[android] Implement foreground notification service (#480)

A notification is shown when emulation is active. This, in theory should help preventing Eden for getting destroyed in the background. It is also a nice Q.O.L feature to have.

Credits go to t895 for the initial implementation. This was back-ported from older official Citra builds, although with crashes which i fixed myself.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/480
Reviewed-by: crueter <crueter@eden-emu.dev>
Co-authored-by: nyx <contact@innix.space>
Co-committed-by: nyx <contact@innix.space>

src/android/app/src/main/AndroidManifest.xml

@@ -27,6 +27,8 @@ SPDX-License-Identifier: GPL-3.0-or-later
     <uses-permission android:name="android.permission.WRITE_SECURE_SETTINGS" android:required="false" />
     <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
     <uses-permission android:name="android.permission.BLUETOOTH_SCAN" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_SPECIAL_USE" />
     <uses-permission android:name="android.permission.BLUETOOTH" android:maxSdkVersion="30" />
     <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" android:maxSdkVersion="30" />
 
@@ -93,6 +95,10 @@ SPDX-License-Identifier: GPL-3.0-or-later
             <meta-data android:name="android.nfc.action.TECH_DISCOVERED" android:resource="@xml/nfc_tech_filter" />
         </activity>
 
+        <service android:name="org.yuzu.yuzu_emu.utils.ForegroundService" android:foregroundServiceType="specialUse">
+            <property android:name="android.app.PROPERTY_SPECIAL_USE_FGS_SUBTYPE" android:value="Keep emulation running in background"/>
+        </service>
+
         <provider
             android:name=".features.DocumentProvider"
             android:authorities="${applicationId}.user"

src/android/app/src/main/java/org/yuzu/yuzu_emu/YuzuApplication.kt

@@ -22,6 +22,17 @@ fun Context.getPublicFilesDir(): File = getExternalFilesDir(null) ?: filesDir
 
 class YuzuApplication : Application() {
     private fun createNotificationChannels() {
+        val name: CharSequence = getString(R.string.app_notification_channel_name)
+        val description = getString(R.string.app_notification_channel_description)
+        val foregroundService = NotificationChannel(
+            getString(R.string.app_notification_channel_id),
+            name,
+            NotificationManager.IMPORTANCE_DEFAULT
+        )
+        foregroundService.description = description
+        foregroundService.setSound(null, null)
+        foregroundService.vibrationPattern = null
+
         val noticeChannel = NotificationChannel(
             getString(R.string.notice_notification_channel_id),
             getString(R.string.notice_notification_channel_name),
@@ -34,6 +45,7 @@ class YuzuApplication : Application() {
         // or other notification behaviors after this
         val notificationManager = getSystemService(NotificationManager::class.java)
         notificationManager.createNotificationChannel(noticeChannel)
+        notificationManager.createNotificationChannel(foregroundService)
     }
 
     override fun onCreate() {

src/android/app/src/main/java/org/yuzu/yuzu_emu/activities/EmulationActivity.kt

@@ -7,6 +7,7 @@
 package org.yuzu.yuzu_emu.activities
 
 import android.annotation.SuppressLint
+import android.app.Activity
 import android.app.PendingIntent
 import android.app.PictureInPictureParams
 import android.app.RemoteAction
@@ -59,6 +60,7 @@ import org.yuzu.yuzu_emu.utils.ParamPackage
 import org.yuzu.yuzu_emu.utils.ThemeHelper
 import java.text.NumberFormat
 import kotlin.math.roundToInt
+import org.yuzu.yuzu_emu.utils.ForegroundService
 
 class EmulationActivity : AppCompatActivity(), SensorEventListener {
     private lateinit var binding: ActivityEmulationBinding
@@ -78,6 +80,8 @@ class EmulationActivity : AppCompatActivity(), SensorEventListener {
 
     private val emulationViewModel: EmulationViewModel by viewModels()
 
+    private var foregroundService: Intent? = null
+
     override fun onCreate(savedInstanceState: Bundle?) {
         Log.gameLaunched = true
         ThemeHelper.setTheme(this)
@@ -128,6 +132,9 @@ class EmulationActivity : AppCompatActivity(), SensorEventListener {
         nfcReader = NfcReader(this)
         nfcReader.initialize()
 
+        foregroundService = Intent(this, ForegroundService::class.java)
+        startForegroundService(foregroundService)
+
         val preferences = PreferenceManager.getDefaultSharedPreferences(YuzuApplication.appContext)
         if (!preferences.getBoolean(Settings.PREF_MEMORY_WARNING_SHOWN, false)) {
             if (MemoryUtil.isLessThan(MemoryUtil.REQUIRED_MEMORY, MemoryUtil.totalMemory)) {
@@ -189,6 +196,12 @@ class EmulationActivity : AppCompatActivity(), SensorEventListener {
         stopMotionSensorListener()
     }
 
+    override fun onDestroy() {
+        super.onDestroy()
+        stopForegroundService(this)
+
+    }
+
     override fun onUserLeaveHint() {
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.S) {
             if (BooleanSetting.PICTURE_IN_PICTURE.getBoolean() && !isInPictureInPictureMode) {
@@ -511,6 +524,12 @@ class EmulationActivity : AppCompatActivity(), SensorEventListener {
     companion object {
         const val EXTRA_SELECTED_GAME = "SelectedGame"
 
