Merge branch 'master' into 454-replay-to-comments

# Conflicts:
#	app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/DataBaseAdapter.java
#	app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/DeckDatabase.java

19 files changed, 550 insertions, 44 deletions

diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/api/JsonToEntityParser.java b/app/src/main/java/it/niedermann/nextcloud/deck/api/JsonToEntityParser.java
index 4a31ad54f..1b6d517a6 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/api/JsonToEntityParser.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/api/JsonToEntityParser.java
@@ -344,7 +344,9 @@ public class JsonToEntityParser {
                         JsonObject deck = caps.getAsJsonObject("deck");
                         if (deck.has("version")) {
                             version = deck.get("version").getAsString();
-
+                            if (version == null || version.trim().length() < 1) {
+                                throw new IllegalArgumentException("capabilities endpoint returned an invalid version string: \""+version+"\"");
+                            }
                         }
                     }
                     if (caps.has("theming")) {
@@ -353,6 +355,9 @@ public class JsonToEntityParser {
                         capabilities.setTextColor(theming.get("color-text").getAsString());
                     }
                 }
+                if (version == null || version.trim().length() < 1) {
+                    throw new IllegalArgumentException("capabilities endpoint returned no version string at all!");
+                }
                 capabilities.setDeckVersion(Version.of(version));
             }
         }
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/model/full/FullSingleCardWidgetModel.java b/app/src/main/java/it/niedermann/nextcloud/deck/model/full/FullSingleCardWidgetModel.java
new file mode 100644
index 000000000..c9786f4d2
--- /dev/null
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/model/full/FullSingleCardWidgetModel.java
@@ -0,0 +1,44 @@
+package it.niedermann.nextcloud.deck.model.full;
+
+import androidx.room.Embedded;
+import androidx.room.Ignore;
+import androidx.room.Relation;
+
+import it.niedermann.nextcloud.deck.model.Account;
+import it.niedermann.nextcloud.deck.model.widget.singlecard.SingleCardWidgetModel;
+
+public class FullSingleCardWidgetModel {
+
+    @Embedded
+    private SingleCardWidgetModel model;
+
+    @Relation(parentColumn = "accountId", entityColumn = "id")
+    private Account account;
+
+    @Ignore
+    private FullCard fullCard;
+
+    public SingleCardWidgetModel getModel() {
+        return model;
+    }
+
+    public void setModel(SingleCardWidgetModel model) {
+        this.model = model;
+    }
+
+    public Account getAccount() {
+        return account;
+    }
+
+    public void setAccount(Account account) {
+        this.account = account;
+    }
+
+    public FullCard getFullCard() {
+        return fullCard;
+    }
+
+    public void setFullCard(FullCard fullCard) {
+        this.fullCard = fullCard;
+    }
+}
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/model/ocs/Version.java b/app/src/main/java/it/niedermann/nextcloud/deck/model/ocs/Version.java
index 5e7169472..701cdd335 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/model/ocs/Version.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/model/ocs/Version.java
@@ -80,7 +80,7 @@ public class Version implements Comparable<Version> {
         if (matcher.find()) {
             return Integer.parseInt(matcher.group());
         }
-        return 0;
+        throw new IllegalArgumentException("could not extract a number from following string: \""+containsNumbers+"\"");
     }
 
     @NonNull
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/model/widget/singlecard/SingleCardWidgetModel.java b/app/src/main/java/it/niedermann/nextcloud/deck/model/widget/singlecard/SingleCardWidgetModel.java
new file mode 100644
index 000000000..fcaab380b
--- /dev/null
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/model/widget/singlecard/SingleCardWidgetModel.java
@@ -0,0 +1,86 @@
+package it.niedermann.nextcloud.deck.model.widget.singlecard;
+
+import androidx.room.Entity;
+import androidx.room.ForeignKey;
+import androidx.room.Ignore;
+import androidx.room.Index;
+import androidx.room.PrimaryKey;
+
+import it.niedermann.nextcloud.deck.model.Account;
+import it.niedermann.nextcloud.deck.model.Board;
+import it.niedermann.nextcloud.deck.model.Card;
+
+@Entity(
+        indices = {
+                @Index("cardId")
+        },
+        foreignKeys = {
+                @ForeignKey(
+                        entity = Account.class,
+                        parentColumns = "id",
+                        childColumns = "accountId", onDelete = ForeignKey.CASCADE
+                ),
+                @ForeignKey(
+                        entity = Board.class,
+                        parentColumns = "localId",
+                        childColumns = "boardId", onDelete = ForeignKey.CASCADE
+                ),
+                @ForeignKey(
+                        entity = Card.class,
+                        parentColumns = "localId",
+                        childColumns = "cardId", onDelete = ForeignKey.CASCADE
+                )
+        }
+)
+public class SingleCardWidgetModel {
+    @Ignore
+    private static final long serialVersionUID = 0;
+
+    @PrimaryKey()
+    private Integer widgetId;
+    private Long accountId;
+    private Long boardId;
+    private Long cardId;
+
+    public Integer getWidgetId() {
+        return widgetId;
+    }
+
+    public void setWidgetId(Integer widgetId) {
+        this.widgetId = widgetId;
+    }
+
+    public Long getAccountId() {
+        return accountId;
+    }
+
+    public void setAccountId(Long accountId) {
+        this.accountId = accountId;
+    }
+
+    public Long getBoardId() {
+        return boardId;
+    }
+
+    public void setBoardId(Long boardId) {
+        this.boardId = boardId;
+    }
+
+    public Long getCardId() {
+        return cardId;
+    }
+
+    public void setCardId(Long cardId) {
+        this.cardId = cardId;
+    }
+
+    @Override
+    public String toString() {
+        return "SingleCardWidget{" +
+                "widgetId=" + widgetId +
+                ", accountId=" + accountId +
+                ", boardId=" + boardId +
+                ", cardId=" + cardId +
+                '}';
+    }
+}
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/SyncManager.java b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/SyncManager.java
index 5722f0f1e..29f7725b8 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/SyncManager.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/SyncManager.java
@@ -5,6 +5,7 @@ import android.database.sqlite.SQLiteConstraintException;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.annotation.WorkerThread;
 import androidx.core.util.Pair;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
@@ -16,6 +17,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Date;
 import java.util.List;
+import java.util.NoSuchElementException;
 import java.util.concurrent.CountDownLatch;
 
