Work around widget flickering

core/src/main/java/de/danoeh/antennapod/core/receiver/PlayerWidget.java

@@ -2,16 +2,22 @@ package de.danoeh.antennapod.core.receiver;
 
 import android.appwidget.AppWidgetManager;
 import android.appwidget.AppWidgetProvider;
+import android.content.ComponentName;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.util.Log;
+import androidx.work.ExistingWorkPolicy;
+import androidx.work.OneTimeWorkRequest;
+import androidx.work.WorkManager;
 import de.danoeh.antennapod.core.widget.WidgetUpdaterWorker;
 
 import java.util.Arrays;
+import java.util.concurrent.TimeUnit;
 
 public class PlayerWidget extends AppWidgetProvider {
     private static final String TAG = "PlayerWidget";
     public static final String PREFS_NAME = "PlayerWidgetPrefs";
+    private static final String KEY_WORKAROUND_ENABLED = "WorkaroundEnabled";
     private static final String KEY_ENABLED = "WidgetEnabled";
     public static final String KEY_WIDGET_COLOR = "widget_color";
     public static final String KEY_WIDGET_PLAYBACK_SPEED = "widget_playback_speed";
@@ -19,6 +25,7 @@ public class PlayerWidget extends AppWidgetProvider {
     public static final String KEY_WIDGET_FAST_FORWARD = "widget_fast_forward";
     public static final String KEY_WIDGET_REWIND = "widget_rewind";
     public static final int DEFAULT_COLOR = 0x00262C31;
+    private static final String WORKAROUND_WORK_NAME = "WidgetUpdaterWorkaround";
 
     @Override
     public void onEnabled(Context context) {
@@ -26,6 +33,7 @@ public class PlayerWidget extends AppWidgetProvider {
         Log.d(TAG, "Widget enabled");
         setEnabled(context, true);
         WidgetUpdaterWorker.enqueueWork(context);
+        scheduleWorkaround(context);
     }
 
     @Override
@@ -33,6 +41,12 @@ public class PlayerWidget extends AppWidgetProvider {
         Log.d(TAG, "onUpdate() called with: " + "context = [" + context + "], appWidgetManager = ["
                 + appWidgetManager + "], appWidgetIds = [" + Arrays.toString(appWidgetIds) + "]");
         WidgetUpdaterWorker.enqueueWork(context);
+
+        SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
+        if (!prefs.getBoolean(KEY_WORKAROUND_ENABLED, false)) {
+            scheduleWorkaround(context);
+            prefs.edit().putBoolean(KEY_WORKAROUND_ENABLED, true).apply();
+        }
     }
 
     @Override
@@ -45,17 +59,34 @@ public class PlayerWidget extends AppWidgetProvider {
     @Override
     public void onDeleted(Context context, int[] appWidgetIds) {
         Log.d(TAG, "OnDeleted");
+        SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
         for (int appWidgetId : appWidgetIds) {
-            SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
             prefs.edit().remove(KEY_WIDGET_COLOR + appWidgetId).apply();
             prefs.edit().remove(KEY_WIDGET_PLAYBACK_SPEED + appWidgetId).apply();
             prefs.edit().remove(KEY_WIDGET_REWIND + appWidgetId).apply();
             prefs.edit().remove(KEY_WIDGET_FAST_FORWARD + appWidgetId).apply();
             prefs.edit().remove(KEY_WIDGET_SKIP + appWidgetId).apply();
         }
+        AppWidgetManager manager = AppWidgetManager.getInstance(context);
+        int[] widgetIds = manager.getAppWidgetIds(new ComponentName(context, PlayerWidget.class));
+        if (widgetIds.length == 0) {
+            prefs.edit().putBoolean(KEY_WORKAROUND_ENABLED, false).apply();
+            WorkManager.getInstance(context).cancelUniqueWork(WORKAROUND_WORK_NAME);
+        }
         super.onDeleted(context, appWidgetIds);
     }
 
+    private static void scheduleWorkaround(Context context) {
+        // Enqueueing work enables a BOOT_COMPLETED receiver, which in turn makes Android refresh widgets.
+        // This creates an endless loop with a flickering widget.
+        // Workaround: When there is a widget, schedule a dummy task in the far future, so that the receiver stays.
+        final OneTimeWorkRequest workRequest = new OneTimeWorkRequest.Builder(WidgetUpdaterWorker.class)
+                .setInitialDelay(100 * 356, TimeUnit.DAYS)
+                .build();
+        WorkManager.getInstance(context)
+                .enqueueUniqueWork(WORKAROUND_WORK_NAME, ExistingWorkPolicy.REPLACE, workRequest);
+    }
+
     public static boolean isEnabled(Context context) {
         SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
         return prefs.getBoolean(KEY_ENABLED, false);