Merge branch 'master' into 354-password-protection

# Conflicts:
#	app/src/main/java/it/niedermann/owncloud/notes/android/fragment/PreferencesFragment.java
#	app/src/main/res/values/strings.xml

19 files changed, 444 insertions, 234 deletions

diff --git a/app/src/main/java/it/niedermann/owncloud/notes/android/MultiSelectedActionModeCallback.java b/app/src/main/java/it/niedermann/owncloud/notes/android/MultiSelectedActionModeCallback.java
index 46b0fa69..96ccb878 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/android/MultiSelectedActionModeCallback.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/android/MultiSelectedActionModeCallback.java
@@ -12,6 +12,10 @@ import androidx.fragment.app.FragmentManager;
 import androidx.recyclerview.widget.RecyclerView;
 
 import com.google.android.material.snackbar.Snackbar;
+import com.nextcloud.android.sso.exceptions.NextcloudFilesAppAccountNotFoundException;
+import com.nextcloud.android.sso.exceptions.NoCurrentAccountSelectedException;
+import com.nextcloud.android.sso.helper.SingleAccountHelper;
+import com.nextcloud.android.sso.model.SingleSignOnAccount;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -70,34 +74,39 @@ public class MultiSelectedActionModeCallback implements Callback {
     public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
         switch (item.getItemId()) {
             case R.id.menu_delete: {
-                List<DBNote> deletedNotes = new ArrayList<>();
-                List<Integer> selection = adapter.getSelected();
-                for (Integer i : selection) {
-                    DBNote note = (DBNote) adapter.getItem(i);
-                    deletedNotes.add(db.getNote(note.getAccountId(), note.getId()));
-                    db.deleteNoteAndSync(note.getId());
+                try {
+                    SingleSignOnAccount ssoAccount = SingleAccountHelper.getCurrentSingleSignOnAccount(context);
+                    List<DBNote> deletedNotes = new ArrayList<>();
+                    List<Integer> selection = adapter.getSelected();
+                    for (Integer i : selection) {
+                        DBNote note = (DBNote) adapter.getItem(i);
+                        deletedNotes.add(db.getNote(note.getAccountId(), note.getId()));
+                        db.deleteNoteAndSync(ssoAccount, note.getId());
+                    }
+                    mode.finish(); // Action picked, so close the CAB
+                    //after delete selection has to be cleared
+                    searchView.setIconified(true);
+                    refreshLists.run();
+                    String deletedSnackbarTitle = deletedNotes.size() == 1
+                            ? context.getString(R.string.action_note_deleted, deletedNotes.get(0).getTitle())
+                            : context.getString(R.string.bulk_notes_deleted, deletedNotes.size());
+                    Snackbar.make(viewProvider.getView(), deletedSnackbarTitle, Snackbar.LENGTH_LONG)
+                            .setAction(R.string.action_undo, (View v) -> {
+                                db.getNoteServerSyncHelper().addCallbackPush(ssoAccount, refreshLists::run);
+                                for (DBNote deletedNote : deletedNotes) {
+                                    db.addNoteAndSync(ssoAccount, deletedNote.getAccountId(), deletedNote);
+                                }
+                                refreshLists.run();
+                                String restoreSnackbarTitle = deletedNotes.size() == 1
+                                        ? context.getString(R.string.action_note_restored, deletedNotes.get(0).getTitle())
+                                        : context.getString(R.string.bulk_notes_restored, deletedNotes.size());
+                                Snackbar.make(viewProvider.getView(), restoreSnackbarTitle, Snackbar.LENGTH_SHORT)
+                                        .show();
+                            })
+                            .show();
+                } catch (NextcloudFilesAppAccountNotFoundException | NoCurrentAccountSelectedException e) {
+                    e.printStackTrace();
                 }
-                mode.finish(); // Action picked, so close the CAB
-                //after delete selection has to be cleared
-                searchView.setIconified(true);
-                refreshLists.run();
-                String deletedSnackbarTitle = deletedNotes.size() == 1
-                        ? context.getString(R.string.action_note_deleted, deletedNotes.get(0).getTitle())
-                        : context.getString(R.string.bulk_notes_deleted, deletedNotes.size());
-                Snackbar.make(viewProvider.getView(), deletedSnackbarTitle, Snackbar.LENGTH_LONG)
-                        .setAction(R.string.action_undo, (View v) -> {
-                            db.getNoteServerSyncHelper().addCallbackPush(refreshLists::run);
-                            for (DBNote deletedNote : deletedNotes) {
-                                db.addNoteAndSync(deletedNote.getAccountId(), deletedNote);
-                            }
-                            refreshLists.run();
-                            String restoreSnackbarTitle = deletedNotes.size() == 1
-                                    ? context.getString(R.string.action_note_restored, deletedNotes.get(0).getTitle())
-                                    : context.getString(R.string.bulk_notes_restored, deletedNotes.size());
-                            Snackbar.make(viewProvider.getView(), restoreSnackbarTitle, Snackbar.LENGTH_SHORT)
-                                    .show();
-                        })
-                        .show();
                 return true;
             }
             case R.id.menu_move: {
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/android/NotesListViewItemTouchHelper.java b/app/src/main/java/it/niedermann/owncloud/notes/android/NotesListViewItemTouchHelper.java
index 63de4b70..3e851ba5 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/android/NotesListViewItemTouchHelper.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/android/NotesListViewItemTouchHelper.java
@@ -10,19 +10,21 @@ import androidx.recyclerview.widget.ItemTouchHelper;
 import androidx.recyclerview.widget.RecyclerView;
 
