Use executors for more control over started threads

Signed-off-by: Stefan Niedermann <info@niedermann.it>

9 files changed, 102 insertions, 69 deletions

diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/LiveDataHelper.java b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/LiveDataHelper.java
index 10a18bb09..059ed5e6b 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/LiveDataHelper.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/LiveDataHelper.java
@@ -6,38 +6,24 @@ import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MediatorLiveData;
 import androidx.lifecycle.Observer;
 
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
 import static androidx.lifecycle.Transformations.distinctUntilChanged;
 
 public class LiveDataHelper {
 
-    public interface DataChangeProcessor<T> {
-        void onDataChanged(T data);
+    private LiveDataHelper() {
+        throw new UnsupportedOperationException("This class must not be instantiated.");
     }
 
-    public interface DataTransformator<I, O> {
-        O transform(I data);
-    }
-
-    public interface LiveDataWrapper<T> {
-        T getData();
-
-        default void postResult(WrappedLiveData<T> liveData) {
-            liveData.setError(null);
-            T data = null;
-            try {
-                data = getData();
-            } catch (RuntimeException e) {
-                liveData.setError(e);
-            }
-            liveData.postValue(data);
-        }
-    }
+    private static final ExecutorService executor = Executors.newCachedThreadPool();
 
     public static <T> LiveData<T> interceptLiveData(LiveData<T> data, DataChangeProcessor<T> onDataChange) {
         MediatorLiveData<T> ret = new MediatorLiveData<>();
 
         ret.addSource(data, changedData ->
-                doAsync(() -> {
+                executor.submit(() -> {
                     onDataChange.onDataChanged(changedData);
                     ret.postValue(changedData);
                 })
@@ -47,32 +33,29 @@ public class LiveDataHelper {
 
 
     public static <I, O> LiveData<O> postCustomValue(LiveData<I> data, DataTransformator<I, O> transformator) {
-        MediatorLiveData<O> ret = new MediatorLiveData<>();
-
-        ret.addSource(data, changedData -> doAsync(() -> ret.postValue(transformator.transform(changedData))));
+        final MediatorLiveData<O> ret = new MediatorLiveData<>();
+        ret.addSource(data, changedData -> executor.submit(() -> ret.postValue(transformator.transform(changedData))));
         return distinctUntilChanged(ret);
     }
 
     public static <I> MediatorLiveData<I> of(I oneShot) {
-        MediatorLiveData<I> ret = new MediatorLiveData<I>() {
+        return new MediatorLiveData<I>() {
             @Override
             public void observe(@NonNull LifecycleOwner owner, @NonNull Observer observer) {
                 super.observe(owner, observer);
-                doAsync(() -> postValue(oneShot));
+                executor.submit(() -> postValue(oneShot));
             }
         };
-        return ret;
     }
 
     public static <I, O> LiveData<O> postSingleValue(LiveData<I> data, DataTransformator<I, O> transformator) {
-        MediatorLiveData<O> ret = new MediatorLiveData<>();
-
-        ret.addSource(data, changedData -> doAsync(() -> ret.postValue(transformator.transform(changedData))));
+        final MediatorLiveData<O> ret = new MediatorLiveData<>();
+        ret.addSource(data, changedData -> executor.submit(() -> ret.postValue(transformator.transform(changedData))));
         return distinctUntilChanged(ret);
     }
 
     public static <T> void observeOnce(LiveData<T> liveData, LifecycleOwner owner, Observer<T> observer) {
-        Observer<T> tempObserver = new Observer<T>() {
+        final Observer<T> tempObserver = new Observer<T>() {
             @Override
             public void onChanged(T result) {
                 liveData.removeObserver(this);
@@ -85,7 +68,7 @@ public class LiveDataHelper {
     public static <T> WrappedLiveData<T> wrapInLiveData(final LiveDataWrapper<T> liveDataWrapper) {
         final WrappedLiveData<T> liveData = new WrappedLiveData<>();
 
-        doAsync(() -> {
+        executor.submit(() -> {
             try {
                 liveDataWrapper.postResult(liveData);
             } catch (Throwable t) {
@@ -96,7 +79,26 @@ public class LiveDataHelper {
         return liveData;
     }
 
