Improve lifecycle management, compass reliability, and accessibility

- Use repeatOnLifecycle(STARTED) for location updates so GPS stops
  when Activity is paused (battery conservation)
- Pair enableMyLocation/disableMyLocation with onResume/onPause
- Add low-pass filter for accelerometer+magnetometer compass fallback
  to reduce arrow jitter
- Detect missing compass sensors and show warning instead of frozen
  arrow
- Monitor compass accuracy via onAccuracyChanged and indicate
  degraded readings
- Show permission rationale dialog using existing i18n strings
- Guide user to Settings when location permission is permanently
  denied
- Check cacheMapArea return value and show banner on failure
- Add error handling around shelter Flow and location Flow collection
- Add contentDescription to direction arrow views for screen readers
- Use safe casts for system services (as? instead of as)
- Use explicit dark theme parent (Theme.Material3.Dark.NoActionBar)
  instead of DayNight with hardcoded dark colors
- Add error_no_compass and direction_arrow_description strings in
  en/nb/nn

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src/main/java/no/naiv/tilfluktsrom/MainActivity.kt

@@ -2,6 +2,7 @@ package no.naiv.tilfluktsrom
 
 import android.Manifest
 import android.content.Context
+import android.content.Intent
 import android.content.pm.PackageManager
 import android.hardware.Sensor
 import android.hardware.SensorEvent
@@ -10,17 +11,22 @@ import android.hardware.SensorManager
 import android.location.Location
 import android.net.ConnectivityManager
 import android.net.NetworkCapabilities
+import android.net.Uri
 import android.os.Bundle
+import android.provider.Settings
 import android.util.Log
 import android.view.View
 import android.widget.Toast
 import androidx.activity.result.contract.ActivityResultContracts
+import androidx.appcompat.app.AlertDialog
 import androidx.appcompat.app.AppCompatActivity
+import androidx.core.app.ActivityCompat
 import androidx.core.content.ContextCompat
+import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.lifecycleScope
-import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.lifecycle.repeatOnLifecycle
+import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.Job
-import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.launch
 import no.naiv.tilfluktsrom.data.MapCacheManager
@@ -50,7 +56,7 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
     private lateinit var repository: ShelterRepository
     private lateinit var locationProvider: LocationProvider
     private lateinit var mapCacheManager: MapCacheManager
-    private lateinit var sensorManager: SensorManager
+    private var sensorManager: SensorManager? = null
     private lateinit var shelterAdapter: ShelterListAdapter
 
     private var myLocationOverlay: MyLocationNewOverlay? = null
@@ -59,12 +65,14 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
     private var nearestShelters: List<ShelterWithDistance> = emptyList()
     private var deviceHeading = 0f
     private var isCompassMode = false
-    private var locationJob: Job? = null
     private var cachingJob: Job? = null
     // Map from shelter lokalId to its map marker, for icon swapping on selection
     private var shelterMarkerMap: MutableMap<String, Marker> = mutableMapOf()
     private var highlightedMarkerId: String? = null
 
+    // Whether a compass sensor is available on this device
+    private var hasCompassSensor = false
+
     // The currently selected shelter — can be any shelter, not just one from nearestShelters
     private var selectedShelter: ShelterWithDistance? = null
     // When true, location updates won't auto-select the nearest shelter
@@ -80,10 +88,29 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
 
         if (fineGranted || coarseGranted) {
             startLocationUpdates()
+        } else {
+            // Check if user permanently denied (don't show rationale = permanently denied)
+            val shouldShowRationale = ActivityCompat.shouldShowRequestPermissionRationale(
+                this, Manifest.permission.ACCESS_FINE_LOCATION
+            )
+            if (!shouldShowRationale) {
+                // Permission permanently denied — guide user to settings
+                AlertDialog.Builder(this)
+                    .setTitle(R.string.permission_location_title)
+                    .setMessage(R.string.permission_denied)
+                    .setPositiveButton(android.R.string.ok) { _, _ ->
+                        val intent = Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS).apply {
+                            data = Uri.fromParts("package", packageName, null)
+                        }
+                        startActivity(intent)
+                    }
+                    .setNegativeButton(android.R.string.cancel, null)
+                    .show()
             } else {
                 Toast.makeText(this, R.string.permission_denied, Toast.LENGTH_LONG).show()
             }
         }
+    }
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -93,7 +120,7 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
         repository = ShelterRepository(this)
         locationProvider = LocationProvider(this)
         mapCacheManager = MapCacheManager(this)
-        sensorManager = getSystemService(Context.SENSOR_SERVICE) as SensorManager
+        sensorManager = getSystemService(Context.SENSOR_SERVICE) as? SensorManager
 