 import com.google.android.material.snackbar.Snackbar;
+import com.nextcloud.android.sso.model.SingleSignOnAccount;
 
 import it.niedermann.owncloud.notes.R;
 import it.niedermann.owncloud.notes.model.DBNote;
+import it.niedermann.owncloud.notes.model.ISyncCallback;
 import it.niedermann.owncloud.notes.model.ItemAdapter;
 import it.niedermann.owncloud.notes.persistence.NoteSQLiteOpenHelper;
 import it.niedermann.owncloud.notes.persistence.NoteServerSyncHelper.ViewProvider;
-import it.niedermann.owncloud.notes.model.ISyncCallback;
 
 public class NotesListViewItemTouchHelper extends ItemTouchHelper {
 
     private static final String TAG = NotesListViewItemTouchHelper.class.getCanonicalName();
 
     public NotesListViewItemTouchHelper(
+            SingleSignOnAccount ssoAccount,
             Context context,
             ViewProvider viewProvider,
             NoteSQLiteOpenHelper db,
@@ -61,14 +63,14 @@ public class NotesListViewItemTouchHelper extends ItemTouchHelper {
                     case ItemTouchHelper.LEFT: {
                         final DBNote dbNoteWithoutContent = (DBNote) adapter.getItem(viewHolder.getAdapterPosition());
                         final DBNote dbNote = db.getNote(dbNoteWithoutContent.getAccountId(), dbNoteWithoutContent.getId());
-                        db.deleteNoteAndSync(dbNote.getId());
+                        db.deleteNoteAndSync(ssoAccount, dbNote.getId());
                         adapter.remove(dbNote);
                         refreshLists.run();
                         Log.v(TAG, "Item deleted through swipe ----------------------------------------------");
                         Snackbar.make(viewProvider.getView(), context.getString(R.string.action_note_deleted, dbNote.getTitle()), Snackbar.LENGTH_LONG)
                                 .setAction(R.string.action_undo, (View v) -> {
-                                    db.getNoteServerSyncHelper().addCallbackPush(refreshLists::run);
-                                    db.addNoteAndSync(dbNote.getAccountId(), dbNote);
+                                    db.getNoteServerSyncHelper().addCallbackPush(ssoAccount, refreshLists::run);
+                                    db.addNoteAndSync(ssoAccount, dbNote.getAccountId(), dbNote);
                                     refreshLists.run();
                                     Snackbar.make(viewProvider.getView(), context.getString(R.string.action_note_restored, dbNote.getTitle()), Snackbar.LENGTH_SHORT)
                                             .show();
@@ -78,7 +80,7 @@ public class NotesListViewItemTouchHelper extends ItemTouchHelper {
                     }
                     case ItemTouchHelper.RIGHT: {
                         final DBNote dbNote = (DBNote) adapter.getItem(viewHolder.getAdapterPosition());
-                        db.toggleFavorite(dbNote, syncCallBack);
+                        db.toggleFavorite(ssoAccount, dbNote, syncCallBack);
                         refreshLists.run();
                         break;
                     }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/android/activity/EditNoteActivity.java b/app/src/main/java/it/niedermann/owncloud/notes/android/activity/EditNoteActivity.java
index 4441b720..8d95f018 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/android/activity/EditNoteActivity.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/android/activity/EditNoteActivity.java
@@ -261,7 +261,7 @@ public class EditNoteActivity extends LockedActivity implements BaseNoteFragment
             }
         } else {
             // Maybe account is not authenticated -> note == null
-            Log.e(TAG, "note is null, start NotesListViewActivity");
+            Log.e(TAG, "note is null, start " + NotesListViewActivity.class.getSimpleName());
             startActivity(new Intent(this, NotesListViewActivity.class));
             finish();
         }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/android/activity/NotesListViewActivity.java b/app/src/main/java/it/niedermann/owncloud/notes/android/activity/NotesListViewActivity.java
index db842340..fcac49d5 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/android/activity/NotesListViewActivity.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/android/activity/NotesListViewActivity.java
@@ -96,6 +96,7 @@ public class NotesListViewActivity extends LockedActivity implements ItemAdapter
      */
     private boolean notAuthorizedAccountHandled = false;
 