-    private static void doAsync(Runnable r) {
-        new Thread(r).start();
+    public interface DataChangeProcessor<T> {
+        void onDataChanged(T data);
+    }
+
+    public interface DataTransformator<I, O> {
+        O transform(I data);
+    }
+
+    public interface LiveDataWrapper<T> {
+        T getData();
+
+        default void postResult(WrappedLiveData<T> liveData) {
+            liveData.setError(null);
+            T data = null;
+            try {
+                data = getData();
+            } catch (RuntimeException e) {
+                liveData.setError(e);
+            }
+            liveData.postValue(data);
+        }
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/extrawurst/UserSearchLiveData.java b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/extrawurst/UserSearchLiveData.java
index 3d05247b3..4a90664c9 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/extrawurst/UserSearchLiveData.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/extrawurst/UserSearchLiveData.java
@@ -18,12 +18,12 @@ import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.DataBaseAdapter
 public class UserSearchLiveData extends MediatorLiveData<List<User>> implements Debouncer.Callback<Long> {
 
     private static final int DEBOUNCE_TIME = 300; // ms
-    private DataBaseAdapter db;
-    private ServerAdapter server;
+    private final DataBaseAdapter db;
+    private final ServerAdapter server;
     long accountId;
     String searchTerm;
     long notYetAssignedInACL;
-    private Debouncer<Long> debouncer = new Debouncer<>(this, DEBOUNCE_TIME);
+    private final Debouncer<Long> debouncer = new Debouncer<>(this, DEBOUNCE_TIME);
 
     public UserSearchLiveData(DataBaseAdapter db, ServerAdapter server) {
         this.db = db;
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/CardAdapter.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/CardAdapter.java
index f1f584df6..4648e34c3 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/CardAdapter.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/CardAdapter.java
@@ -19,6 +19,8 @@ import androidx.recyclerview.widget.RecyclerView;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import it.niedermann.android.crosstabdnd.DragAndDropAdapter;
 import it.niedermann.android.crosstabdnd.DraggedItemLocalState;
@@ -45,6 +47,7 @@ import static it.niedermann.nextcloud.deck.util.MimeTypeUtil.TEXT_PLAIN;
 
 public class CardAdapter extends RecyclerView.Adapter<AbstractCardViewHolder> implements DragAndDropAdapter<FullCard>, CardOptionsItemSelectedListener, Branded {
 
+    private final ExecutorService executor;
     private final boolean compactMode;
     @NonNull
     protected final MainViewModel mainViewModel;
@@ -66,6 +69,10 @@ public class CardAdapter extends RecyclerView.Adapter<AbstractCardViewHolder> im
     protected final int maxCoverImages;
 
     public CardAdapter(@NonNull Activity activity, @NonNull FragmentManager fragmentManager, long stackId, @NonNull MainViewModel mainViewModel, @Nullable SelectCardListener selectCardListener) {
+        this(activity, fragmentManager, stackId, mainViewModel, selectCardListener, Executors.newSingleThreadExecutor());
+    }
+
+    private CardAdapter(@NonNull Activity activity, @NonNull FragmentManager fragmentManager, long stackId, @NonNull MainViewModel mainViewModel, @Nullable SelectCardListener selectCardListener, @NonNull ExecutorService executor) {
         this.activity = activity;
         this.counterMaxValue = this.activity.getString(R.string.counter_max_value);
         this.fragmentManager = fragmentManager;
@@ -79,6 +86,7 @@ public class CardAdapter extends RecyclerView.Adapter<AbstractCardViewHolder> im
                 ? activity.getResources().getInteger(R.integer.max_cover_images)
                 : 0;
         setHasStableIds(true);
+        this.executor = executor;
     }
 