         setupMap()
         setupShelterList()
@@ -122,9 +149,7 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
             // Add user location overlay
             myLocationOverlay = MyLocationNewOverlay(
                 GpsMyLocationProvider(this@MainActivity), this
-            ).apply {
+            )
-                enableMyLocation()
-            }
             overlays.add(myLocationOverlay)
         }
     }
@@ -137,7 +162,7 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
         }
 
         binding.shelterList.apply {
-            layoutManager = LinearLayoutManager(this@MainActivity)
+            layoutManager = androidx.recyclerview.widget.LinearLayoutManager(this@MainActivity)
             adapter = shelterAdapter
         }
     }
@@ -199,12 +224,19 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
 
             // Observe shelter data reactively
             launch {
+                try {
                     repository.getAllShelters().collectLatest { shelters ->
                         allShelters = shelters
                         binding.statusText.text = getString(R.string.status_shelters_loaded, shelters.size)
                         updateShelterMarkers()
                         currentLocation?.let { updateNearestShelters(it) }
                     }
+                } catch (e: CancellationException) {
+                    throw e
+                } catch (e: Exception) {
+                    Log.e(TAG, "Error observing shelter data", e)
+                    binding.statusText.text = getString(R.string.error_download_failed)
+                }
             }
 
             // Request location and start updates
@@ -216,6 +248,8 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
                     val success = repository.refreshData()
                     if (success) {
                         Toast.makeText(this@MainActivity, R.string.update_success, Toast.LENGTH_SHORT).show()
+                    } else {
+                        Toast.makeText(this@MainActivity, R.string.update_failed, Toast.LENGTH_SHORT).show()
                     }
                 }
             }
@@ -225,7 +259,30 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
     private fun requestLocationPermission() {
         if (locationProvider.hasLocationPermission()) {
             startLocationUpdates()
+            return
+        }
+
+        // Show rationale dialog if needed, then request
+        if (ActivityCompat.shouldShowRequestPermissionRationale(
+                this, Manifest.permission.ACCESS_FINE_LOCATION
+            )
+        ) {
+            AlertDialog.Builder(this)
+                .setTitle(R.string.permission_location_title)
+                .setMessage(R.string.permission_location_message)
+                .setPositiveButton(android.R.string.ok) { _, _ ->
+                    launchPermissionRequest()
+                }
+                .setNegativeButton(android.R.string.cancel) { _, _ ->
+                    Toast.makeText(this, R.string.permission_denied, Toast.LENGTH_LONG).show()
+                }
+                .show()
         } else {
+            launchPermissionRequest()
+        }
+    }
+
+    private fun launchPermissionRequest() {
         locationPermissionRequest.launch(
             arrayOf(
                 Manifest.permission.ACCESS_FINE_LOCATION,
@@ -233,11 +290,12 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
             )
         )
     }
-    }
 
     private fun startLocationUpdates() {
-        locationJob?.cancel()
+        // Use repeatOnLifecycle(STARTED) so GPS stops when Activity is paused
-        locationJob = lifecycleScope.launch {
+        lifecycleScope.launch {
+            repeatOnLifecycle(Lifecycle.State.STARTED) {
+                try {
                     locationProvider.locationUpdates().collectLatest { location ->
                         currentLocation = location
                         updateNearestShelters(location)
@@ -256,6 +314,13 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
                             }
                         }
                     }
+                } catch (e: CancellationException) {
+                    throw e
+                } catch (e: Exception) {
+                    Log.e(TAG, "Location updates failed", e)
+                    binding.statusText.text = getString(R.string.status_no_location)
+                }
+            }
         }
     }
 
@@ -357,14 +422,21 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
             R.string.shelter_capacity, selected.shelter.plasser
         ) + " - " + distanceText
 
-        // Update mini arrow in bottom sheet
+        // Update direction arrows with accessibility descriptions
         val bearing = selected.bearingDegrees.toFloat()
-        binding.miniArrow.setDirection(bearing - deviceHeading)
+        val arrowAngle = bearing - deviceHeading
+        binding.miniArrow.setDirection(arrowAngle)
+        binding.miniArrow.contentDescription = getString(
+            R.string.direction_arrow_description, distanceText
+        )
 