 import it.niedermann.nextcloud.deck.DeckLog;
@@ -35,6 +37,7 @@ import it.niedermann.nextcloud.deck.model.User;
 import it.niedermann.nextcloud.deck.model.enums.DBStatus;
 import it.niedermann.nextcloud.deck.model.full.FullBoard;
 import it.niedermann.nextcloud.deck.model.full.FullCard;
+import it.niedermann.nextcloud.deck.model.full.FullSingleCardWidgetModel;
 import it.niedermann.nextcloud.deck.model.full.FullStack;
 import it.niedermann.nextcloud.deck.model.internal.FilterInformation;
 import it.niedermann.nextcloud.deck.model.ocs.Capabilities;
@@ -1281,6 +1284,30 @@ public class SyncManager {
         return liveData;
     }
 
+    // -------------------
+    // Widgets
+    // -------------------
+
+    /**
+     * Can be called from a configuration screen or a picker.
+     * Creates a new entry in the database, if row with given widgetId does not yet exist.
+     */
+    public void addOrUpdateSingleCardWidget(int widgetId, long accountId, long boardId, long localCardId) {
+        doAsync(() -> dataBaseAdapter.createSingleCardWidget(widgetId, accountId, boardId, localCardId));
+    }
+
+    @WorkerThread
+    public FullSingleCardWidgetModel getSingleCardWidgetModelDirectly(int widgetId) throws NoSuchElementException {
+        final FullSingleCardWidgetModel model = dataBaseAdapter.getFullSingleCardWidgetModel(widgetId);
+        if (model == null) {
+            throw new NoSuchElementException();
+        }
+        return model;
+    }
+
+    public void deleteSingleCardWidgetModel(int widgetId) {
+        doAsync(() -> dataBaseAdapter.deleteSingleCardWidget(widgetId));
+    }
 
     private static class BooleanResultHolder {
         public boolean result = true;
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/DataBaseAdapter.java b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/DataBaseAdapter.java
index 821d910ab..37d2660e5 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/DataBaseAdapter.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/DataBaseAdapter.java
@@ -12,6 +12,7 @@ import java.util.ArrayList;
 import java.util.Date;
 import java.util.List;
 
+import it.niedermann.nextcloud.deck.DeckLog;
 import it.niedermann.nextcloud.deck.model.AccessControl;
 import it.niedermann.nextcloud.deck.model.Account;
 import it.niedermann.nextcloud.deck.model.Attachment;
@@ -27,6 +28,7 @@ import it.niedermann.nextcloud.deck.model.enums.DBStatus;
 import it.niedermann.nextcloud.deck.model.enums.EDueType;
 import it.niedermann.nextcloud.deck.model.full.FullBoard;
 import it.niedermann.nextcloud.deck.model.full.FullCard;
+import it.niedermann.nextcloud.deck.model.full.FullSingleCardWidgetModel;
 import it.niedermann.nextcloud.deck.model.full.FullStack;
 import it.niedermann.nextcloud.deck.model.interfaces.AbstractRemoteEntity;
 import it.niedermann.nextcloud.deck.model.interfaces.IRemoteEntity;
@@ -34,9 +36,11 @@ import it.niedermann.nextcloud.deck.model.internal.FilterInformation;
 import it.niedermann.nextcloud.deck.model.ocs.Activity;
 import it.niedermann.nextcloud.deck.model.ocs.comment.DeckComment;
 import it.niedermann.nextcloud.deck.model.ocs.comment.Mention;
+import it.niedermann.nextcloud.deck.model.widget.singlecard.SingleCardWidgetModel;
 import it.niedermann.nextcloud.deck.model.ocs.comment.full.FullDeckComment;
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.util.LiveDataHelper;
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.util.WrappedLiveData;
+import it.niedermann.nextcloud.deck.ui.widget.singlecard.SingleCardWidget;
 
 import static androidx.lifecycle.Transformations.distinctUntilChanged;
 
@@ -174,7 +178,7 @@ public class DataBaseAdapter {
             return LiveDataHelper.interceptLiveData(db.getCardDao().getFullCardsForStack(accountId, localStackId), this::filterRelationsForCard);
         }
 
-        List<Object> args = new ArrayList();
+        List<Object> args = new ArrayList<>();
         StringBuilder query = new StringBuilder("SELECT * FROM card c " +
                 "WHERE accountId = ? AND stackId = ? ");
         args.add(accountId);
@@ -488,6 +492,10 @@ public class DataBaseAdapter {
     public void updateCard(Card card, boolean setStatus) {
         markAsEditedIfNeeded(card, setStatus);
         db.getCardDao().update(card);
+        if (db.getSingleCardWidgetModelDao().containsCardLocalId(card.getLocalId())) {
+            DeckLog.info("Notifying widget about card changes for \"" + card.getTitle() + "\"");
+            SingleCardWidget.notifyDatasetChanged(context);
+        }
     }
 
