Show notifications from workers (#3760)

Fix a crash where workers, in some conditions, should show a notification. These are sent to a dedicated channel with no importance.

Convert NotificationWorker to a CoroutineWorker and remove its use of `runBlocking`.

Fixes #3754

app/lint-baseline.xml

@@ -80,7 +80,7 @@
         errorLine2="                    ~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/compose/ComposeViewModel.kt"
-            line="254"
+            line="280"
             column="21"/>
     </issue>
 
@@ -791,22 +791,22 @@
     <issue
         id="ImpliedQuantity"
         message="The quantity `&apos;one&apos;` matches more than one specific number in this locale (0, 1), but the message did not \&#xA;include a formatting argument (such as `%d`). This is usually an internationalization error. See full issue \&#xA;explanation for more."
-        errorLine1="        &lt;item quantity=&quot;one&quot;>توصیف محتوا برای کم‌بینایان (کران ۱ نویسه)&lt;/item>"
-        errorLine2="        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
+        errorLine1="        &lt;item quantity=&quot;one&quot;>برهم‌کنشی جدید&lt;/item>"
+        errorLine2="        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values-fa/strings.xml"
-            line="232"
+            line="193"
             column="9"/>
     </issue>
 
     <issue
         id="ImpliedQuantity"
         message="The quantity `&apos;one&apos;` matches more than one specific number in this locale (0, 1), but the message did not \&#xA;include a formatting argument (such as `%d`). This is usually an internationalization error. See full issue \&#xA;explanation for more."
-        errorLine1="        &lt;item quantity=&quot;one&quot;>۱ برگزیدن&lt;/item>"
-        errorLine2="        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
+        errorLine1="        &lt;item quantity=&quot;one&quot;>توصیف محتوا برای کم‌بینایان (کران ۱ نویسه)&lt;/item>"
+        errorLine2="        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values-fa/strings.xml"
-            line="342"
+            line="232"
             column="9"/>
     </issue>
 
@@ -839,7 +839,7 @@
         errorLine2="    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="376"
+            line="378"
             column="5"/>
     </issue>
 
@@ -850,7 +850,7 @@
         errorLine2="    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="552"
+            line="557"
             column="5"/>
     </issue>
 
@@ -861,7 +861,7 @@
         errorLine2="    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="773"
+            line="777"
             column="5"/>
     </issue>
 
@@ -1532,7 +1532,7 @@
         errorLine2="        ~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/adapter/AccountFieldEditAdapter.kt"
-            line="42"
+            line="43"
             column="9"/>
     </issue>
 
@@ -1543,7 +1543,7 @@
         errorLine2="        ~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/adapter/AccountFieldEditAdapter.kt"
-            line="48"
+            line="49"
             column="9"/>
     </issue>
 
@@ -1653,7 +1653,7 @@
         errorLine2="                                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="826"
+            line="877"
             column="57"/>
     </issue>
 
@@ -2500,7 +2500,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="387"
+            line="391"
             column="13"/>
     </issue>
 
@@ -2511,7 +2511,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="446"
+            line="450"
             column="13"/>
     </issue>
 
@@ -2522,7 +2522,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="497"
+            line="502"
             column="13"/>
     </issue>
 
@@ -2533,7 +2533,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="501"
+            line="506"
             column="13"/>
     </issue>
 
@@ -2544,7 +2544,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="502"
+            line="507"
             column="13"/>
     </issue>
 
@@ -2555,7 +2555,7 @@
         errorLine2="            ~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="503"
+            line="508"
             column="13"/>
     </issue>
 
@@ -2566,7 +2566,7 @@
         errorLine2="            ~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="504"
+            line="509"
             column="13"/>
     </issue>
 
@@ -2577,7 +2577,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="505"
+            line="510"
             column="13"/>
     </issue>
 
@@ -2588,7 +2588,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="506"
+            line="511"
             column="13"/>
     </issue>
 
@@ -2599,7 +2599,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="507"
+            line="512"
             column="13"/>
     </issue>
 
@@ -2610,7 +2610,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="508"
+            line="513"
             column="13"/>
     </issue>
 
@@ -2621,7 +2621,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="510"
+            line="515"
             column="13"/>
     </issue>
 
@@ -2632,7 +2632,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="595"
+            line="600"
             column="13"/>
     </issue>
 
@@ -2643,7 +2643,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="596"
+            line="601"
             column="13"/>
     </issue>
 