+    private SingleSignOnAccount ssoAccount;
     private LocalAccount localAccount;
 
     @BindView(R.id.coordinatorLayout)
@@ -182,23 +183,27 @@ public class NotesListViewActivity extends LockedActivity implements ItemAdapter
     @Override
     protected void onResume() {
         try {
-            String ssoAccount = SingleAccountHelper.getCurrentSingleSignOnAccount(getApplicationContext()).name;
-            if (localAccount == null || !localAccount.getAccountName().equals(ssoAccount)) {
-                selectAccount(SingleAccountHelper.getCurrentSingleSignOnAccount(getApplicationContext()).name);
+            ssoAccount = SingleAccountHelper.getCurrentSingleSignOnAccount(getApplicationContext());
+            if (localAccount == null || !localAccount.getAccountName().equals(ssoAccount.name)) {
+                selectAccount(ssoAccount.name);
             }
         } catch (NoCurrentAccountSelectedException | NextcloudFilesAppAccountNotFoundException e) {
+            if (localAccount == null) {
+                List<LocalAccount> localAccounts = db.getAccounts();
+                if (localAccounts.size() > 0) {
+                    localAccount = localAccounts.get(0);
+                }
+            }
             if (!notAuthorizedAccountHandled) {
                 handleNotAuthorizedAccount();
             }
         }
 
         // refresh and sync every time the activity gets
+        refreshLists();
         if (localAccount != null) {
-            refreshLists();
-            db.getNoteServerSyncHelper().addCallbackPull(syncCallBack);
-            if (db.getNoteServerSyncHelper().isSyncPossible()) {
-                synchronize();
-            }
+            synchronize();
+            db.getNoteServerSyncHelper().addCallbackPull(ssoAccount, syncCallBack);
         }
         super.onResume();
     }
@@ -230,13 +235,14 @@ public class NotesListViewActivity extends LockedActivity implements ItemAdapter
         SingleAccountHelper.setCurrentAccount(getApplicationContext(), accountName);
         localAccount = db.getLocalAccountByAccountName(accountName);
         try {
-            db.getNoteServerSyncHelper().updateAccount();
+            ssoAccount = SingleAccountHelper.getCurrentSingleSignOnAccount(getApplicationContext());
             synchronize();
-            refreshLists();
-            fabCreate.show();
-        } catch (NextcloudFilesAppAccountNotFoundException e) {
+        } catch (NextcloudFilesAppAccountNotFoundException | NoCurrentAccountSelectedException e) {
+            Log.i(TAG, "Tried to select account, but got an " + e.getClass().getSimpleName() + ". Asking for importing an account...");
             handleNotAuthorizedAccount();
         }
+        refreshLists();
+        fabCreate.show();
         setupHeader();
         setupNavigationList(ADAPTER_KEY_RECENT);
         updateUsernameInDrawer();
@@ -312,13 +318,12 @@ public class NotesListViewActivity extends LockedActivity implements ItemAdapter
             }
         });
 