     public long createAccessControl(long accountId, AccessControl entity) {
@@ -829,4 +837,32 @@ public class DataBaseAdapter {
     public Long getLocalCommentIdForRemoteIdDirectly(long accountId, Long remoteCommentId) {
         return db.getCommentDao().getLocalCommentIdForRemoteIdDirectly(accountId, remoteCommentId);
     }
+
+
+    // -------------------
+    // Widgets
+    // -------------------
+
+    public long createSingleCardWidget(int widgetId, long accountId, long boardLocalId, long cardLocalId) {
+        SingleCardWidgetModel model = new SingleCardWidgetModel();
+        model.setWidgetId(widgetId);
+        model.setAccountId(accountId);
+        model.setBoardId(boardLocalId);
+        model.setCardId(cardLocalId);
+        return db.getSingleCardWidgetModelDao().insert(model);
+    }
+
+    public FullSingleCardWidgetModel getFullSingleCardWidgetModel(int widgetId) {
+        FullSingleCardWidgetModel model = db.getSingleCardWidgetModelDao().getFullCardByRemoteIdDirectly(widgetId);
+        if (model != null) {
+            model.setFullCard(db.getCardDao().getFullCardByLocalIdDirectly(model.getAccount().getId(), model.getModel().getCardId()));
+        }
+        return model;
+    }
+
+    public void deleteSingleCardWidget(int widgetId) {
+        SingleCardWidgetModel model = new SingleCardWidgetModel();
+        model.setWidgetId(widgetId);
+        db.getSingleCardWidgetModelDao().delete(model);
+    }
 }
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/DeckDatabase.java b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/DeckDatabase.java
index 3e2b6dec4..a87a60cd2 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/DeckDatabase.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/DeckDatabase.java
@@ -31,6 +31,7 @@ import it.niedermann.nextcloud.deck.model.enums.DBStatus;
 import it.niedermann.nextcloud.deck.model.ocs.Activity;
 import it.niedermann.nextcloud.deck.model.ocs.comment.DeckComment;
 import it.niedermann.nextcloud.deck.model.ocs.comment.Mention;
+import it.niedermann.nextcloud.deck.model.widget.singlecard.SingleCardWidgetModel;
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.AccessControlDao;
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.AccountDao;
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.ActivityDao;
@@ -46,6 +47,7 @@ import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.JoinCardWit
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.LabelDao;
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.MentionDao;
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.PermissionDao;
+import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.SingleCardWidgetModelDao;
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.StackDao;
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.UserDao;
 
@@ -68,6 +70,7 @@ import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao.UserDao;
                 Activity.class,
                 DeckComment.class,
                 Mention.class,
+                SingleCardWidgetModel.class,
         },
         exportSchema = false,
         version = 12
@@ -149,6 +152,14 @@ public abstract class DeckDatabase extends RoomDatabase {
     private static final Migration MIGRATION_11_12 = new Migration(11, 12) {
         @Override
         public void migrate(SupportSQLiteDatabase database) {
+            database.execSQL("CREATE TABLE `SingleCardWidgetModel` (`widgetId` INTEGER PRIMARY KEY, `accountId` INTEGER, `boardId` INTEGER, `cardId` INTEGER, FOREIGN KEY(`accountId`) REFERENCES `Account`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE, FOREIGN KEY(`boardId`) REFERENCES `Board`(`localId`) ON UPDATE NO ACTION ON DELETE CASCADE, FOREIGN KEY(`cardId`) REFERENCES `Card`(`localId`) ON UPDATE NO ACTION ON DELETE CASCADE )");
+            database.execSQL("CREATE INDEX `index_SingleCardWidgetModel_cardId` ON `SingleCardWidgetModel` (`cardId`)");
+        }
+    };
+
+    private static final Migration MIGRATION_12_13 = new Migration(11, 12) {
+        @Override
+        public void migrate(SupportSQLiteDatabase database) {
             database.execSQL("ALTER TABLE `DeckComment` ADD `parentId` INTEGER REFERENCES DeckComment(localId) ON DELETE CASCADE");
             database.execSQL("CREATE INDEX `idx_comment_parentID` ON DeckComment(parentId)");
         }
@@ -180,12 +191,14 @@ public abstract class DeckDatabase extends RoomDatabase {
                 .addMigrations(MIGRATION_9_10)
                 .addMigrations(MIGRATION_10_11)
                 .addMigrations(MIGRATION_11_12)
+                .addMigrations(MIGRATION_12_13)
                 .fallbackToDestructiveMigration()
                 .addCallback(ON_CREATE_CALLBACK)
                 .build();
     }
 
     public abstract AccountDao getAccountDao();
+
     public abstract AccessControlDao getAccessControlDao();
 
     public abstract BoardDao getBoardDao();
@@ -217,4 +230,6 @@ public abstract class DeckDatabase extends RoomDatabase {
     public abstract CommentDao getCommentDao();
 
     public abstract MentionDao getMentionDao();
+
+    public abstract SingleCardWidgetModelDao getSingleCardWidgetModelDao();
 }
\ No newline at end of file
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/dao/CardDao.java b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/dao/CardDao.java
index e58f2c819..d63f98b6a 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/dao/CardDao.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/dao/CardDao.java
@@ -33,7 +33,7 @@ public interface CardDao extends GenericDao<Card> {
     FullCard getFullCardByLocalIdDirectly(final long accountId, final long localId);
 
     @Transaction                                                                                // v not deleted!
-    @Query("SELECT * FROM card WHERE accountId = :accountId AND stackId = :localStackId and status<>3 order by `order`, createdAt asc")
+    @Query("SELECT * FROM card WHERE accountId = :accountId AND archived = 0 AND stackId = :localStackId and status<>3 order by `order`, createdAt asc")
     LiveData<List<FullCard>> getFullCardsForStack(final long accountId, final long localStackId);
 
