamera!!.padding)
                    .build()
                )
        }
        return view
    }

    override fun onPause() {
        super.onPause()
        retainedCamera = mapView?.getMapboxMap()?.cameraState
    }

}