     @Override
@@ -204,10 +212,10 @@ public class CardAdapter extends RecyclerView.Adapter<AbstractCardViewHolder> im
                     .putExtra(Intent.EXTRA_TEXT, CardUtil.getCardContentAsString(activity, fullCard));
             activity.startActivity(Intent.createChooser(shareIntent, fullCard.getCard().getTitle()));
         } else if (itemId == R.id.action_card_assign) {
-            new Thread(() -> mainViewModel.assignUserToCard(mainViewModel.getUserByUidDirectly(fullCard.getCard().getAccountId(), account.getUserName()), fullCard.getCard())).start();
+            executor.submit(() -> mainViewModel.assignUserToCard(mainViewModel.getUserByUidDirectly(fullCard.getCard().getAccountId(), account.getUserName()), fullCard.getCard()));
             return true;
         } else if (itemId == R.id.action_card_unassign) {
-            new Thread(() -> mainViewModel.unassignUserFromCard(mainViewModel.getUserByUidDirectly(fullCard.getCard().getAccountId(), account.getUserName()), fullCard.getCard())).start();
+            executor.submit(() -> mainViewModel.unassignUserFromCard(mainViewModel.getUserByUidDirectly(fullCard.getCard().getAccountId(), account.getUserName()), fullCard.getCard()));
             return true;
         } else if (itemId == R.id.action_card_move) {
             DeckLog.verbose("[Move card] Launch move dialog for " + Card.class.getSimpleName() + " \"" + fullCard.getCard().getTitle() + "\" (#" + fullCard.getLocalId() + ") from " + Stack.class.getSimpleName() + " #" + +stackId);
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/attachments/CardAttachmentsFragment.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/attachments/CardAttachmentsFragment.java
index 4b6d308ae..9dc7020b3 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/attachments/CardAttachmentsFragment.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/attachments/CardAttachmentsFragment.java
@@ -38,6 +38,8 @@ import java.io.IOException;
 import java.time.Instant;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import id.zelory.compressor.constraint.FormatConstraint;
 import id.zelory.compressor.constraint.QualityConstraint;
@@ -95,6 +97,7 @@ public class CardAttachmentsFragment extends Fragment implements AttachmentDelet
     private PreviewDialogViewModel previewViewModel;
     private BottomSheetBehavior<LinearLayout> mBottomSheetBehaviour;
     private boolean compressImagesOnUpload = true;
+    private final ExecutorService executor = Executors.newCachedThreadPool();
 
     private RecyclerView.ItemDecoration galleryItemDecoration;
 
@@ -406,7 +409,7 @@ public class CardAttachmentsFragment extends Fragment implements AttachmentDelet
                 DeckLog.verbose("--- found content URL", sourceUri.getPath());
                 // Separate Thread required because picked file might not yet be locally available
                 // https://github.com/stefan-niedermann/nextcloud-deck/issues/814
-                new Thread(() -> {
+                executor.submit(() -> {
                     try {
                         final File originalFile = copyContentUriToTempFile(requireContext(), sourceUri, editViewModel.getAccount().getId(), editViewModel.getFullCard().getLocalId());
                         requireActivity().runOnUiThread(() -> {
@@ -432,7 +435,7 @@ public class CardAttachmentsFragment extends Fragment implements AttachmentDelet
                     } catch (IOException e) {
                         requireActivity().runOnUiThread(() -> ExceptionDialogFragment.newInstance(e, editViewModel.getAccount()).show(getChildFragmentManager(), ExceptionDialogFragment.class.getSimpleName()));
                     }
-                }).start();
+                });
                 break;
             }
             default: {
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/upcomingcards/UpcomingCardsViewModel.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/upcomingcards/UpcomingCardsViewModel.java
index 23336c91f..8914a87ed 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/upcomingcards/UpcomingCardsViewModel.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/upcomingcards/UpcomingCardsViewModel.java
@@ -7,6 +7,8 @@ import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
 
 import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import it.niedermann.nextcloud.deck.api.IResponseCallback;
 import it.niedermann.nextcloud.deck.model.Account;
@@ -19,10 +21,12 @@ import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.util.WrappedLiv
 public class UpcomingCardsViewModel extends AndroidViewModel {
 
     private final SyncManager syncManager;
+    private final ExecutorService executor;
 
     public UpcomingCardsViewModel(@NonNull Application application) {
         super(application);
         this.syncManager = new SyncManager(application);
+        this.executor = Executors.newCachedThreadPool();
     }
 
     public LiveData<List<UpcomingCardsAdapterItem>> getUpcomingCards() {
@@ -30,11 +34,11 @@ public class UpcomingCardsViewModel extends AndroidViewModel {
     }
 
     public void assignUser(@NonNull Account account, @NonNull Card card) {
-        new Thread(() -> syncManager.assignUserToCard(syncManager.getUserByUidDirectly(card.getAccountId(), account.getUserName()), card)).start();
+        executor.submit(() -> syncManager.assignUserToCard(syncManager.getUserByUidDirectly(card.getAccountId(), account.getUserName()), card));
     }
 