     @Transaction                                                                                // v not deleted!
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/dao/SingleCardWidgetModelDao.java b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/dao/SingleCardWidgetModelDao.java
new file mode 100644
index 000000000..0c2a485c1
--- /dev/null
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/dao/SingleCardWidgetModelDao.java
@@ -0,0 +1,20 @@
+package it.niedermann.nextcloud.deck.persistence.sync.adapters.db.dao;
+
+import androidx.room.Dao;
+import androidx.room.Query;
+import androidx.room.Transaction;
+
+import it.niedermann.nextcloud.deck.model.full.FullSingleCardWidgetModel;
+import it.niedermann.nextcloud.deck.model.widget.singlecard.SingleCardWidgetModel;
+
+@Dao
+public interface SingleCardWidgetModelDao extends GenericDao<SingleCardWidgetModel> {
+
+    @Transaction
+    @Query("SELECT * FROM singlecardwidgetmodel WHERE widgetId = :widgetId")
+    FullSingleCardWidgetModel getFullCardByRemoteIdDirectly(final int widgetId);
+
+    @Transaction
+    @Query("SELECT EXISTS (SELECT 1 FROM singlecardwidgetmodel WHERE cardId = :cardLocalId)")
+    boolean containsCardLocalId(final Long cardLocalId);
+}
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/MainActivity.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/MainActivity.java
index f4d744f11..6d2623a91 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/MainActivity.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/MainActivity.java
@@ -364,8 +364,12 @@ public class MainActivity extends BrandedActivity implements DeleteStackListener
     protected void onStop() {
         // Clean up zombie fragments in case of system initiated process death.
         // See linked issues in https://github.com/stefan-niedermann/nextcloud-deck/issues/478
-        for (Fragment fragment : getSupportFragmentManager().getFragments()) {
-            getSupportFragmentManager().beginTransaction().remove(fragment).commit();
+        try {
+            for (Fragment fragment : getSupportFragmentManager().getFragments()) {
+                getSupportFragmentManager().beginTransaction().remove(fragment).commit();
+            }
+        } catch (IllegalStateException e) {
+            DeckLog.warn("onSAveInstanceState has already been called.");
         }
         super.onStop();
     }
@@ -411,8 +415,12 @@ public class MainActivity extends BrandedActivity implements DeleteStackListener
     public void onUpdateStack(long localStackId, String stackName) {
         observeOnce(syncManager.getStack(mainViewModel.getCurrentAccount().getId(), localStackId), MainActivity.this, fullStack -> {
             fullStack.getStack().setTitle(stackName);
-            // TODO error handling
-            syncManager.updateStack(fullStack);
+            final WrappedLiveData<FullStack> archiveLiveData = syncManager.updateStack(fullStack);
+            observeOnce(archiveLiveData, this, (v) -> {
+                if (archiveLiveData.hasError()) {
+                    ExceptionDialogFragment.newInstance(archiveLiveData.getError(), mainViewModel.getCurrentAccount()).show(getSupportFragmentManager(), ExceptionDialogFragment.class.getSimpleName());
+                }
+            });
         });
     }
 
@@ -974,9 +982,13 @@ public class MainActivity extends BrandedActivity implements DeleteStackListener
     public void onStackDeleted(Long stackLocalId) {
         long stackId = stackAdapter.getItem(binding.viewPager.getCurrentItem()).getLocalId();
         observeOnce(syncManager.getStack(mainViewModel.getCurrentAccount().getId(), stackId), MainActivity.this, fullStack -> {
-            DeckLog.log("Delete stack #" + fullStack.getLocalId() + ": " + fullStack.getStack().getTitle());
-            // TODO error handling
-            syncManager.deleteStack(fullStack.getStack());
+            DeckLog.info("Delete stack #" + fullStack.getLocalId() + ": " + fullStack.getStack().getTitle());
+            final WrappedLiveData<Void> deleteStackLiveData = syncManager.deleteStack(fullStack.getStack());
+            observeOnce(deleteStackLiveData, this, (v) -> {
+                if (deleteStackLiveData.hasError()) {
+                    ExceptionDialogFragment.newInstance(deleteStackLiveData.getError(), mainViewModel.getCurrentAccount()).show(getSupportFragmentManager(), ExceptionDialogFragment.class.getSimpleName());
+                }
+            });
         });
     }
 
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/archivedcards/ArchivedCardsActvitiy.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/archivedcards/ArchivedCardsActvitiy.java
index e8dd9b8dd..00500ae97 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/archivedcards/ArchivedCardsActvitiy.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/archivedcards/ArchivedCardsActvitiy.java
@@ -55,7 +55,7 @@ public class ArchivedCardsActvitiy extends BrandedActivity {
 
         syncManager = new SyncManager(this);
 
-        adapter = new ArchivedCardsAdapter(this, account, boardId, false, syncManager, this);
+        adapter = new ArchivedCardsAdapter(this, getSupportFragmentManager(), account, boardId, false, syncManager, this);
         binding.recyclerView.setAdapter(adapter);
 
         syncManager.getArchivedFullCardsForBoard(account.getId(), boardId).observe(this, (fullCards) -> {
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/archivedcards/ArchivedCardsAdapter.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/archivedcards/ArchivedCardsAdapter.java
index 955749dd0..80502ef38 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/archivedcards/ArchivedCardsAdapter.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/archivedcards/ArchivedCardsAdapter.java
@@ -7,6 +7,7 @@ import android.view.View;
 import android.widget.PopupMenu;
 
 import androidx.annotation.NonNull;
+import androidx.fragment.app.FragmentManager;
 import androidx.lifecycle.LifecycleOwner;
 
 import org.jetbrains.annotations.NotNull;
@@ -21,8 +22,8 @@ import it.niedermann.nextcloud.deck.ui.card.ItemCardViewHolder;
 public class ArchivedCardsAdapter extends CardAdapter {
 
     @SuppressWarnings("WeakerAccess")
-    public ArchivedCardsAdapter(@NonNull Context context, @NonNull Account account, long boardId, boolean canEdit, @NonNull SyncManager syncManager, @NonNull LifecycleOwner lifecycleOwner) {
-        super(context, account, boardId, 0L, canEdit, syncManager, lifecycleOwner, null);
+    public ArchivedCardsAdapter(@NonNull Context context, @NonNull FragmentManager fragmentManager, @NonNull Account account, long boardId, boolean canEdit, @NonNull SyncManager syncManager, @NonNull LifecycleOwner lifecycleOwner) {
+        super(context, fragmentManager, account, boardId, 0L, canEdit, syncManager, lifecycleOwner, null);
     }
 
     @Override
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 f9b8a46de..15902bd14 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
@@ -14,6 +14,7 @@ import android.widget.TextView;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.core.graphics.drawable.DrawableCompat;
+import androidx.fragment.app.FragmentManager;
 import androidx.lifecycle.LifecycleOwner;
 import androidx.recyclerview.widget.RecyclerView;
 