-        // Pull to Refresh
         swipeRefreshLayout.setOnRefreshListener(() -> {
-            if (db.getNoteServerSyncHelper().isSyncPossible()) {
-                synchronize();
-            } else {
+            if (ssoAccount == null) {
                 swipeRefreshLayout.setRefreshing(false);
-                Snackbar.make(coordinatorLayout, getString(R.string.error_sync, getString(LoginStatus.NO_NETWORK.str)), Snackbar.LENGTH_LONG).show();
+                askForNewAccount(this);
+            } else {
+                synchronize();
             }
         });
 
@@ -529,7 +534,7 @@ public class NotesListViewActivity extends LockedActivity implements ItemAdapter
         adapter = new ItemAdapter(this);
         listView.setAdapter(adapter);
         listView.setLayoutManager(new LinearLayoutManager(this));
-        new NotesListViewItemTouchHelper(this, this, db, adapter, syncCallBack, this::refreshLists).attachToRecyclerView(listView);
+        new NotesListViewItemTouchHelper(ssoAccount, this, this, db, adapter, syncCallBack, this::refreshLists).attachToRecyclerView(listView);
     }
 
     private void refreshLists() {
@@ -775,7 +780,7 @@ public class NotesListViewActivity extends LockedActivity implements ItemAdapter
     public void onNoteFavoriteClick(int position, View view) {
         DBNote note = (DBNote) adapter.getItem(position);
         NoteSQLiteOpenHelper db = NoteSQLiteOpenHelper.getInstance(view.getContext());
-        db.toggleFavorite(note, syncCallBack);
+        db.toggleFavorite(ssoAccount, note, syncCallBack);
         adapter.notifyItemChanged(position);
         refreshLists();
     }
@@ -804,11 +809,23 @@ public class NotesListViewActivity extends LockedActivity implements ItemAdapter
     }
 
     private void synchronize() {
-        swipeRefreshLayout.setRefreshing(true);
-        db.getNoteServerSyncHelper().addCallbackPull(syncCallBack);
-        db.getNoteServerSyncHelper().scheduleSync(false);
+        NoteServerSyncHelper syncHelper = db.getNoteServerSyncHelper();
+        if (syncHelper.isSyncPossible()) {
+            swipeRefreshLayout.setRefreshing(true);
+            syncHelper.addCallbackPull(ssoAccount, syncCallBack);
+            syncHelper.scheduleSync(ssoAccount, false);
+        } else { // Sync is not possible
+            swipeRefreshLayout.setRefreshing(false);
+            if (syncHelper.isNetworkConnected() && syncHelper.isSyncOnlyOnWifi()) {
+                Log.d(TAG, "Network is connected, but sync is not possible");
+            } else {
+                Log.d(TAG, "Sync is not possible, because network is not connected");
+                Snackbar.make(coordinatorLayout, getString(R.string.error_sync, getString(LoginStatus.NO_NETWORK.str)), Snackbar.LENGTH_LONG).show();
+            }
+        }
     }
 