     public void unassignUser(@NonNull Account account, @NonNull Card card) {
-        new Thread(() -> syncManager.unassignUserFromCard(syncManager.getUserByUidDirectly(card.getAccountId(), account.getUserName()), card)).start();
+        executor.submit(() -> syncManager.unassignUserFromCard(syncManager.getUserByUidDirectly(card.getAccountId(), account.getUserName()), card));
     }
 
     public void archiveCard(@NonNull FullCard card, @NonNull IResponseCallback<FullCard> callback) {
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/filter/FilterWidget.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/filter/FilterWidget.java
index 89d75eeee..56ea508c0 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/filter/FilterWidget.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/filter/FilterWidget.java
@@ -7,7 +7,11 @@ import android.content.Context;
 import android.content.Intent;
 import android.os.Bundle;
 
+import androidx.annotation.NonNull;
+
 import java.util.NoSuchElementException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import it.niedermann.nextcloud.deck.DeckLog;
 import it.niedermann.nextcloud.deck.model.Account;
@@ -18,26 +22,26 @@ import static android.appwidget.AppWidgetManager.ACTION_APPWIDGET_UPDATE;
 public class FilterWidget extends AppWidgetProvider {
     public static final String ACCOUNT_KEY = "filter_widget_account";
     public static final String BUNDLE_KEY = "filter_widget_bundle";
+    final ExecutorService executor = Executors.newCachedThreadPool();
 
-    static void updateAppWidget(Context context, AppWidgetManager awm, int[] appWidgetIds, Account account) {
+    static void updateAppWidget(@NonNull ExecutorService executor, @NonNull Context context, AppWidgetManager awm, int[] appWidgetIds, Account account) {
         final SyncManager syncManager = new SyncManager(context);
-
         for (int appWidgetId : appWidgetIds) {
-            new Thread(() -> {
+            executor.submit(() -> {
                 try {
                     // TODO implement
                     throw new UnsupportedOperationException("Not yet implemented");
                 } catch (NoSuchElementException e) {
                     // onUpdate has been triggered before the user finished configuring the widget
                 }
-            }).start();
+            });
         }
     }
 
     @Override
     public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
         super.onUpdate(context, appWidgetManager, appWidgetIds);
-        updateAppWidget(context, appWidgetManager, appWidgetIds, null);
+        updateAppWidget(executor, context, appWidgetManager, appWidgetIds, null);
     }
 
     @Override
@@ -56,10 +60,10 @@ public class FilterWidget extends AppWidgetProvider {
 
                     if (intent.hasExtra(AppWidgetManager.EXTRA_APPWIDGET_ID)) {
                         if (intent.getExtras() != null) {
-                            updateAppWidget(context, awm, new int[]{intent.getExtras().getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, -1)}, account);
+                            updateAppWidget(executor, context, awm, new int[]{intent.getExtras().getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, -1)}, account);
                         }
                     } else {
-                        updateAppWidget(context, awm, awm.getAppWidgetIds(new ComponentName(context, FilterWidget.class)), account);
+                        updateAppWidget(executor, context, awm, awm.getAppWidgetIds(new ComponentName(context, FilterWidget.class)), account);
                     }
                 }
             }
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/singlecard/SingleCardWidget.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/singlecard/SingleCardWidget.java
index 766948062..b3e4d622b 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/singlecard/SingleCardWidget.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/singlecard/SingleCardWidget.java
@@ -15,6 +15,8 @@ import androidx.annotation.IdRes;
 import androidx.annotation.NonNull;
 
 import java.util.NoSuchElementException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import it.niedermann.nextcloud.deck.R;
 import it.niedermann.nextcloud.deck.model.Card;
@@ -25,11 +27,13 @@ import it.niedermann.nextcloud.deck.util.DateUtil;
 
 public class SingleCardWidget extends AppWidgetProvider {
 
+    private final ExecutorService executor = Executors.newCachedThreadPool();
+
     void updateAppWidget(Context context, AppWidgetManager awm, int[] appWidgetIds) {
         final SyncManager syncManager = new SyncManager(context);
 
         for (int appWidgetId : appWidgetIds) {
-            new Thread(() -> {
+            executor.submit(() -> {
                 try {
                     final FullSingleCardWidgetModel fullModel = syncManager.getSingleCardWidgetModelDirectly(appWidgetId);
 
@@ -106,7 +110,7 @@ public class SingleCardWidget extends AppWidgetProvider {
                 } catch (NoSuchElementException e) {
                     // onUpdate has been triggered before the user finished configuring the widget
                 }
-            }).start();
+            });
         }
     }
 