@@ -39,16 +40,21 @@ import it.niedermann.nextcloud.deck.model.full.FullCard;
 import it.niedermann.nextcloud.deck.model.full.FullStack;
 import it.niedermann.nextcloud.deck.persistence.sync.SyncManager;
 import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.util.LiveDataHelper;
+import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.util.WrappedLiveData;
 import it.niedermann.nextcloud.deck.ui.branding.Branded;
 import it.niedermann.nextcloud.deck.ui.branding.BrandedActivity;
 import it.niedermann.nextcloud.deck.ui.branding.BrandedAlertDialogBuilder;
+import it.niedermann.nextcloud.deck.ui.exception.ExceptionDialogFragment;
 import it.niedermann.nextcloud.deck.util.DateUtil;
 import it.niedermann.nextcloud.deck.util.ViewUtil;
 
+import static it.niedermann.nextcloud.deck.persistence.sync.adapters.db.util.LiveDataHelper.observeOnce;
+
 public class CardAdapter extends RecyclerView.Adapter<ItemCardViewHolder> implements DragAndDropAdapter<FullCard>, Branded {
 
     protected final SyncManager syncManager;
 
+    private final FragmentManager fragmentManager;
     private final Account account;
     private final long boardId;
     private final long stackId;
@@ -64,8 +70,9 @@ public class CardAdapter extends RecyclerView.Adapter<ItemCardViewHolder> implem
 
     private int mainColor;
 
-    public CardAdapter(@NonNull Context context, @NonNull Account account, long boardId, long stackId, boolean canEdit, @NonNull SyncManager syncManager, @NonNull LifecycleOwner lifecycleOwner, @Nullable SelectCardListener selectCardListener) {
+    public CardAdapter(@NonNull Context context, @NonNull FragmentManager fragmentManager, @NonNull Account account, long boardId, long stackId, boolean canEdit, @NonNull SyncManager syncManager, @NonNull LifecycleOwner lifecycleOwner, @Nullable SelectCardListener selectCardListener) {
         this.context = context;
+        this.fragmentManager = fragmentManager;
         this.lifecycleOwner = lifecycleOwner;
         this.account = account;
         this.boardId = boardId;
@@ -296,13 +303,21 @@ public class CardAdapter extends RecyclerView.Adapter<ItemCardViewHolder> implem
                 return true;
             }
             case R.id.action_card_archive: {
-                // TODO error handling
-                syncManager.archiveCard(fullCard);
+                final WrappedLiveData<FullCard> archiveLiveData = syncManager.archiveCard(fullCard);
+                observeOnce(archiveLiveData, lifecycleOwner, (v) -> {
+                    if (archiveLiveData.hasError()) {
+                        ExceptionDialogFragment.newInstance(archiveLiveData.getError(), account).show(fragmentManager, ExceptionDialogFragment.class.getSimpleName());
+                    }
+                });
                 return true;
             }
             case R.id.action_card_delete: {
-                // TODO error handling
-                syncManager.deleteCard(fullCard.getCard());
+                final WrappedLiveData<Void> deleteLiveData = syncManager.deleteCard(fullCard.getCard());
+                observeOnce(deleteLiveData, lifecycleOwner, (v) -> {
+                    if (deleteLiveData.hasError()) {
+                        ExceptionDialogFragment.newInstance(deleteLiveData.getError(), account).show(fragmentManager, ExceptionDialogFragment.class.getSimpleName());
+                    }
+                });
                 return true;
             }
         }
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/EditActivity.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/EditActivity.java
index f800ae546..8cb13a865 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/EditActivity.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/EditActivity.java
@@ -20,6 +20,7 @@ import androidx.lifecycle.ViewModelProvider;
 import com.google.android.material.tabs.TabLayout;
 import com.google.android.material.tabs.TabLayoutMediator;
 
+import it.niedermann.nextcloud.deck.DeckLog;
 import it.niedermann.nextcloud.deck.R;
 import it.niedermann.nextcloud.deck.databinding.ActivityEditBinding;
 import it.niedermann.nextcloud.deck.model.Account;
@@ -29,6 +30,7 @@ import it.niedermann.nextcloud.deck.ui.branding.BrandedAlertDialogBuilder;
 import it.niedermann.nextcloud.deck.ui.exception.ExceptionHandler;
 import it.niedermann.nextcloud.deck.util.CardUtil;
 
+import static android.graphics.Color.parseColor;
 import static it.niedermann.nextcloud.deck.persistence.sync.adapters.db.util.LiveDataHelper.observeOnce;
 
 public class EditActivity extends BrandedActivity {
@@ -72,14 +74,26 @@ public class EditActivity extends BrandedActivity {
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-
         Thread.currentThread().setUncaughtExceptionHandler(new ExceptionHandler(this));
-
         binding = ActivityEditBinding.inflate(getLayoutInflater());
         setContentView(binding.getRoot());
-
         setSupportActionBar(binding.toolbar);
 
+        viewModel = new ViewModelProvider(this).get(EditCardViewModel.class);
+        syncManager = new SyncManager(this);
+
+        loadDataFromIntent();
+    }
+
+    @Override
+    protected void onNewIntent(Intent intent) {
+        super.onNewIntent(intent);
+        setIntent(intent);
+        loadDataFromIntent();
+        applyBrand(parseColor(viewModel.getAccount().getColor()), parseColor(viewModel.getAccount().getTextColor()));
+    }
+
+    private void loadDataFromIntent() {
         final Bundle args = getIntent().getExtras();
 
         if (args == null || !args.containsKey(BUNDLE_KEY_ACCOUNT) || !args.containsKey(BUNDLE_KEY_BOARD_ID)) {
@@ -88,9 +102,6 @@ public class EditActivity extends BrandedActivity {
 
         long cardId = args.getLong(BUNDLE_KEY_CARD_ID);
 
