feat(android): implement POST_NOTIFICATIONS permission handling

Add NotificationSys to manage system notifications and update
MainActivity to request POST_NOTIFICATIONS permission on Android 13+.
Includes localized string resources for notification testing and
permission error feedback.

app/src/main/AndroidManifest.xml

@@ -9,10 +9,12 @@
         android:required="false" />
 
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
-    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" 
+        tools:ignore="ForegroundServicesPolicy" />
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PLAYBACK" />
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.WAKE_LOCK" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
 
     <application
         android:name=".Radio"

app/src/main/java/com/michatec/radio/MainActivity.kt

@@ -1,5 +1,7 @@
 package com.michatec.radio
 
+import android.Manifest
+import android.os.Build
 import android.content.Context
 import android.content.SharedPreferences
 import android.content.pm.PackageManager
@@ -13,6 +15,8 @@ import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.widget.Toolbar
 import androidx.core.view.isVisible
 import androidx.navigation.fragment.NavHostFragment
+import androidx.activity.result.contract.ActivityResultContracts
+import com.google.android.material.snackbar.Snackbar
 import androidx.navigation.ui.AppBarConfiguration
 import androidx.navigation.ui.NavigationUI
 import androidx.navigation.ui.navigateUp
@@ -31,6 +35,25 @@ class MainActivity : AppCompatActivity() {
     /* Main class variables */
     private lateinit var appBarConfiguration: AppBarConfiguration
 
+    // request notification permission (for Android 13+)
+    private val permissionLauncher = registerForActivityResult(
+        ActivityResultContracts.RequestPermission()
+    ) { isGranted ->
+        if (isGranted) {
+            NotificationSys.showNotification(
+                this, 
+                R.string.app_name, 
+                R.string.notification_test_content
+            )
+        } else {
+            Snackbar.make(
+                findViewById(android.R.id.content),
+                R.string.snackbar_failed_permission_notification, 
+                Snackbar.LENGTH_LONG
+            ).show()
+        }
+    }
+
     /* Overrides attachBaseContext from AppCompatActivity */
     override fun attachBaseContext(newBase: Context) {
         val languageCode = PreferencesHelper.loadSelectedLanguage()
@@ -82,6 +105,17 @@ class MainActivity : AppCompatActivity() {
 
         // register listener for changes in shared preferences
         PreferencesHelper.registerPreferenceChangeListener(sharedPreferenceChangeListener)
+
+        // request permissions
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            permissionLauncher.launch(Manifest.permission.POST_NOTIFICATIONS)
+        } else {
+            NotificationSys.showNotification(
+                this, 
+                R.string.app_name, 
+                R.string.notification_test_content
+            )
+        }
     }
 
     /* Hides the loading/splash overlay */

app/src/main/java/com/michatec/radio/NotificationSys.kt

@@ -0,0 +1,63 @@
+package com.michatec.radio
+
+import androidx.core.app.NotificationCompat
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.content.Context
+import android.content.Intent
+import com.michatec.radio.R
+
+object NotificationSys {
+    private const val CHANNEL_ID = "com.michatec.radio.channel"
+    private const val CHANNEL_NAME = "Notifications"
+    private const val NOTIFICATION_ID = 1001
+
+    fun createNotificationChannel(context: Context) {
+        val notificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
+
+        if (notificationManager.getNotificationChannel(CHANNEL_ID) == null) {
+            val channel = NotificationChannel(
+                CHANNEL_ID, 
+                CHANNEL_NAME, 
+                NotificationManager.IMPORTANCE_DEFAULT
+            ).apply {
+                description = context.getString(R.string.notification_channel_description)
+            }
+            notificationManager.createNotificationChannel(channel)
+        }
+    }
+
+    fun showNotification(context: Context, title: String, content: String) {
+        val notificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
+        createNotificationChannel(context)
+
+        val intent = Intent(context, MainActivity::class.java).apply {
+            flags = Intent.FLAG_ACTIVITY_CLEAR_TOP or Intent.FLAG_ACTIVITY_SINGLE_TOP
+        }
+
+        val pendingIntent = PendingIntent.getActivity(
+            context, 
+            0, 
+            intent, 
+            PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
+        )
+
+        val notification = NotificationCompat.Builder(context, CHANNEL_ID)
+            .setSmallIcon(R.drawable.ic_notification_app_icon_white_24dp)
+            .setContentTitle(title)
+            .setContentText(content)
+            .setPriority(NotificationCompat.PRIORITY_DEFAULT)
+            .setContentIntent(pendingIntent)
+            .setAutoCancel(true)
+            .build()
+
+        notificationManager.notify(NOTIFICATION_ID, notification)
+    }
+
+    fun showNotification(context: Context, titleResId: Int, contentResId: Int) {
+        val title = context.getString(titleResId)
+        val content = context.getString(contentResId)
+        showNotification(context, title, content)
+    }
+}