+
     @Override
     public void onAccountChosen(LocalAccount account) {
         List<Integer> selection = new ArrayList<>(adapter.getSelected());
@@ -816,7 +833,7 @@ public class NotesListViewActivity extends LockedActivity implements ItemAdapter
         adapter.deselect(0);
         for (Integer i : selection) {
             DBNote note = (DBNote) adapter.getItem(i);
-            db.moveNoteToAnotherAccount(note.getAccountId(), db.getNote(note.getAccountId(), note.getId()), account.getId());
+            db.moveNoteToAnotherAccount(ssoAccount, note.getAccountId(), db.getNote(note.getAccountId(), note.getId()), account.getId());
             RecyclerView.ViewHolder viewHolder = listView.findViewHolderForAdapterPosition(i);
             if (viewHolder != null) {
                 viewHolder.itemView.setSelected(false);
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/BaseNoteFragment.java b/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/BaseNoteFragment.java
index 529e5c03..2f42bc8d 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/BaseNoteFragment.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/BaseNoteFragment.java
@@ -24,6 +24,7 @@ import androidx.fragment.app.FragmentManager;
 import com.nextcloud.android.sso.exceptions.NextcloudFilesAppAccountNotFoundException;
 import com.nextcloud.android.sso.exceptions.NoCurrentAccountSelectedException;
 import com.nextcloud.android.sso.helper.SingleAccountHelper;
+import com.nextcloud.android.sso.model.SingleSignOnAccount;
 
 import java.util.Objects;
 
@@ -33,9 +34,9 @@ import it.niedermann.owncloud.notes.android.fragment.CategoryDialogFragment.Cate
 import it.niedermann.owncloud.notes.model.CloudNote;
 import it.niedermann.owncloud.notes.model.DBNote;
 import it.niedermann.owncloud.notes.model.DBStatus;
+import it.niedermann.owncloud.notes.model.ISyncCallback;
 import it.niedermann.owncloud.notes.model.LocalAccount;
 import it.niedermann.owncloud.notes.persistence.NoteSQLiteOpenHelper;
-import it.niedermann.owncloud.notes.model.ISyncCallback;
 import it.niedermann.owncloud.notes.util.NoteUtil;
 
 import static androidx.core.content.pm.ShortcutManagerCompat.isRequestPinShortcutSupported;
@@ -54,6 +55,7 @@ public abstract class BaseNoteFragment extends Fragment implements CategoryDialo
     private static final String SAVEDKEY_ORIGINAL_NOTE = "original_note";
 
     private LocalAccount localAccount;
+    private SingleSignOnAccount ssoAccount;
 
     protected DBNote note;
     @Nullable
@@ -67,7 +69,8 @@ public abstract class BaseNoteFragment extends Fragment implements CategoryDialo
     public void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         try {
-            this.localAccount = db.getLocalAccountByAccountName(SingleAccountHelper.getCurrentSingleSignOnAccount(getActivity().getApplicationContext()).name);
+            this.ssoAccount = SingleAccountHelper.getCurrentSingleSignOnAccount(getActivity().getApplicationContext());
+            this.localAccount = db.getLocalAccountByAccountName(ssoAccount.name);
 
             if (savedInstanceState == null) {
                 long id = getArguments().getLong(PARAM_NOTE_ID);
@@ -77,11 +80,6 @@ public abstract class BaseNoteFragment extends Fragment implements CategoryDialo
                         /* Switch account if account id has been provided */
                         this.localAccount = db.getAccount(accountId);
                         SingleAccountHelper.setCurrentAccount(getActivity().getApplicationContext(), localAccount.getAccountName());
-                        try {
-                            db.getNoteServerSyncHelper().updateAccount();
-                        } catch (NextcloudFilesAppAccountNotFoundException e) {
-                            e.printStackTrace();
-                        }
                     }
                     isNew = false;
                     note = originalNote = db.getNote(localAccount.getId(), id);
@@ -95,7 +93,7 @@ public abstract class BaseNoteFragment extends Fragment implements CategoryDialo
                             note = new DBNote(-1, -1, null, NoteUtil.generateNoteTitle(content), content, false, getString(R.string.category_readonly), null, DBStatus.VOID, -1, "");
                         }
                     } else {
-                        note = db.getNote(localAccount.getId(), db.addNoteAndSync(localAccount.getId(), cloudNote));
+                        note = db.getNote(localAccount.getId(), db.addNoteAndSync(ssoAccount, localAccount.getId(), cloudNote));
                         originalNote = null;
                     }
                 }
@@ -177,18 +175,18 @@ public abstract class BaseNoteFragment extends Fragment implements CategoryDialo
         switch (item.getItemId()) {
             case R.id.menu_cancel:
                 if (originalNote == null) {
-                    db.deleteNoteAndSync(note.getId());
+                    db.deleteNoteAndSync(ssoAccount, note.getId());
                 } else {
-                    db.updateNoteAndSync(localAccount.getId(), originalNote, null, null);
+                    db.updateNoteAndSync(ssoAccount, localAccount.getId(), originalNote, null, null);
                 }
                 listener.close();
                 return true;
             case R.id.menu_delete:
-                db.deleteNoteAndSync(note.getId());
+                db.deleteNoteAndSync(ssoAccount, note.getId());
                 listener.close();
                 return true;
             case R.id.menu_favorite:
-                db.toggleFavorite(note, null);
+                db.toggleFavorite(ssoAccount, note, null);
                 listener.onNoteUpdated(note);
                 prepareFavoriteOption(item);
                 return true;
@@ -248,7 +246,7 @@ public abstract class BaseNoteFragment extends Fragment implements CategoryDialo
 