-        viewModel = new ViewModelProvider(this).get(EditCardViewModel.class);
-        syncManager = new SyncManager(this);
-
         if (cardId == 0L) {
             viewModel.setCreateMode(true);
             if (!args.containsKey(BUNDLE_KEY_STACK_ID)) {
@@ -102,13 +113,16 @@ public class EditActivity extends BrandedActivity {
         if (account == null) {
             throw new IllegalArgumentException(BUNDLE_KEY_ACCOUNT + " must not be null.");
         }
+        viewModel.setAccount(account);
+
         final long boardId = args.getLong(BUNDLE_KEY_BOARD_ID);
 
         observeOnce(syncManager.getFullBoardById(account.getId(), boardId), EditActivity.this, (fullBoard -> {
             viewModel.setCanEdit(fullBoard.getBoard().isPermissionEdit());
             invalidateOptionsMenu();
             if (viewModel.isCreateMode()) {
-                viewModel.initializeNewCard(account, boardId, args.getLong(BUNDLE_KEY_STACK_ID), account.getServerDeckVersionAsObject().isSupported(this));
+                viewModel.initializeNewCard(boardId, args.getLong(BUNDLE_KEY_STACK_ID), account.getServerDeckVersionAsObject().isSupported(this));
+                invalidateOptionsMenu();
                 String title = args.getString(BUNDLE_KEY_TITLE);
                 if (!TextUtils.isEmpty(title)) {
                     if (title.length() > viewModel.getAccount().getServerDeckVersionAsObject().getCardTitleMaxLength()) {
@@ -121,9 +135,18 @@ public class EditActivity extends BrandedActivity {
                 setupTitle();
             } else {
                 observeOnce(syncManager.getCardByLocalId(account.getId(), cardId), EditActivity.this, (fullCard) -> {
-                    viewModel.initializeExistingCard(account, boardId, fullCard, account.getServerDeckVersionAsObject().isSupported(this));
-                    setupViewPager();
-                    setupTitle();
+                    if (fullCard == null) {
+                        new BrandedAlertDialogBuilder(this)
+                                .setTitle(R.string.card_not_found)
+                                .setMessage(R.string.card_not_found_message)
+                                .setPositiveButton(R.string.simple_close, (a, b) -> super.finish())
+                                .show();
+                    } else {
+                        viewModel.initializeExistingCard(boardId, fullCard, account.getServerDeckVersionAsObject().isSupported(this));
+                        invalidateOptionsMenu();
+                        setupViewPager();
+                        setupTitle();
+                    }
                 });
             }
         }));
@@ -264,8 +287,12 @@ public class EditActivity extends BrandedActivity {
     protected void onStop() {
         // Clean up zombie fragments in case of system initiated process death.
         // See linked issues in https://github.com/stefan-niedermann/nextcloud-deck/issues/478
-        for (Fragment fragment : getSupportFragmentManager().getFragments()) {
-            getSupportFragmentManager().beginTransaction().remove(fragment).commit();
+        try {
+            for (Fragment fragment : getSupportFragmentManager().getFragments()) {
+                getSupportFragmentManager().beginTransaction().remove(fragment).commit();
+            }
+        } catch (IllegalStateException e) {
+            DeckLog.warn("onSAveInstanceState has already been called.");
         }
         super.onStop();
     }
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/EditCardViewModel.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/EditCardViewModel.java
index 66ec0d5d8..490c1d57d 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/EditCardViewModel.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/card/EditCardViewModel.java
@@ -25,27 +25,23 @@ public class EditCardViewModel extends ViewModel {
     /**
      * Stores a deep copy of the given fullCard to be able to compare the state at every time in #{@link EditCardViewModel#hasChanges()}
      *
-     * @param account  Must not be null
      * @param boardId  Local ID, expecting a positive long value
      * @param fullCard The card that is currently edited
      */
-    public void initializeExistingCard(@NonNull Account account, long boardId, @NonNull FullCard fullCard, boolean isSupportedVersion) {
-        this.account = account;
+    public void initializeExistingCard(long boardId, @NonNull FullCard fullCard, boolean isSupportedVersion) {
         this.boardId = boardId;
         this.fullCard = fullCard;
         this.originalCard = new FullCard(this.fullCard);
         this.isSupportedVersion = isSupportedVersion;
-        hasCommentsAbility = account.getServerDeckVersionAsObject().supportsComments();
     }
 
     /**
      * Stores a deep copy of the given fullCard to be able to compare the state at every time in #{@link EditCardViewModel#hasChanges()}
      *
-     * @param account Must not be null
      * @param boardId Local ID, expecting a positive long value
      * @param stackId Local ID, expecting a positive long value where the card should be created
      */
-    public void initializeNewCard(@NonNull Account account, long boardId, long stackId, boolean isSupportedVersion) {
+    public void initializeNewCard(long boardId, long stackId, boolean isSupportedVersion) {
         final FullCard fullCard = new FullCard();
         fullCard.setLabels(new ArrayList<>());
         fullCard.setAssignedUsers(new ArrayList<>());
@@ -53,7 +49,12 @@ public class EditCardViewModel extends ViewModel {
         final Card card = new Card();
         card.setStackId(stackId);
         fullCard.setCard(card);
-        initializeExistingCard(account, boardId, fullCard, isSupportedVersion);
+        initializeExistingCard(boardId, fullCard, isSupportedVersion);
+    }
+
+    public void setAccount(@NonNull Account account) {
+        this.account = account;
+        hasCommentsAbility = account.getServerDeckVersionAsObject().supportsComments();
     }
 
     public boolean hasChanges() {
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/preparecreate/PrepareCreateActivity.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/preparecreate/PrepareCreateActivity.java
index 65a0d726d..b2e9cb012 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/preparecreate/PrepareCreateActivity.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/preparecreate/PrepareCreateActivity.java
@@ -5,7 +5,6 @@ import android.content.Intent;
 import android.os.Bundle;
 import android.text.TextUtils;
 import android.widget.ArrayAdapter;
-import android.widget.Toast;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
@@ -16,7 +15,6 @@ import java.util.List;
 
 import it.niedermann.nextcloud.deck.Application;
 import it.niedermann.nextcloud.deck.DeckLog;
-import it.niedermann.nextcloud.deck.R;
 import it.niedermann.nextcloud.deck.databinding.ActivityPrepareCreateBinding;
 import it.niedermann.nextcloud.deck.model.Account;
 import it.niedermann.nextcloud.deck.model.Board;
@@ -25,6 +23,7 @@ import it.niedermann.nextcloud.deck.persistence.sync.SyncManager;
 import it.niedermann.nextcloud.deck.ui.ImportAccountActivity;
 import it.niedermann.nextcloud.deck.ui.branding.BrandedActivity;
 import it.niedermann.nextcloud.deck.ui.card.EditActivity;
+import it.niedermann.nextcloud.deck.ui.exception.ExceptionDialogFragment;
 import it.niedermann.nextcloud.deck.ui.exception.ExceptionHandler;
 