         // Update compass view
         binding.compassDistanceText.text = distanceText
         binding.compassAddressText.text = selected.shelter.adresse
-        binding.directionArrow.setDirection(bearing - deviceHeading)
+        binding.directionArrow.setDirection(arrowAngle)
+        binding.directionArrow.contentDescription = getString(
+            R.string.direction_arrow_description, distanceText
+        )
 
         // Emphasize the selected marker on the map
         highlightSelectedMarker(selected.shelter.lokalId)
@@ -465,14 +537,18 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
         binding.loadingButtonRow.visibility = View.GONE
 
         cachingJob = lifecycleScope.launch {
-            mapCacheManager.cacheMapArea(
+            val success = mapCacheManager.cacheMapArea(
                 binding.mapView, latitude, longitude
             ) { progress ->
                 binding.loadingText.text = getString(R.string.loading_map) +
                     " (${(progress * 100).toInt()}%)"
             }
             hideLoading()
+            if (success) {
                 binding.statusText.text = getString(R.string.status_shelters_loaded, allShelters.size)
+            } else {
+                showNoCacheBanner()
+            }
         }
     }
 
@@ -509,7 +585,8 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
     }
 
     private fun isNetworkAvailable(): Boolean {
-        val cm = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+        val cm = getSystemService(Context.CONNECTIVITY_SERVICE) as? ConnectivityManager
+            ?: return false
         val network = cm.activeNetwork ?: return false
         val caps = cm.getNetworkCapabilities(network) ?: return false
         return caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
@@ -520,18 +597,28 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
     override fun onResume() {
         super.onResume()
         binding.mapView.onResume()
+        myLocationOverlay?.enableMyLocation()
 
-        // Register for rotation vector (best compass source)
+        val sm = sensorManager ?: return
-        val rotationSensor = sensorManager.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR)
+
+        // Try rotation vector first (best compass source)
+        val rotationSensor = sm.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR)
         if (rotationSensor != null) {
-            sensorManager.registerListener(this, rotationSensor, SensorManager.SENSOR_DELAY_UI)
+            sm.registerListener(this, rotationSensor, SensorManager.SENSOR_DELAY_UI)
+            hasCompassSensor = true
         } else {
             // Fallback to accelerometer + magnetometer
-            sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER)?.let {
+            val accel = sm.getDefaultSensor(Sensor.TYPE_ACCELEROMETER)
-                sensorManager.registerListener(this, it, SensorManager.SENSOR_DELAY_UI)
+            val mag = sm.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD)
-            }
+            if (accel != null && mag != null) {
-            sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD)?.let {
+                sm.registerListener(this, accel, SensorManager.SENSOR_DELAY_UI)
-                sensorManager.registerListener(this, it, SensorManager.SENSOR_DELAY_UI)
+                sm.registerListener(this, mag, SensorManager.SENSOR_DELAY_UI)
+                hasCompassSensor = true
+                Log.w(TAG, "Using accelerometer+magnetometer fallback for compass")
+            } else {
+                hasCompassSensor = false
+                Log.e(TAG, "No compass sensors available on this device")
+                binding.compassAddressText.text = getString(R.string.error_no_compass)
             }
         }
     }
@@ -539,7 +626,8 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
     override fun onPause() {
         super.onPause()
         binding.mapView.onPause()
-        sensorManager.unregisterListener(this)
+        myLocationOverlay?.disableMyLocation()
+        sensorManager?.unregisterListener(this)
     }
 
     private val gravity = FloatArray(3)
@@ -557,16 +645,23 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
                 updateDirectionArrows()
             }
             Sensor.TYPE_ACCELEROMETER -> {
-                System.arraycopy(event.values, 0, gravity, 0, 3)
+                lowPassFilter(event.values, gravity)
                 updateFromAccelMag()
             }
             Sensor.TYPE_MAGNETIC_FIELD -> {
-                System.arraycopy(event.values, 0, geomagnetic, 0, 3)
+                lowPassFilter(event.values, geomagnetic)
                 updateFromAccelMag()
             }
         }
     }
 
