throw out coroutine-based location request flow :-(

The reason why this does not (always) work is because coroutines may not survive the app being tabbed out and tabbed in again (e.g. going to location settings). So the flow cannot be handled by coroutines on the lifecycle scope of the activity/fragment (see #3967)

app/src/main/java/de/westnordost/streetcomplete/screens/MainActivity.kt

@@ -1,6 +1,9 @@
 package de.westnordost.streetcomplete.screens
 
+import android.content.BroadcastReceiver
+import android.content.Context
 import android.content.Intent
+import android.content.IntentFilter
 import android.content.SharedPreferences
 import android.content.res.Configuration
 import android.net.ConnectivityManager
@@ -20,6 +23,7 @@ import androidx.core.content.getSystemService
 import androidx.core.text.parseAsHtml
 import androidx.fragment.app.commit
 import androidx.lifecycle.lifecycleScope
+import androidx.localbroadcastmanager.content.LocalBroadcastManager
 import androidx.preference.PreferenceManager
 import de.westnordost.streetcomplete.Prefs
 import de.westnordost.streetcomplete.R
@@ -52,7 +56,7 @@ import de.westnordost.streetcomplete.util.ktx.hasLocationPermission
 import de.westnordost.streetcomplete.util.ktx.isLocationEnabled
 import de.westnordost.streetcomplete.util.ktx.toast
 import de.westnordost.streetcomplete.util.location.LocationAvailabilityReceiver
-import de.westnordost.streetcomplete.util.location.LocationRequester
+import de.westnordost.streetcomplete.util.location.LocationRequestFragment
 import de.westnordost.streetcomplete.util.parseGeoUri
 import de.westnordost.streetcomplete.view.dialogs.RequestLoginDialog
 import kotlinx.coroutines.launch
@@ -78,10 +82,16 @@ class MainActivity :
     private val questPresetsSource: QuestPresetsSource by inject()
     private val prefs: SharedPreferences by inject()
 
-    private val requestLocation = LocationRequester(this, this)
-
     private var mainFragment: MainFragment? = null
 
+    private val requestLocationPermissionResultReceiver: BroadcastReceiver = object : BroadcastReceiver() {
+        override fun onReceive(context: Context, intent: Intent) {
+            if (!intent.getBooleanExtra(LocationRequestFragment.GRANTED, false)) {
+                toast(R.string.no_gps_no_quests, Toast.LENGTH_LONG)
+            }
+        }
+    }
+
     private val elementEditsListener = object : ElementEditsSource.Listener {
         override fun onAddedEdit(edit: ElementEdit) { lifecycleScope.launch { ensureLoggedIn() } }
         override fun onSyncedEdit(edit: ElementEdit) {}
@@ -97,6 +107,11 @@ class MainActivity :
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
+        LocalBroadcastManager.getInstance(this).registerReceiver(
+            requestLocationPermissionResultReceiver,
+            IntentFilter(LocationRequestFragment.REQUEST_LOCATION_PERMISSION_RESULT)
+        )
+
         lifecycle.addObserver(questAutoSyncer)
         crashReportExceptionHandler.askUserToSendCrashReportIfExists(this)
         PreferenceManager.setDefaultValues(this, R.xml.preferences, false)
@@ -108,6 +123,7 @@ class MainActivity :
 
         mainFragment = supportFragmentManager.findFragmentById(R.id.map_fragment) as MainFragment?
         if (savedInstanceState == null) {
+            supportFragmentManager.commit { add(LocationRequestFragment(), TAG_LOCATION_REQUEST) }
             val hasShownTutorial = prefs.getBoolean(Prefs.HAS_SHOWN_TUTORIAL, false)
             if (!hasShownTutorial && !userLoginStatusController.isLoggedIn) {
                 supportFragmentManager.commit {
@@ -332,15 +348,7 @@ class MainActivity :
     /* ------------------------------- TutorialFragment.Listener -------------------------------- */
 
     override fun onTutorialFinished() {
-        lifecycleScope.launch {
-            val hasLocation = requestLocation()
-            // if denied first time after exiting tutorial: ask again once (i.e. show rationale and ask again)
-            if (!hasLocation) {
-                requestLocation()
-            } else {
-                toast(R.string.no_gps_no_quests, Toast.LENGTH_LONG)
-            }
-        }
+        requestLocation()
 
         prefs.edit { putBoolean(Prefs.HAS_SHOWN_TUTORIAL, true) }
 
@@ -353,6 +361,10 @@ class MainActivity :
         }
     }
 
+    private fun requestLocation() {
+        (supportFragmentManager.findFragmentByTag(TAG_LOCATION_REQUEST) as? LocationRequestFragment)?.startRequest()
+    }
+
     /* ------------------------------------ Location listener ----------------------------------- */
 