 import static android.graphics.Color.parseColor;
@@ -189,9 +188,7 @@ public class PrepareCreateActivity extends BrandedActivity {
 
             finish();
         } else {
-            // TODO Use snackbar for better error handling
-            DeckLog.error("Selected account at position " + binding.accountSelect.getSelectedItemPosition() + " is null.");
-            Toast.makeText(this, R.string.error, Toast.LENGTH_LONG).show();
+            ExceptionDialogFragment.newInstance(new IllegalStateException("Selected account at position " + binding.accountSelect.getSelectedItemPosition() + " is null."), null).show(getSupportFragmentManager(), ExceptionDialogFragment.class.getSimpleName());
         }
     }
 
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/stack/StackFragment.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/stack/StackFragment.java
index def22c3f7..7b43d130c 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/ui/stack/StackFragment.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/stack/StackFragment.java
@@ -66,7 +66,7 @@ public class StackFragment extends BrandedFragment implements DragAndDropTab<Car
 
         syncManager = new SyncManager(activity);
 
-        adapter = new CardAdapter(requireContext(), mainViewModel.getCurrentAccount(), mainViewModel.getCurrentBoardLocalId(), stackId, mainViewModel.currentBoardHasEditPermission(), syncManager, this, (requireActivity() instanceof SelectCardListener) ? (SelectCardListener) requireActivity() : null);
+        adapter = new CardAdapter(requireContext(), getChildFragmentManager(), mainViewModel.getCurrentAccount(), mainViewModel.getCurrentBoardLocalId(), stackId, mainViewModel.currentBoardHasEditPermission(), syncManager, this, (requireActivity() instanceof SelectCardListener) ? (SelectCardListener) requireActivity() : null);
         binding.recyclerView.setAdapter(adapter);
 