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

@@ -44,6 +44,7 @@
     <string name="notification_stop">Stop</string>
     <string name="notification_skip_to_previous">Forrige</string>
     <string name="notification_skip_to_next">Næste</string>
+    <string name="notification_test_content">Dette er en testmeddelelse.</string>
     <!-- Onboarding -->
     <string name="onboarding_app_description">Fordyb dig i lyden du elsker!</string>
     <string name="onboarding_app_get_started">Kom i gang</string>
@@ -111,6 +112,7 @@
     <!-- Snackbars -->
     <string name="snackbar_show">Vis</string>
     <string name="snackbar_update_available">er tilgængelig!</string>
+    <string name="snackbar_failed_permission_notification">Kunne ikke anmode om meddelelsestilladelse.</string>
     <!-- Language Selection -->
     <string name="pref_language_selection_title">Sprog</string>
     <string name="pref_language_selection_summary">Aktuelt sprog</string>

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

@@ -44,6 +44,7 @@
     <string name="notification_stop">Stopp</string>
     <string name="notification_skip_to_previous">Zurück</string>
     <string name="notification_skip_to_next">Nächste</string>
+    <string name="notification_test_content">Dies ist eine Testbenachrichtigung.</string>
     <!-- Onboarding -->
     <string name="onboarding_app_description">Tauche ein in den Sound deiner Wahl!</string>
     <string name="onboarding_app_get_started">Jetzt starten</string>
@@ -122,6 +123,7 @@
     <!-- Snackbars -->
     <string name="snackbar_show">Zeigen</string>
     <string name="snackbar_update_available">ist verfügbar!</string>
+    <string name="snackbar_failed_permission_notification">Fehler bei der Anfrage nach Benachrichtigungsberechtigung.</string>
     <string name="pref_audio_effects_title">Audio-Effekte</string>
     <string name="pref_bass_boost_title">Bass-Boost</string>
     <string name="pref_bass_boost_summary">Erhöhen Sie die Bassverstärkung.</string>

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

@@ -44,6 +44,7 @@
     <string name="notification_stop">Διακοπή</string>
     <string name="notification_skip_to_previous">Προηγούμενο</string>
     <string name="notification_skip_to_next">Επόμενο</string>
+    <string name="notification_test_content">Αυτή είναι μια δοκιμαστική ειδοποίηση.</string>
     <!-- Onboarding -->
     <string name="onboarding_app_description">Βυθιστείτε στον ήχο της επιλογής σας!</string>
     <string name="onboarding_app_get_started">Ας ξεκινήσουμε</string>
@@ -113,6 +114,7 @@
     <!-- Snackbars -->
     <string name="snackbar_show">Εμφάνισε</string>
     <string name="snackbar_update_available">είναι διαθέσιμη!</string>
+    <string name="snackbar_failed_permission_notification">Απέτυχε η αίτηση δικαιώματος ειδοποίησης.</string>
     <!-- Language Selection -->
     <string name="pref_language_selection_title">Γλώσσα</string>
     <string name="pref_language_selection_summary">Τρέχουσα γλώσσα</string>

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

@@ -44,6 +44,7 @@
     <string name="notification_stop">Arrêt</string>
     <string name="notification_skip_to_previous">Précédent</string>
     <string name="notification_skip_to_next">Suivant</string>
+    <string name="notification_test_content">Il s'agit d'une notification de test.</string>
     <!-- Onboarding -->
     <string name="onboarding_app_description">Plongez dans le son de votre choix !</string>
     <string name="onboarding_app_get_started">Commencer maintenant</string>
@@ -111,6 +112,7 @@
     <!-- Snackbars -->
     <string name="snackbar_show">Afficher</string>
     <string name="snackbar_update_available">est disponible !</string>
+    <string name="snackbar_failed_permission_notification">Échec de la demande d'autorisation de notification.</string>
     <!-- Language Selection -->
     <string name="pref_language_selection_title">Langue</string>
     <string name="pref_language_selection_summary">Langue actuelle</string>

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

@@ -44,6 +44,7 @@
     <string name="notification_stop">停止</string>
     <string name="notification_skip_to_previous">前へ</string>
     <string name="notification_skip_to_next">次へ</string>
+    <string name="notification_test_content">テスト通知です。</string>
     <!-- オンボーディング -->
     <string name="onboarding_app_description">お気に入りのサウンドの世界に飛び込もう！</string>
     <string name="onboarding_app_get_started">今すぐ始める</string>
@@ -112,6 +113,7 @@
     <!-- スナックバー -->
     <string name="snackbar_show">表示</string>
     <string name="snackbar_update_available">が利用可能です！</string>
+    <string name="snackbar_failed_permission_notification">通知の権限リクエストに失敗しました。</string>
     <!-- 言語選択 -->
     <string name="pref_language_selection_title">言語</string>
     <string name="pref_language_selection_summary">現在の言語</string>