+    /** Low-pass filter to smooth noisy accelerometer/magnetometer data. */
+    private fun lowPassFilter(input: FloatArray, output: FloatArray, alpha: Float = 0.25f) {
+        for (i in input.indices) {
+            output[i] = output[i] + alpha * (input[i] - output[i])
+        }
+    }
+
     private fun updateFromAccelMag() {
         val r = FloatArray(9)
         if (SensorManager.getRotationMatrix(r, null, gravity, geomagnetic)) {
@@ -587,6 +682,28 @@ class MainActivity : AppCompatActivity(), SensorEventListener {
     }
 
     override fun onAccuracyChanged(sensor: Sensor?, accuracy: Int) {
-        // No-op
+        if (sensor?.type == Sensor.TYPE_MAGNETIC_FIELD ||
+            sensor?.type == Sensor.TYPE_ROTATION_VECTOR
+        ) {
+            when (accuracy) {
+                SensorManager.SENSOR_STATUS_UNRELIABLE,
+                SensorManager.SENSOR_STATUS_ACCURACY_LOW -> {
+                    Log.w(TAG, "Compass accuracy degraded: $accuracy")
+                    binding.compassAddressText.let { tv ->
+                        val current = selectedShelter?.shelter?.adresse ?: ""
+                        if (!current.contains("⚠")) {
+                            tv.text = "⚠ $current"
+                        }
+                    }
+                }
+                SensorManager.SENSOR_STATUS_ACCURACY_MEDIUM,
+                SensorManager.SENSOR_STATUS_ACCURACY_HIGH -> {
+                    // Restore normal display when accuracy improves
+                    selectedShelter?.let { selected ->
+                        binding.compassAddressText.text = selected.shelter.adresse
+                    }
+                }
+            }
+        }
     }
 }

app/src/main/res/values-nb/strings.xml

@@ -40,6 +40,10 @@
     <!-- Feil -->
     <string name="error_download_failed">Kunne ikke laste ned tilfluktsromdata. Sjekk internettforbindelsen.</string>
     <string name="error_no_data_offline">Ingen lagrede data tilgjengelig. Koble til internett for å laste ned tilfluktsromdata.</string>
+    <string name="error_no_compass">Kompass er ikke tilgjengelig på denne enheten</string>
     <string name="update_success">Tilfluktsromdata oppdatert</string>
     <string name="update_failed">Oppdatering mislyktes — bruker lagrede data</string>
+
+    <!-- Tilgjengelighet -->
+    <string name="direction_arrow_description">Retning til tilfluktsrom, %s unna</string>
 </resources>

app/src/main/res/values-nn/strings.xml

@@ -40,6 +40,10 @@
     <!-- Feil -->
     <string name="error_download_failed">Kunne ikkje laste ned tilfluktsromdata. Sjekk internettilkoplinga.</string>
     <string name="error_no_data_offline">Ingen lagra data tilgjengeleg. Kopla til internett for å laste ned tilfluktsromdata.</string>
+    <string name="error_no_compass">Kompass er ikkje tilgjengeleg på denne eininga</string>
     <string name="update_success">Tilfluktsromdata oppdatert</string>
     <string name="update_failed">Oppdatering mislukkast — brukar lagra data</string>
+
+    <!-- Tilgjenge -->
+    <string name="direction_arrow_description">Retning til tilfluktsrom, %s unna</string>
 </resources>

app/src/main/res/values/strings.xml

@@ -40,6 +40,10 @@
     <!-- Errors -->
     <string name="error_download_failed">Could not download shelter data. Check your internet connection.</string>
     <string name="error_no_data_offline">No cached data available. Connect to the internet to download shelter data.</string>
+    <string name="error_no_compass">Compass not available on this device</string>
     <string name="update_success">Shelter data updated</string>
     <string name="update_failed">Update failed — using cached data</string>
+
+    <!-- Accessibility -->
+    <string name="direction_arrow_description">Direction to shelter, %s away</string>
 </resources>

app/src/main/res/values/themes.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-    <style name="Theme.Tilfluktsrom" parent="Theme.Material3.DayNight.NoActionBar">
+    <style name="Theme.Tilfluktsrom" parent="Theme.Material3.Dark.NoActionBar">
         <item name="colorPrimary">@color/shelter_primary</item>
         <item name="colorPrimaryDark">@color/shelter_primary_dark</item>
         <item name="colorAccent">@color/shelter_accent</item>