@@ -2654,7 +2654,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="610"
+            line="615"
             column="13"/>
     </issue>
 
@@ -2665,7 +2665,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="612"
+            line="617"
             column="13"/>
     </issue>
 
@@ -2676,7 +2676,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="613"
+            line="618"
             column="13"/>
     </issue>
 
@@ -2687,7 +2687,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="616"
+            line="621"
             column="13"/>
     </issue>
 
@@ -2698,7 +2698,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="661"
+            line="666"
             column="13"/>
     </issue>
 
@@ -2709,7 +2709,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="710"
+            line="715"
             column="13"/>
     </issue>
 
@@ -2720,7 +2720,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="716"
+            line="721"
             column="13"/>
     </issue>
 
@@ -2731,7 +2731,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="757"
+            line="762"
             column="13"/>
     </issue>
 
@@ -2742,7 +2742,7 @@
         errorLine2="            ~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="794"
+            line="798"
             column="13"/>
     </issue>
 
@@ -2940,7 +2940,7 @@
         errorLine2="                        ~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/preference/AccountPreferencesFragment.kt"
-            line="311"
+            line="310"
             column="25"/>
     </issue>
 
@@ -2951,7 +2951,7 @@
         errorLine2="                    ~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/preference/AccountPreferencesFragment.kt"
-            line="317"
+            line="316"
             column="21"/>
     </issue>
 
@@ -3116,7 +3116,7 @@
         errorLine2="                    ~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/compose/ComposeActivity.kt"
-            line="552"
+            line="553"
             column="21"/>
     </issue>
 
@@ -3127,7 +3127,7 @@
         errorLine2="                ~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/compose/ComposeActivity.kt"
-            line="561"
+            line="562"
             column="17"/>
     </issue>
 
@@ -3138,7 +3138,7 @@
         errorLine2="                ~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/compose/ComposeActivity.kt"
-            line="561"
+            line="562"
             column="17"/>
     </issue>
 
@@ -3226,7 +3226,7 @@
         errorLine2="                ~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/filters/EditFilterActivity.kt"
-            line="107"
+            line="113"
             column="17"/>
     </issue>
 
@@ -3237,7 +3237,7 @@
         errorLine2="                ~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/filters/EditFilterActivity.kt"
-            line="107"
+            line="113"
             column="17"/>
     </issue>
 
@@ -3248,7 +3248,7 @@
         errorLine2="                ~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/filters/EditFilterActivity.kt"
-            line="117"
+            line="123"
             column="17"/>
     </issue>
 
@@ -3259,7 +3259,7 @@
         errorLine2="                ~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/filters/EditFilterActivity.kt"
-            line="117"
+            line="123"
             column="17"/>
     </issue>
 
@@ -4425,7 +4425,7 @@
         errorLine2="                         ~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationsFragment.kt"
-            line="186"
+            line="187"
             column="26"/>
     </issue>
 
@@ -4436,7 +4436,7 @@
         errorLine2="                    ~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationsFragment.kt"
-            line="227"
+            line="228"
             column="21"/>
     </issue>
 
@@ -4447,7 +4447,7 @@
         errorLine2="                            ~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationsFragment.kt"
-            line="229"
+            line="230"
             column="29"/>
     </issue>
 
@@ -5096,7 +5096,7 @@
         errorLine2="                                                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/res/values/strings.xml"
-            line="743"
+            line="748"
             column="55"/>
     </issue>
 
@@ -6071,7 +6071,7 @@
         errorLine2="     ~~~~~~~~">
         <location
             file="src/main/res/layout/item_status_edit.xml"
-            line="24"
+            line="13"
             column="6"/>
     </issue>
 
@@ -6082,7 +6082,7 @@
         errorLine2="     ~~~~~~~~">
         <location
             file="src/main/res/layout/item_status_edit.xml"
-            line="74"
+            line="55"
             column="6"/>
     </issue>
 
@@ -6115,7 +6115,7 @@
         errorLine2="     ~~~~~~~~">
         <location
             file="src/main/res/layout/item_status_notification.xml"
-            line="71"
+            line="70"
             column="6"/>
     </issue>
 
@@ -6126,7 +6126,7 @@
         errorLine2="     ~~~~~~~~">
         <location
             file="src/main/res/layout/item_status_notification.xml"
-            line="85"
+            line="84"
             column="6"/>
     </issue>
 
@@ -6225,7 +6225,7 @@
         errorLine2="         ~~~~~~~~">
         <location
             file="src/main/res/layout-land/item_trending_cell.xml"
-            line="95"
+            line="94"
             column="10"/>
     </issue>
 
