feat: foreground service for background message notifications

app/src/main/AndroidManifest.xml

@@ -4,6 +4,8 @@
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
     <uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_DATA_SYNC" />
 
     <application
         android:name=".BollwerkApp"
@@ -34,6 +36,11 @@
                 android:name="android.support.FILE_PROVIDER_PATHS"
                 android:resource="@xml/file_paths" />
         </provider>
+
+        <service
+            android:name=".service.MessagingService"
+            android:exported="false"
+            android:foregroundServiceType="dataSync" />
     </application>
 
 </manifest>

app/src/main/java/de/bollwerk/app/service/MessagingService.kt

@@ -0,0 +1,88 @@
+package de.bollwerk.app.service
+
+import android.app.Notification
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.app.Service
+import android.content.Context
+import android.content.Intent
+import android.content.pm.ServiceInfo
+import android.os.IBinder
+import androidx.core.app.NotificationCompat
+import de.bollwerk.app.MainActivity
+import de.bollwerk.app.R
+
+/**
+ * Foreground Service der den Prozess am Leben hält, damit die WebSocket-Verbindung
+ * auch im Hintergrund bestehen bleibt und Nachrichten empfangen werden können.
+ */
+class MessagingService : Service() {
+
+    override fun onCreate() {
+        super.onCreate()
+        createServiceChannel()
+    }
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
+        when (intent?.action) {
+            ACTION_STOP -> {
+                stopForeground(STOP_FOREGROUND_REMOVE)
+                stopSelf()
+                return START_NOT_STICKY
+            }
+        }
+        startForeground(NOTIFICATION_ID, buildNotification(), ServiceInfo.FOREGROUND_SERVICE_TYPE_DATA_SYNC)
+        return START_STICKY
+    }
+
+    override fun onBind(intent: Intent?): IBinder? = null
+
+    private fun createServiceChannel() {
+        val channel = NotificationChannel(
+            CHANNEL_ID,
+            "Verbindung",
+            NotificationManager.IMPORTANCE_LOW
+        ).apply {
+            description = "Hält die Verbindung zum Server für Nachrichten aufrecht"
+            setShowBadge(false)
+        }
+        val manager = getSystemService(NotificationManager::class.java)
+        manager.createNotificationChannel(channel)
+    }
+
+    private fun buildNotification(): Notification {
+        val openIntent = PendingIntent.getActivity(
+            this,
+            0,
+            Intent(this, MainActivity::class.java),
+            PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
+        )
+
+        return NotificationCompat.Builder(this, CHANNEL_ID)
+            .setSmallIcon(R.drawable.ic_notification_message)
+            .setContentTitle("Bollwerk")
+            .setContentText("Verbunden – Nachrichten werden empfangen")
+            .setOngoing(true)
+            .setContentIntent(openIntent)
+            .build()
+    }
+
+    companion object {
+        private const val CHANNEL_ID = "bollwerk_service"
+        private const val NOTIFICATION_ID = 9001
+        const val ACTION_STOP = "de.bollwerk.app.STOP_MESSAGING_SERVICE"
+
+        fun start(context: Context) {
+            val intent = Intent(context, MessagingService::class.java)
+            context.startForegroundService(intent)
+        }
+
+        fun stop(context: Context) {
+            val intent = Intent(context, MessagingService::class.java).apply {
+                action = ACTION_STOP
+            }
+            context.startService(intent)
+        }
+    }
+}

app/src/main/java/de/bollwerk/app/ui/MainViewModel.kt

@@ -1,9 +1,11 @@
 package de.bollwerk.app.ui
 
+import android.content.Context
 import android.util.Log
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
+import dagger.hilt.android.qualifiers.ApplicationContext
 import de.bollwerk.app.data.sync.WebSocketClient
 import de.bollwerk.app.data.sync.WebSocketEvent
 import de.bollwerk.app.domain.AuthEventBus
@@ -11,6 +13,7 @@ import de.bollwerk.app.domain.model.SettingsKey.StringKey
 import de.bollwerk.app.domain.repository.ImportExportRepository
 import de.bollwerk.app.domain.repository.SettingsRepository
 import de.bollwerk.app.domain.repository.SyncService
+import de.bollwerk.app.service.MessagingService
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.asSharedFlow
@@ -25,6 +28,7 @@ internal class MainViewModel @Inject constructor(
     private val webSocketClient: WebSocketClient,
     private val settingsRepository: SettingsRepository,
     private val importExportRepository: ImportExportRepository,
+    @ApplicationContext private val context: Context
 ) : ViewModel() {
 
     private val _navigateToSettings = MutableSharedFlow<Unit>(extraBufferCapacity = 1)
@@ -45,6 +49,7 @@ internal class MainViewModel @Inject constructor(
             if (token.isNotBlank() && serverUrl.isNotBlank()) {
                 Log.i(TAG, "App-Start: Token vorhanden – verbinde WebSocket")
                 webSocketClient.connect(serverUrl, token)
+                MessagingService.start(context)
             } else {
                 Log.d(TAG, "App-Start: Kein Token – kein WebSocket")
             }
@@ -57,6 +62,7 @@ internal class MainViewModel @Inject constructor(
             authEventBus.loginSuccess.collect { (serverUrl, token) ->
                 Log.i(TAG, "Login erfolgreich – verbinde WebSocket")
                 webSocketClient.connect(serverUrl, token)
+                MessagingService.start(context)
             }
         }
     }
@@ -68,6 +74,7 @@ internal class MainViewModel @Inject constructor(
                 Log.w(TAG, "Session abgelaufen – Forced-Logout")
                 syncService.logout()
                 webSocketClient.disconnect()
+                MessagingService.stop(context)
                 _navigateToSettings.emit(Unit)
             }
         }

app/src/main/java/de/bollwerk/app/ui/settings/SettingsViewModel.kt

@@ -21,6 +21,7 @@ import de.bollwerk.app.domain.model.toJson
 import de.bollwerk.app.domain.repository.ImportExportRepository
 import de.bollwerk.app.domain.repository.SettingsRepository
 import de.bollwerk.app.domain.repository.SyncService
+import de.bollwerk.app.service.MessagingService
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -230,6 +231,7 @@ internal class SettingsViewModel @Inject constructor(
         viewModelScope.launch {
             syncService.logout()
             webSocketClient.disconnect()
+            MessagingService.stop(context)
             _uiState.update {
                 it.copy(
                     isLoggedIn = false,