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/stack/StackWidget.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/stack/StackWidget.java
index 5b0907ef3..02d426bbb 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/stack/StackWidget.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/stack/StackWidget.java
@@ -10,6 +10,10 @@ import android.net.Uri;
 import android.widget.RemoteViews;
 
 import androidx.annotation.ColorInt;
+import androidx.annotation.NonNull;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import it.niedermann.nextcloud.deck.DeckLog;
 import it.niedermann.nextcloud.deck.R;
@@ -23,11 +27,12 @@ import static android.appwidget.AppWidgetManager.ACTION_APPWIDGET_UPDATE;
 public class StackWidget extends AppWidgetProvider {
     private static final int PENDING_INTENT_OPEN_APP_RQ = 0;
     private static final int PENDING_INTENT_EDIT_CARD_RQ = 1;
+    private final ExecutorService executor = Executors.newCachedThreadPool();
 
     @Override
     public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
         super.onUpdate(context, appWidgetManager, appWidgetIds);
-        updateAppWidget(context, appWidgetManager, appWidgetIds);
+        updateAppWidget(executor, context, appWidgetManager, appWidgetIds);
     }
 
     @Override
@@ -40,10 +45,10 @@ public class StackWidget extends AppWidgetProvider {
             if (intent.hasExtra(AppWidgetManager.EXTRA_APPWIDGET_ID)) {
                 final int appWidgetId = intent.getExtras().getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, -1);
                 DeckLog.verbose(ACTION_APPWIDGET_UPDATE, "for", StackWidget.class.getSimpleName(), "with id", appWidgetId, "→ perform update.");
-                updateAppWidget(context, awm, new int[]{appWidgetId});
+                updateAppWidget(executor, context, awm, new int[]{appWidgetId});
             } else {
                 DeckLog.verbose(ACTION_APPWIDGET_UPDATE, "→ Triggering update for all widgets of type", StackWidget.class.getSimpleName());
-                updateAppWidget(context, awm, awm.getAppWidgetIds(new ComponentName(context, StackWidget.class)));
+                updateAppWidget(executor, context, awm, awm.getAppWidgetIds(new ComponentName(context, StackWidget.class)));
             }
         }
     }
@@ -59,10 +64,10 @@ public class StackWidget extends AppWidgetProvider {
         }
     }
 
-    private static void updateAppWidget(Context context, AppWidgetManager awm, int[] appWidgetIds) {
+    private static void updateAppWidget(@NonNull ExecutorService executor, @NonNull Context context, AppWidgetManager awm, int[] appWidgetIds) {
         final SyncManager syncManager = new SyncManager(context);
         for (int appWidgetId : appWidgetIds) {
-            new Thread(() -> {
+            executor.submit(() -> {
                 if (syncManager.filterWidgetExists(appWidgetId)) {
                     final RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.widget_stack);
 
@@ -94,7 +99,7 @@ public class StackWidget extends AppWidgetProvider {
                 } else {
                     DeckLog.warn("Does not yet exist");
                 }
-            }).start();
+            });
         }
     }
 }
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/upcoming/UpcomingWidget.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/upcoming/UpcomingWidget.java
index a28f1ef4f..42c7989dd 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/upcoming/UpcomingWidget.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/upcoming/UpcomingWidget.java
@@ -12,6 +12,8 @@ import android.widget.RemoteViews;
 import androidx.annotation.NonNull;
 
 import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.stream.Collectors;
 
 import it.niedermann.nextcloud.deck.BuildConfig;
@@ -35,6 +37,7 @@ public class UpcomingWidget extends AppWidgetProvider {
     private static final String PENDING_INTENT_ACTION_OPEN = "open";
     private static final String PENDING_INTENT_PARAM_LOCAL_CARD_ID = "localCardId";
     private static final String PENDING_INTENT_PARAM_ACCOUNT_ID = "accountId";
+    private final ExecutorService executor = Executors.newCachedThreadPool();
 