     private fun updateLocationAvailability(isAvailable: Boolean) {
@@ -364,6 +376,8 @@ class MainActivity :
     }
 
     companion object {
+        private const val TAG_LOCATION_REQUEST = "LocationRequestFragment"
+
         // per application start settings
         private var dontShowRequestAuthorizationAgain = false
     }

app/src/main/java/de/westnordost/streetcomplete/screens/main/MainFragment.kt

@@ -30,7 +30,6 @@ import androidx.core.view.isVisible
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.FragmentManager
 import androidx.fragment.app.commit
-import androidx.lifecycle.lifecycleScope
 import de.westnordost.streetcomplete.ApplicationConstants
 import de.westnordost.streetcomplete.Prefs
 import de.westnordost.streetcomplete.R
@@ -75,6 +74,7 @@ import de.westnordost.streetcomplete.quests.IsShowingQuestDetails
 import de.westnordost.streetcomplete.quests.LeaveNoteInsteadFragment
 import de.westnordost.streetcomplete.quests.note_discussion.NoteDiscussionForm
 import de.westnordost.streetcomplete.screens.HandlesOnBackPressed
+import de.westnordost.streetcomplete.screens.MainActivity
 import de.westnordost.streetcomplete.screens.main.bottom_sheet.CreateNoteFragment
 import de.westnordost.streetcomplete.screens.main.bottom_sheet.IsCloseableBottomSheet
 import de.westnordost.streetcomplete.screens.main.bottom_sheet.IsMapOrientationAware
@@ -106,7 +106,7 @@ import de.westnordost.streetcomplete.util.ktx.toast
 import de.westnordost.streetcomplete.util.ktx.viewLifecycleScope
 import de.westnordost.streetcomplete.util.location.FineLocationManager
 import de.westnordost.streetcomplete.util.location.LocationAvailabilityReceiver
-import de.westnordost.streetcomplete.util.location.LocationRequester
+import de.westnordost.streetcomplete.util.location.LocationRequestFragment
 import de.westnordost.streetcomplete.util.math.area
 import de.westnordost.streetcomplete.util.math.enclosingBoundingBox
 import de.westnordost.streetcomplete.util.math.enlargedBy
@@ -174,7 +174,6 @@ class MainFragment :
     private val soundFx: SoundFx by inject()
     private val prefs: SharedPreferences by inject()
 
-    private lateinit var requestLocation: LocationRequester
     private lateinit var locationManager: FineLocationManager
 
     private val binding by viewBinding(FragmentMainBinding::bind)
@@ -207,7 +206,6 @@ class MainFragment :
     override fun onAttach(context: Context) {
         super.onAttach(context)
 
-        requestLocation = LocationRequester(requireActivity(), this)
         locationManager = FineLocationManager(context, this::onLocationChanged)
 
         childFragmentManager.addFragmentOnAttachListener { _, fragment ->
@@ -216,6 +214,7 @@ class MainFragment :
                 is MainMenuButtonFragment -> mainMenuButtonFragment = fragment
             }
         }
+        childFragmentManager.commit { add(LocationRequestFragment(), TAG_LOCATION_REQUEST) }
     }
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
@@ -728,7 +727,7 @@ class MainFragment :
 
         when {
             !binding.gpsTrackingButton.state.isEnabled -> {
-                lifecycleScope.launch { requestLocation() }
+                requestLocation()
             }
             !mapFragment.isFollowingPosition -> {
                 setIsFollowingPosition(true)
@@ -739,6 +738,10 @@ class MainFragment :
         }
     }
 
+    private fun requestLocation() {
+        (childFragmentManager.findFragmentByTag(TAG_LOCATION_REQUEST) as? LocationRequestFragment)?.startRequest()
+    }
+
     private fun onClickCreateButton() {
         showOverlayFormForNewElement()
     }
@@ -1165,5 +1168,7 @@ class MainFragment :
     companion object {
         private const val BOTTOM_SHEET = "bottom_sheet"
         private const val EDIT_HISTORY = "edit_history"
+
+        private const val TAG_LOCATION_REQUEST = "LocationRequestFragment"
     }
 }

app/src/main/java/de/westnordost/streetcomplete/util/location/LocationAvailabilityReceiver.kt

@@ -36,7 +36,7 @@ class LocationAvailabilityReceiver(private val context: Context) {
         )
         LocalBroadcastManager.getInstance(context).registerReceiver(
             requestLocationPermissionResultReceiver,
-            IntentFilter(LocationRequester.REQUEST_LOCATION_PERMISSION_RESULT)
+            IntentFilter(LocationRequestFragment.REQUEST_LOCATION_PERMISSION_RESULT)
         )
     }