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

@@ -44,6 +44,7 @@
     <string name="notification_stop">Stoppen</string>
     <string name="notification_skip_to_previous">Vorige</string>
     <string name="notification_skip_to_next">Volgende</string>
+    <string name="notification_test_content">Dit is een testmelding.</string>
     <!-- Onboarding -->
     <string name="onboarding_app_description">Dompel jezelf onder in het geluid van je keuze!</string>
     <string name="onboarding_app_get_started">Aan de slag</string>
@@ -113,6 +114,7 @@
     <!-- Snackbars -->
     <string name="snackbar_show">Weergeven</string>
     <string name="snackbar_update_available">is beschikbaar!</string>
+    <string name="snackbar_failed_permission_notification">Kan notificatierechtiging niet aanvragen.</string>
     <!-- Language Selection -->
     <string name="pref_language_selection_title">Taal</string>
     <string name="pref_language_selection_summary">Huidige taal</string>

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

@@ -44,6 +44,7 @@
     <string name="notification_stop">Zatrzymaj</string>
     <string name="notification_skip_to_previous">Poprzedni</string>
     <string name="notification_skip_to_next">Następny</string>
+    <string name="notification_test_content">To jest powiadomienie testowe.</string>
     <!-- Onboarding -->
     <string name="onboarding_app_description">Zanurz się w dźwięku swojego wyboru!</string>
     <string name="onboarding_app_get_started">Zaczynamy</string>
@@ -113,6 +114,7 @@
     <!-- Snackbars -->
     <string name="snackbar_show">Wyświetl</string>
     <string name="snackbar_update_available">jest dostępna!</string>
+    <string name="snackbar_failed_permission_notification">Nie udało się poprosić o pozwolenie na powiadomienia.</string>
     <!-- Language Selection -->
     <string name="pref_language_selection_title">Język</string>
     <string name="pref_language_selection_summary">Aktualny język</string>

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

@@ -44,6 +44,7 @@
     <string name="notification_stop">Остановить</string>
     <string name="notification_skip_to_previous">Предыдущий</string>
     <string name="notification_skip_to_next">Следующий</string>
+    <string name="notification_test_content">Это тестовое уведомление.</string>
     <!-- Onboarding -->
     <string name="onboarding_app_description">Погрузитесь в звук по вашему выбору!</string>
     <string name="onboarding_app_get_started">Начать</string>
@@ -113,6 +114,7 @@
     <!-- Snackbars -->
     <string name="snackbar_show">Показать</string>
     <string name="snackbar_update_available">доступно!</string>
+    <string name="snackbar_failed_permission_notification">Не удалось запросить разрешение на уведомления.</string>
     <!-- Language Selection -->
     <string name="pref_language_selection_title">Язык</string>
     <string name="pref_language_selection_summary">Текущий язык</string>

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

@@ -44,6 +44,7 @@
     <string name="notification_stop">Зупинити</string>
     <string name="notification_skip_to_previous">Попередня</string>
     <string name="notification_skip_to_next">Наступна</string>
+    <string name="notification_test_content">Це тестове сповіщення.</string>
     <!-- Onboarding -->
     <string name="onboarding_app_description">Пориньте у звук на ваш вибір!</string>
     <string name="onboarding_app_get_started">Початок роботи</string>
@@ -113,6 +114,7 @@
     <!-- Snackbars -->
     <string name="snackbar_show">Показати</string>
     <string name="snackbar_update_available">доступне!</string>
+    <string name="snackbar_failed_permission_notification">Не вдалося запитати дозвіл на сповіщення.</string>
     <!-- Language Selection -->
     <string name="pref_language_selection_title">Мова</string>
     <string name="pref_language_selection_summary">Поточна мова</string>

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

@@ -2,6 +2,7 @@
 <resources>
     <!-- App Name -->
     <string name="app_version_name" translatable="false">\"Red\"</string>
+    <string name="app_name" translatable="false">Radio</string>
 
     <!-- Accessibility Descriptions -->
     <string name="descr_app_icon">App icon depicting an old radio</string>
@@ -49,6 +50,7 @@
     <string name="notification_stop">Stop</string>
     <string name="notification_skip_to_previous">Previous</string>
     <string name="notification_skip_to_next">Next</string>
+    <string name="notification_test_content">This is a test notification.</string>
 
     <!-- Onboarding -->
     <string name="onboarding_app_description">Immerse yourself in the sound of your choice!</string>
@@ -184,8 +186,8 @@
     <string name="snackbar_update_available">is available!</string>
     <string name="snackbar_url_app_home_page" translatable="false">https://github.com/michatec/Radio/releases/latest</string>
     <string name="snackbar_github_update_check_url" translatable="false">https://api.github.com/repos/michatec/Radio/releases/latest</string>
-    <string name="app_name" translatable="false">Radio</string>
     <string name="icon_launcher" translatable="false">Icon launcher.</string>
+    <string name="snackbar_failed_permission_notification">Failed to request notification permission.</string>
 
     <!-- Extras -->
     <string name="loading">Loading…</string>