     @Override
     public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
@@ -42,10 +45,10 @@ public class UpcomingWidget extends AppWidgetProvider {
         final SyncManager syncManager = new SyncManager(context);
 
         for (int appWidgetId : appWidgetIds) {
-            new Thread(() -> {
+            executor.submit(() -> {
                 if (syncManager.filterWidgetExists(appWidgetId)) {
                     DeckLog.warn(UpcomingWidget.class.getSimpleName(), "with id", appWidgetId, "already exists, perform update instead.");
-                    updateAppWidget(context, appWidgetManager, appWidgetIds);
+                    updateAppWidget(executor, context, appWidgetManager, appWidgetIds);
                 } else {
                     final List<Account> accountsList = syncManager.readAccountsDirectly();
                     final FilterWidget config = new FilterWidget(appWidgetId, EWidgetType.UPCOMING_WIDGET);
@@ -59,7 +62,7 @@ public class UpcomingWidget extends AppWidgetProvider {
                         @Override
                         public void onResponse(Integer response) {
                             DeckLog.verbose("Successfully created", UpcomingWidget.class.getSimpleName(), "with id", appWidgetId);
-                            updateAppWidget(context, appWidgetManager, appWidgetIds);
+                            updateAppWidget(executor, context, appWidgetManager, appWidgetIds);
                         }
 
                         @Override
@@ -70,7 +73,7 @@ public class UpcomingWidget extends AppWidgetProvider {
                         }
                     });
                 }
-            }).start();
+            });
         }
     }
 
@@ -84,17 +87,17 @@ public class UpcomingWidget extends AppWidgetProvider {
             if (intent.hasExtra(AppWidgetManager.EXTRA_APPWIDGET_ID)) {
                 final int appWidgetId = intent.getExtras().getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, -1);
                 DeckLog.verbose(ACTION_APPWIDGET_UPDATE, "for", UpcomingWidget.class.getSimpleName(), "with id", appWidgetId, "→ perform update.");
-                updateAppWidget(context, awm, new int[]{appWidgetId});
+                updateAppWidget(executor, context, awm, new int[]{appWidgetId});
             } else {
                 DeckLog.verbose(ACTION_APPWIDGET_UPDATE, "→ Triggering update for all widgets of type", UpcomingWidget.class.getSimpleName());
-                updateAppWidget(context, awm, awm.getAppWidgetIds(new ComponentName(context, UpcomingWidget.class)));
+                updateAppWidget(executor, context, awm, awm.getAppWidgetIds(new ComponentName(context, UpcomingWidget.class)));
             }
         } else if (PENDING_INTENT_ACTION_EDIT.equals(intent.getAction())) {
             if (intent.hasExtra(PENDING_INTENT_PARAM_ACCOUNT_ID) && intent.hasExtra(PENDING_INTENT_PARAM_LOCAL_CARD_ID)) {
-                new Thread(() -> {
+                executor.submit(() -> {
                     final SyncManager syncManager = new SyncManager(context);
                     context.startActivity(EditActivity.createEditCardIntent(context, syncManager.readAccountDirectly(intent.getLongExtra(PENDING_INTENT_PARAM_ACCOUNT_ID, -1)), syncManager.getBoardLocalIdByLocalCardIdDirectly(intent.getLongExtra(PENDING_INTENT_PARAM_LOCAL_CARD_ID, -1)), intent.getLongExtra(PENDING_INTENT_PARAM_LOCAL_CARD_ID, -1)));
-                }).start();
+                });
             } else {
                 DeckLog.error(PENDING_INTENT_PARAM_ACCOUNT_ID, "and", PENDING_INTENT_PARAM_LOCAL_CARD_ID, "must be provided for action", PENDING_INTENT_ACTION_EDIT);
             }
@@ -114,9 +117,9 @@ public class UpcomingWidget extends AppWidgetProvider {
         }
     }
 
-    private static void updateAppWidget(@NonNull Context context, @NonNull AppWidgetManager awm, int[] appWidgetIds) {
+    private static void updateAppWidget(@NonNull ExecutorService executor, @NonNull Context context, @NonNull AppWidgetManager awm, int[] appWidgetIds) {
         for (int appWidgetId : appWidgetIds) {
-            new Thread(() -> {
+            executor.submit(() -> {
                 final RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.widget_upcoming);
 
                 final Intent serviceIntent = new Intent(context, UpcomingWidgetService.class);
@@ -131,7 +134,7 @@ public class UpcomingWidget extends AppWidgetProvider {
 
                 awm.notifyAppWidgetViewDataChanged(appWidgetId, R.id.upcoming_widget_lv);
                 awm.updateAppWidget(appWidgetId, views);
-            }).start();
+            });
         }
     }