@@ -6236,7 +6236,7 @@
         errorLine2="         ~~~~~~~~">
         <location
             file="src/main/res/layout/item_trending_cell.xml"
-            line="95"
+            line="94"
             column="10"/>
     </issue>
 
@@ -6247,7 +6247,7 @@
         errorLine2="         ~~~~~~~~">
         <location
             file="src/main/res/layout-land/item_trending_cell.xml"
-            line="126"
+            line="125"
             column="10"/>
     </issue>
 
@@ -6258,7 +6258,7 @@
         errorLine2="         ~~~~~~~~">
         <location
             file="src/main/res/layout/item_trending_cell.xml"
-            line="127"
+            line="126"
             column="10"/>
     </issue>
 
@@ -6896,7 +6896,7 @@
         errorLine2="                                   ~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/BaseActivity.java"
-            line="240"
+            line="233"
             column="36"/>
     </issue>
 
@@ -6907,7 +6907,7 @@
         errorLine2="                                                         ~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/BaseActivity.java"
-            line="240"
+            line="233"
             column="58"/>
     </issue>
 
@@ -6918,7 +6918,7 @@
         errorLine2="                                                      ~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="151"
+            line="159"
             column="55"/>
     </issue>
 
@@ -6929,7 +6929,7 @@
         errorLine2="                                                                       ~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="151"
+            line="159"
             column="72"/>
     </issue>
 
@@ -6940,7 +6940,7 @@
         errorLine2="                                                                                                                ~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="151"
+            line="159"
             column="113"/>
     </issue>
 
@@ -6951,7 +6951,7 @@
         errorLine2="                                                                                                                                   ~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="151"
+            line="159"
             column="132"/>
     </issue>
 
@@ -6962,7 +6962,7 @@
         errorLine2="                                                  ~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="273"
+            line="281"
             column="51"/>
     </issue>
 
@@ -6973,7 +6973,7 @@
         errorLine2="                                                                   ~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="273"
+            line="281"
             column="68"/>
     </issue>
 
@@ -6984,7 +6984,7 @@
         errorLine2="                                                                                                            ~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="273"
+            line="281"
             column="109"/>
     </issue>
 
@@ -6995,7 +6995,7 @@
         errorLine2="                                               ~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="576"
+            line="627"
             column="48"/>
     </issue>
 
@@ -7006,7 +7006,7 @@
         errorLine2="                                                ~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="604"
+            line="655"
             column="49"/>
     </issue>
 
@@ -7017,7 +7017,7 @@
         errorLine2="                                             ~~~~~~~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="620"
+            line="671"
             column="46"/>
     </issue>
 
@@ -7028,7 +7028,7 @@
         errorLine2="                                                                                      ~~~~~~~~~~~~~">
         <location
             file="src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java"
-            line="620"
+            line="671"
             column="87"/>
     </issue>
 

app/src/main/java/com/keylesspalace/tusky/TuskyApplication.kt

@@ -23,6 +23,7 @@ import androidx.work.ExistingPeriodicWorkPolicy
 import androidx.work.PeriodicWorkRequestBuilder
 import androidx.work.WorkManager
 import autodispose2.AutoDisposePlugins
+import com.keylesspalace.tusky.components.notifications.NotificationHelper
 import com.keylesspalace.tusky.di.AppInjector
 import com.keylesspalace.tusky.settings.PrefKeys
 import com.keylesspalace.tusky.settings.SCHEMA_VERSION
@@ -95,6 +96,8 @@ class TuskyApplication : Application(), HasAndroidInjector {
             Log.w("RxJava", "undeliverable exception", it)
         }
 
+        NotificationHelper.createWorkerNotificationChannel(this)
+
         WorkManager.initialize(
             this,
             androidx.work.Configuration.Builder()

app/src/main/java/com/keylesspalace/tusky/components/notifications/NotificationFetcher.kt

@@ -11,9 +11,10 @@ import com.keylesspalace.tusky.entity.Marker
 import com.keylesspalace.tusky.entity.Notification
 import com.keylesspalace.tusky.network.MastodonApi
 import com.keylesspalace.tusky.util.isLessThan
-import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.delay
 import javax.inject.Inject
 import kotlin.math.min
+import kotlin.time.Duration.Companion.milliseconds
 