     public void onCloseNote() {
         if (originalNote == null && getContent().isEmpty()) {
-            db.deleteNoteAndSync(note.getId());
+            db.deleteNoteAndSync(ssoAccount, note.getId());
         }
     }
 
@@ -264,7 +262,7 @@ public abstract class BaseNoteFragment extends Fragment implements CategoryDialo
             if (note.getContent().equals(newContent)) {
                 Log.v(TAG, "... not saving, since nothing has changed");
             } else {
-                note = db.updateNoteAndSync(localAccount.getId(), note, newContent, callback);
+                note = db.updateNoteAndSync(ssoAccount, localAccount.getId(), note, newContent, callback);
                 listener.onNoteUpdated(note);
             }
         } else {
@@ -310,12 +308,12 @@ public abstract class BaseNoteFragment extends Fragment implements CategoryDialo
 
     @Override
     public void onCategoryChosen(String category) {
-        db.setCategory(note, category, null);
+        db.setCategory(ssoAccount, note, category, null);
         listener.onNoteUpdated(note);
     }
 
     public void moveNote(LocalAccount account) {
-        db.moveNoteToAnotherAccount(note.getAccountId(), note, account.getId());
+        db.moveNoteToAnotherAccount(ssoAccount, note.getAccountId(), note, account.getId());
         listener.close();
     }
 
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/NotePreviewFragment.java b/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/NotePreviewFragment.java
index 5cdeb25f..c85eb8a0 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/NotePreviewFragment.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/NotePreviewFragment.java
@@ -26,6 +26,10 @@ import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout.OnRefreshListener;
 
 import com.google.android.material.floatingactionbutton.FloatingActionButton;
+import com.nextcloud.android.sso.exceptions.NextcloudFilesAppAccountNotFoundException;
+import com.nextcloud.android.sso.exceptions.NoCurrentAccountSelectedException;
+import com.nextcloud.android.sso.helper.SingleAccountHelper;
+import com.nextcloud.android.sso.model.SingleSignOnAccount;
 import com.yydcdut.markdown.MarkdownProcessor;
 import com.yydcdut.markdown.MarkdownTextView;
 import com.yydcdut.markdown.syntax.text.TextFactory;
@@ -41,6 +45,7 @@ import it.niedermann.owncloud.notes.persistence.NoteSQLiteOpenHelper;
 import it.niedermann.owncloud.notes.util.DisplayUtils;
 import it.niedermann.owncloud.notes.util.MarkDownUtil;
 import it.niedermann.owncloud.notes.util.NoteLinksUtils;
+import it.niedermann.owncloud.notes.util.SSOUtil;
 
 public class NotePreviewFragment extends SearchableBaseNoteFragment implements OnRefreshListener {
 
@@ -206,14 +211,19 @@ public class NotePreviewFragment extends SearchableBaseNoteFragment implements O
 