+        fun stopForegroundService(activity: Activity) {
+            val startIntent = Intent(activity, ForegroundService::class.java)
+            startIntent.action = ForegroundService.ACTION_STOP
+            activity.startForegroundService(startIntent)
+        }
+
         fun launch(activity: AppCompatActivity, game: Game) {
             val launcher = Intent(activity, EmulationActivity::class.java)
             launcher.putExtra(EXTRA_SELECTED_GAME, game)

src/android/app/src/main/java/org/yuzu/yuzu_emu/ui/main/MainActivity.kt

@@ -48,6 +48,7 @@ import java.io.BufferedOutputStream
 import java.util.zip.ZipEntry
 import java.util.zip.ZipInputStream
 import androidx.core.content.edit
+import org.yuzu.yuzu_emu.activities.EmulationActivity
 import kotlin.text.compareTo
 
 class MainActivity : AppCompatActivity(), ThemeProvider {
@@ -188,6 +189,9 @@ class MainActivity : AppCompatActivity(), ThemeProvider {
             if (it) checkKeys()
         }
 
+        // Dismiss previous notifications (should not happen unless a crash occurred)
+        EmulationActivity.stopForegroundService(this)
+
         setInsets()
     }
 
@@ -293,6 +297,11 @@ class MainActivity : AppCompatActivity(), ThemeProvider {
         themeId = resId
     }
 
+    override fun onDestroy() {
+        EmulationActivity.stopForegroundService(this)
+        super.onDestroy()
+    }
+
     val getGamesDirectory =
         registerForActivityResult(ActivityResultContracts.OpenDocumentTree()) { result ->
             if (result != null) {

src/android/app/src/main/java/org/yuzu/yuzu_emu/utils/ForegroundService.kt

@@ -0,0 +1,79 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// Copyright 2023 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+package org.yuzu.yuzu_emu.utils
+
+import android.app.PendingIntent
+import android.app.Service
+import android.content.Intent
+import android.os.IBinder
+import androidx.core.app.NotificationCompat
+import androidx.core.app.NotificationManagerCompat
+import org.yuzu.yuzu_emu.R
+import org.yuzu.yuzu_emu.activities.EmulationActivity
+
+/**
+ * A service that shows a permanent notification in the background to avoid the app getting
+ * cleared from memory by the system.
+ */
+class ForegroundService : Service() {
+    companion object {
+        const val EMULATION_RUNNING_NOTIFICATION = 0x1000
+
+        const val ACTION_STOP = "stop"
+    }
+
+    private fun showRunningNotification() {
+        // Intent is used to resume emulation if the notification is clicked
+        val contentIntent = PendingIntent.getActivity(
+            this,
+            0,
+            Intent(this, EmulationActivity::class.java),
+            PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT
+        )
+        val builder =
+            NotificationCompat.Builder(this, getString(R.string.app_notification_channel_id))
+                .setSmallIcon(R.drawable.ic_stat_notification_logo)
+                .setContentTitle(getString(R.string.app_name))
+                .setContentText(getString(R.string.app_notification_running))
+                .setPriority(NotificationCompat.PRIORITY_DEFAULT)
+                .setOngoing(true)
+                .setVibrate(null)
+                .setSound(null)
+                .setContentIntent(contentIntent)
+        startForeground(EMULATION_RUNNING_NOTIFICATION, builder.build())
+    }
+
+    override fun onBind(intent: Intent): IBinder? {
+        return null
+    }
+
+    override fun onCreate() {
+        showRunningNotification()
+    }
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
+        if (intent?.action == ACTION_STOP) {
+            try {
+                NotificationManagerCompat.from(this).cancel(EMULATION_RUNNING_NOTIFICATION)
+                stopForeground(STOP_FOREGROUND_REMOVE)
+            } catch (e: Exception) {
+                Log.error("Failed to stop foreground service")
+            }
+            stopSelfResult(startId)
+            return START_NOT_STICKY
+        }
+
+        if (intent != null) {
+            showRunningNotification()
+        }
+        return START_STICKY
+    }
+
+    override fun onDestroy() =
+        NotificationManagerCompat.from(this).cancel(EMULATION_RUNNING_NOTIFICATION)
+}

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

@@ -8,6 +8,11 @@
     <string name="notice_notification_channel_id" translatable="false">noticesAndErrors</string>
     <string name="notice_notification_channel_description">Shows notifications when something goes wrong.</string>
     <string name="notification_permission_not_granted">Notification permission not granted!</string>
+    <string name="app_notification_channel_name" translatable="false">Eden</string>
+    <string name="app_notification_channel_id" translatable="false">Eden</string>
+    <string name="app_notification_channel_description">Eden Switch emulator notifications</string>
+    <string name="app_notification_running">Eden is Running</string>
+
 
     <!-- Stats Overlay settings -->
     <string name="enhanced_fps_suffix">(Enhanced)</string>