 /**
  * Fetch Mastodon notifications and show Android notifications, with summaries, for them.
@@ -29,19 +30,17 @@ class NotificationFetcher @Inject constructor(
     private val accountManager: AccountManager,
     private val context: Context
 ) {
-    fun fetchAndShow() {
+    suspend fun fetchAndShow() {
         for (account in accountManager.getAllAccountsOrderedByActive()) {
             if (account.notificationsEnabled) {
                 try {
                     val notificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
 
                     // Create sorted list of new notifications
-                    val notifications = runBlocking { // OK, because in a worker thread
-                        fetchNewNotifications(account)
-                            .filter { filterNotification(notificationManager, account, it) }
-                            .sortedWith(compareBy({ it.id.length }, { it.id })) // oldest notifications first
-                            .toMutableList()
-                    }
+                    val notifications = fetchNewNotifications(account)
+                        .filter { filterNotification(notificationManager, account, it) }
+                        .sortedWith(compareBy({ it.id.length }, { it.id })) // oldest notifications first
+                        .toMutableList()
 
                     // There's a maximum limit on the number of notifications an Android app
                     // can display. If the total number of notifications (current notifications,
@@ -82,7 +81,7 @@ class NotificationFetcher @Inject constructor(
                         // Android will rate limit / drop notifications if they're posted too
                         // quickly. There is no indication to the user that this happened.
                         // See https://github.com/tuskyapp/Tusky/pull/3626#discussion_r1192963664
-                        Thread.sleep(1000)
+                        delay(1000.milliseconds)
                     }
 
                     NotificationHelper.updateSummaryNotifications(

app/src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java

@@ -37,6 +37,7 @@ import android.util.Log;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.annotation.StringRes;
 import androidx.core.app.NotificationCompat;
 import androidx.core.app.RemoteInput;
 import androidx.core.app.TaskStackBuilder;
@@ -77,7 +78,12 @@ import java.util.concurrent.TimeUnit;
 
 public class NotificationHelper {
 
-    private static int notificationId = 0;
+    /** ID of notification shown when fetching notifications */
+    public static final int NOTIFICATION_ID_FETCH_NOTIFICATION = 0;
+    /** ID of notification shown when pruning the cache */
+    public static final int NOTIFICATION_ID_PRUNE_CACHE = 1;
+    /** Dynamic notification IDs start here */
+    private static int notificationId = NOTIFICATION_ID_PRUNE_CACHE + 1;
 
     /**
      * constants used in Intents
@@ -121,6 +127,7 @@ public class NotificationHelper {
     public static final String CHANNEL_SIGN_UP = "CHANNEL_SIGN_UP";
     public static final String CHANNEL_UPDATES = "CHANNEL_UPDATES";
     public static final String CHANNEL_REPORT = "CHANNEL_REPORT";
+    public static final String CHANNEL_BACKGROUND_TASKS = "CHANNEL_BACKGROUND_TASKS";
 
     /**
      * WorkManager Tag
@@ -472,6 +479,49 @@ public class NotificationHelper {
                 pendingIntentFlags(false));
     }
 
+    /**
+     * Creates a notification channel for notifications for background work that should not
+     * disturb the user.
+     *
+     * @param context context
+     */
+    public static void createWorkerNotificationChannel(@NonNull Context context) {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) return;
+
+        NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
+
+        NotificationChannel channel = new NotificationChannel(
+            CHANNEL_BACKGROUND_TASKS,
+            context.getString(R.string.notification_listenable_worker_name),
+            NotificationManager.IMPORTANCE_NONE
+        );
+
+        channel.setDescription(context.getString(R.string.notification_listenable_worker_description));
+        channel.enableLights(false);
+        channel.enableVibration(false);
+        channel.setShowBadge(false);
+
+        notificationManager.createNotificationChannel(channel);
+    }
+
+    /**
+     * Creates a notification for a background worker.
+     *
+     * @param context context
+     * @param titleResource String resource to use as the notification's title
+     * @return the notification
+     */
+    @NonNull
+    public static android.app.Notification createWorkerNotification(@NonNull Context context, @StringRes int titleResource) {
+        String title = context.getString(titleResource);
+        return new NotificationCompat.Builder(context, CHANNEL_BACKGROUND_TASKS)
+            .setContentTitle(title)
+            .setTicker(title)
+            .setSmallIcon(R.drawable.ic_notify)
+            .setOngoing(true)
+            .build();
+    }
+
     public static void createNotificationChannelsForAccount(@NonNull AccountEntity account, @NonNull Context context) {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
 