         if (onScrollListener != null) {
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/singlecard/SelectCardForWidgetActivity.java b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/singlecard/SelectCardForWidgetActivity.java
new file mode 100644
index 000000000..e87e9c955
--- /dev/null
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/singlecard/SelectCardForWidgetActivity.java
@@ -0,0 +1,67 @@
+package it.niedermann.nextcloud.deck.ui.widget.singlecard;
+
+import android.appwidget.AppWidgetManager;
+import android.content.Intent;
+import android.os.Bundle;
+import android.view.Menu;
+import android.view.View;
+
+import androidx.annotation.NonNull;
+
+import it.niedermann.nextcloud.deck.R;
+import it.niedermann.nextcloud.deck.model.Board;
+import it.niedermann.nextcloud.deck.model.full.FullCard;
+import it.niedermann.nextcloud.deck.ui.MainActivity;
+import it.niedermann.nextcloud.deck.ui.card.SelectCardListener;
+
+public class SelectCardForWidgetActivity extends MainActivity implements SelectCardListener {
+
+    private int appWidgetId;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        final Intent intent = getIntent();
+        if (intent == null) {
+            finish();
+            return;
+        }
+        final Bundle args = intent.getExtras();
+        if (args == null) {
+            finish();
+            return;
+        }
+        appWidgetId = args.getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, AppWidgetManager.INVALID_APPWIDGET_ID);
+        if (appWidgetId == AppWidgetManager.INVALID_APPWIDGET_ID) {
+            finish();
+        }
+    }
+
+    @Override
+    public void onCardSelected(FullCard fullCard) {
+        syncManager.addOrUpdateSingleCardWidget(appWidgetId, mainViewModel.getCurrentAccount().getId(), mainViewModel.getCurrentBoardLocalId(), fullCard.getLocalId());
+        final Intent updateIntent = new Intent(AppWidgetManager.ACTION_APPWIDGET_UPDATE, null,
+                getApplicationContext(), SingleCardWidget.class)
+                .putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);
+        setResult(RESULT_OK, updateIntent);
+        getApplicationContext().sendBroadcast(updateIntent);
+        finish();
+    }
+
+    @Override
+    protected void setCurrentBoard(@NonNull Board board) {
+        super.setCurrentBoard(board);
+        binding.addStackButton.setVisibility(View.GONE);
+        binding.fab.setVisibility(View.GONE);
+        binding.toolbar.setTitle(R.string.simple_select);
+    }
+
+    @Override
+    protected void showFabIfEditPermissionGranted() { /* Silence is gold */ }
+
+    @Override
+    public boolean onCreateOptionsMenu(Menu menu) {
+        return true;
+    }
+
+}
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
new file mode 100644
index 000000000..783f98e00
--- /dev/null
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/ui/widget/singlecard/SingleCardWidget.java
@@ -0,0 +1,153 @@
+package it.niedermann.nextcloud.deck.ui.widget.singlecard;
+
+import android.app.PendingIntent;
+import android.appwidget.AppWidgetManager;
+import android.appwidget.AppWidgetProvider;
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.Intent;
+import android.os.Build;
+import android.view.View;
+import android.widget.RemoteViews;
+
+import androidx.annotation.DrawableRes;
+import androidx.annotation.IdRes;
+import androidx.annotation.NonNull;
+
+import java.util.NoSuchElementException;
+
+import it.niedermann.nextcloud.deck.R;
+import it.niedermann.nextcloud.deck.model.Card;
+import it.niedermann.nextcloud.deck.model.full.FullSingleCardWidgetModel;
+import it.niedermann.nextcloud.deck.persistence.sync.SyncManager;
+import it.niedermann.nextcloud.deck.ui.card.EditActivity;
+import it.niedermann.nextcloud.deck.util.DateUtil;
+
+public class SingleCardWidget extends AppWidgetProvider {
+
+    void updateAppWidget(Context context, AppWidgetManager awm, int[] appWidgetIds) {
+        final SyncManager syncManager = new SyncManager(context);
+
+        for (int appWidgetId : appWidgetIds) {
+            new Thread(() -> {
+                try {
+                    final FullSingleCardWidgetModel fullModel = syncManager.getSingleCardWidgetModelDirectly(appWidgetId);
+
+                    final Intent intent = EditActivity.createEditCardIntent(context, fullModel.getAccount(), fullModel.getModel().getBoardId(), fullModel.getFullCard().getLocalId());
+                    final PendingIntent pendingIntent = PendingIntent.getActivity(context, appWidgetId, intent, PendingIntent.FLAG_UPDATE_CURRENT);
+                    final RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.widget_single_card);
+
+                    views.setOnClickPendingIntent(R.id.widget_card, pendingIntent);
+
+                    views.setTextViewText(R.id.title, fullModel.getFullCard().getCard().getTitle());
+                    views.setTextViewText(R.id.description, fullModel.getFullCard().getCard().getDescription());
+
+                    if (fullModel.getFullCard().getCard().getDueDate() != null) {
+                        views.setTextViewText(R.id.card_due_date, DateUtil.getRelativeDateTimeString(context, fullModel.getFullCard().getCard().getDueDate().getTime()));
+                        // TODO Use multiple views for background colors and only set the necessary to View.VISIBLE
+                        // https://stackoverflow.com/a/3376537
+                        // Because otherwise using Reflection is the only way
+                        views.setViewVisibility(R.id.card_due_date, View.VISIBLE);
+                        views.setViewVisibility(R.id.card_due_date_image, View.VISIBLE);
+                        setImageDrawable(views, R.id.card_due_date_image, R.drawable.calendar_blank_grey600_24dp);
+                    } else {
+                        views.setViewVisibility(R.id.card_due_date, View.GONE);
+                        views.setViewVisibility(R.id.card_due_date_image, View.GONE);
+                    }
+
+
+                    final String counterMaxValue = context.getString(R.string.counter_max_value);
+
+                    final int attachmentsCount = fullModel.getFullCard().getAttachments().size();
+                    if (attachmentsCount == 0) {
+                        views.setViewVisibility(R.id.card_count_attachments, View.GONE);
+                        views.setViewVisibility(R.id.card_count_attachments_image, View.GONE);
+                    } else {
+                        views.setViewVisibility(R.id.card_count_attachments, View.VISIBLE);
+                        views.setViewVisibility(R.id.card_count_attachments_image, View.VISIBLE);
+                        setupCounter(views, R.id.card_count_attachments, attachmentsCount, counterMaxValue);
+                        setImageDrawable(views, R.id.card_count_attachments_image, R.drawable.ic_check_grey600_24dp);
+                    }
+
+                    final int commentsCount = fullModel.getFullCard().getCommentCount();
+                    if (commentsCount == 0) {
+                        views.setViewVisibility(R.id.card_count_comments, View.GONE);
+                        views.setViewVisibility(R.id.card_count_comments_image, View.GONE);
+                    } else {
+                        views.setViewVisibility(R.id.card_count_comments, View.VISIBLE);
+                        views.setViewVisibility(R.id.card_count_comments_image, View.VISIBLE);
+                        setupCounter(views, R.id.card_count_comments, commentsCount, counterMaxValue);
+                        setImageDrawable(views, R.id.card_count_comments_image, R.drawable.ic_comment_white_24dp);
+                    }
+
+                    final Card.TaskStatus taskStatus = fullModel.getFullCard().getCard().getTaskStatus();
+                    if (taskStatus.taskCount > 0) {
+                        views.setViewVisibility(R.id.card_count_tasks, View.VISIBLE);
+                        views.setViewVisibility(R.id.card_count_tasks_image, View.VISIBLE);
+                        views.setTextViewText(R.id.card_count_tasks, context.getResources().getString(R.string.task_count, String.valueOf(taskStatus.doneCount), String.valueOf(taskStatus.taskCount)));
+                        setImageDrawable(views, R.id.card_count_tasks_image, R.drawable.ic_attach_file_grey600_24dp);
+                    } else {
+                        views.setViewVisibility(R.id.card_count_tasks, View.GONE);
+                        views.setViewVisibility(R.id.card_count_tasks_image, View.GONE);
+                    }
+
+                    awm.updateAppWidget(appWidgetId, views);
+                } catch (NoSuchElementException e) {
+                    // onUpdate has been triggered before the user finished configuring the widget
+                }
+            }).start();
+        }
+    }
+
+    private static void setupCounter(@NonNull RemoteViews views, @IdRes int textViewId, int count, String counterMaxValue) {
+        if (count > 99) {
+            views.setTextViewText(textViewId, counterMaxValue);
+        } else if (count > 1 || Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
+            views.setTextViewText(textViewId, String.valueOf(count));
+        } else if (count == 1) {
+            views.setTextViewText(textViewId, "");
+        }
+    }
+
+    private static void setImageDrawable(@NonNull RemoteViews views, @IdRes int imageView, @DrawableRes int image) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            views.setImageViewResource(imageView, image);
+        }
+    }
+
+    @Override
+    public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
+        super.onUpdate(context, appWidgetManager, appWidgetIds);
+        updateAppWidget(context, appWidgetManager, appWidgetIds);
+    }
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        super.onReceive(context, intent);
+        AppWidgetManager awm = AppWidgetManager.getInstance(context);
+
+        updateAppWidget(context, AppWidgetManager.getInstance(context),
+                (awm.getAppWidgetIds(new ComponentName(context, SingleCardWidget.class))));
+    }
+
+    @Override
+    public void onDeleted(Context context, int[] appWidgetIds) {
+        final SyncManager syncManager = new SyncManager(context);
+
+        for (int appWidgetId : appWidgetIds) {
+            syncManager.deleteSingleCardWidgetModel(appWidgetId);
+        }
+
+        super.onDeleted(context, appWidgetIds);
+    }
+
+
+    /**
+     * Updates UI data of all {@link SingleCardWidget} instances
+     */
+    public static void notifyDatasetChanged(Context context) {
+        Intent intent = new Intent(context, SingleCardWidget.class);
+        intent.setAction("android.appwidget.action.APPWIDGET_UPDATE");
+        context.sendBroadcast(intent);
+    }
+}