app/src/main/java/com/keylesspalace/tusky/worker/NotificationWorker.kt

@@ -17,10 +17,15 @@
 
 package com.keylesspalace.tusky.worker
 
+import android.app.Notification
 import android.content.Context
-import androidx.work.Worker
+import androidx.work.CoroutineWorker
+import androidx.work.ForegroundInfo
 import androidx.work.WorkerParameters
+import com.keylesspalace.tusky.R
 import com.keylesspalace.tusky.components.notifications.NotificationFetcher
+import com.keylesspalace.tusky.components.notifications.NotificationHelper
+import com.keylesspalace.tusky.components.notifications.NotificationHelper.NOTIFICATION_ID_FETCH_NOTIFICATION
 import javax.inject.Inject
 
 /** Fetch and show new notifications. */
@@ -28,16 +33,20 @@ class NotificationWorker(
     appContext: Context,
     params: WorkerParameters,
     private val notificationsFetcher: NotificationFetcher
-) : Worker(appContext, params) {
-    override fun doWork(): Result {
+) : CoroutineWorker(appContext, params) {
+    val notification: Notification = NotificationHelper.createWorkerNotification(applicationContext, R.string.notification_notification_worker)
+
+    override suspend fun doWork(): Result {
         notificationsFetcher.fetchAndShow()
         return Result.success()
     }
 
+    override suspend fun getForegroundInfo() = ForegroundInfo(NOTIFICATION_ID_FETCH_NOTIFICATION, notification)
+
     class Factory @Inject constructor(
         private val notificationsFetcher: NotificationFetcher
     ) : ChildWorkerFactory {
-        override fun createWorker(appContext: Context, params: WorkerParameters): Worker {
+        override fun createWorker(appContext: Context, params: WorkerParameters): CoroutineWorker {
             return NotificationWorker(appContext, params, notificationsFetcher)
         }
     }

app/src/main/java/com/keylesspalace/tusky/worker/PruneCacheWorker.kt

@@ -17,11 +17,16 @@
 
 package com.keylesspalace.tusky.worker
 
+import android.app.Notification
 import android.content.Context
 import android.util.Log
 import androidx.work.CoroutineWorker
+import androidx.work.ForegroundInfo
 import androidx.work.ListenableWorker
 import androidx.work.WorkerParameters
+import com.keylesspalace.tusky.R
+import com.keylesspalace.tusky.components.notifications.NotificationHelper
+import com.keylesspalace.tusky.components.notifications.NotificationHelper.NOTIFICATION_ID_PRUNE_CACHE
 import com.keylesspalace.tusky.db.AccountManager
 import com.keylesspalace.tusky.db.AppDatabase
 import javax.inject.Inject
@@ -33,6 +38,8 @@ class PruneCacheWorker(
     private val appDatabase: AppDatabase,
     private val accountManager: AccountManager
 ) : CoroutineWorker(appContext, workerParams) {
+    val notification: Notification = NotificationHelper.createWorkerNotification(applicationContext, R.string.notification_prune_cache)
+
     override suspend fun doWork(): Result {
         for (account in accountManager.accounts) {
             Log.d(TAG, "Pruning database using account ID: ${account.id}")
@@ -41,6 +48,8 @@ class PruneCacheWorker(
         return Result.success()
     }
 
+    override suspend fun getForegroundInfo() = ForegroundInfo(NOTIFICATION_ID_PRUNE_CACHE, notification)
+
     companion object {
         private const val TAG = "PruneCacheWorker"
         private const val MAX_STATUSES_IN_CACHE = 1000

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

@@ -371,6 +371,8 @@
     <string name="notification_update_description">Notifications when posts you\'ve interacted with are edited</string>
     <string name="notification_report_name">Reports</string>
     <string name="notification_report_description">Notifications about moderation reports</string>
+    <string name="notification_listenable_worker_name">Background activity</string>
+    <string name="notification_listenable_worker_description">Notifications when Tusky is working in the background</string>
     <string name="notification_unknown_name">Unknown</string>
 
     <string name="notification_mention_format">%s mentioned you</string>
@@ -381,6 +383,8 @@
         <item quantity="one">%d new interaction</item>
         <item quantity="other">%d new interactions</item>
     </plurals>
+    <string name="notification_notification_worker">Fetching notifications…</string>
+    <string name="notification_prune_cache">Cache maintenance…</string>
 
     <string name="description_account_locked">Locked Account</string>