     @Override
     public void onRefresh() {
-        if (db.getNoteServerSyncHelper().isSyncPossible()) {
+        if (db.getNoteServerSyncHelper().isSyncPossible() && SSOUtil.isConfigured(getContext())) {
             swipeRefreshLayout.setRefreshing(true);
-            db.getNoteServerSyncHelper().addCallbackPull(() -> {
-                note = db.getNote(note.getAccountId(), note.getId());
-                noteContent.setText(markdownProcessor.parse(NoteLinksUtils.replaceNoteLinksWithDummyUrls(note.getContent(), db.getRemoteIds(note.getAccountId()))));
-                swipeRefreshLayout.setRefreshing(false);
-            });
-            db.getNoteServerSyncHelper().scheduleSync(false);
+            try {
+                SingleSignOnAccount ssoAccount = SingleAccountHelper.getCurrentSingleSignOnAccount(getContext());
+                db.getNoteServerSyncHelper().addCallbackPull(ssoAccount, () -> {
+                    note = db.getNote(note.getAccountId(), note.getId());
+                    noteContent.setText(markdownProcessor.parse(NoteLinksUtils.replaceNoteLinksWithDummyUrls(note.getContent(), db.getRemoteIds(note.getAccountId()))));
+                    swipeRefreshLayout.setRefreshing(false);
+                });
+                db.getNoteServerSyncHelper().scheduleSync(ssoAccount, false);
+            } catch (NextcloudFilesAppAccountNotFoundException | NoCurrentAccountSelectedException e) {
+                e.printStackTrace();
+            }
         } else {
             swipeRefreshLayout.setRefreshing(false);
             Toast.makeText(getContext(), getString(R.string.error_sync, getString(LoginStatus.NO_NETWORK.str)), Toast.LENGTH_LONG).show();
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/PreferencesFragment.java b/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/PreferencesFragment.java
index 3cddea75..2dd1050f 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/PreferencesFragment.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/android/fragment/PreferencesFragment.java
@@ -5,11 +5,13 @@ import android.os.Bundle;
 import android.util.Log;
 
 import androidx.annotation.Nullable;
+import androidx.preference.ListPreference;
 import androidx.preference.PreferenceFragmentCompat;
 import androidx.preference.SwitchPreference;
 
 import it.niedermann.owncloud.notes.R;
 import it.niedermann.owncloud.notes.util.DeviceCredentialUtil;
+import it.niedermann.owncloud.notes.persistence.SyncWorker;
 import it.niedermann.owncloud.notes.util.Notes;
 
 public class PreferencesFragment extends PreferenceFragmentCompat {
@@ -36,18 +38,26 @@ public class PreferencesFragment extends PreferenceFragmentCompat {
         }
 
         final SwitchPreference themePref = findPreference(getString(R.string.pref_key_theme));
+        assert themePref != null;
         themePref.setOnPreferenceChangeListener((preference, newValue) -> {
-            Boolean darkTheme = (Boolean) newValue;
-            Notes.setAppTheme(darkTheme);
+            Notes.setAppTheme((Boolean) newValue);
             getActivity().setResult(Activity.RESULT_OK);
             getActivity().recreate();
             return true;
         });
 
         final SwitchPreference wifiOnlyPref = findPreference(getString(R.string.pref_key_wifi_only));
+        assert wifiOnlyPref != null;
         wifiOnlyPref.setOnPreferenceChangeListener((preference, newValue) -> {
-            Boolean syncOnWifiOnly = (Boolean) newValue;
-            Log.v(TAG, "syncOnWifiOnly: " + syncOnWifiOnly);
+            Log.v(TAG, "syncOnWifiOnly: " + newValue);
+            return true;
+        });
+
+        final ListPreference syncPref = findPreference(getString(R.string.pref_key_background_sync));
+        assert syncPref != null;
+        syncPref.setOnPreferenceChangeListener((preference, newValue) -> {
+            Log.v(TAG, "syncPref: " + preference + " - newValue: " + newValue);
+            SyncWorker.update(getContext(), newValue.toString());
             return true;
         });
     }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NoteSQLiteOpenHelper.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NoteSQLiteOpenHelper.java
index c0562c73..06c5f0ed 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NoteSQLiteOpenHelper.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NoteSQLiteOpenHelper.java
@@ -24,6 +24,8 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.WorkerThread;
 
+import com.nextcloud.android.sso.model.SingleSignOnAccount;
+
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.ArrayList;
@@ -199,7 +201,7 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
             SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
             String username = sharedPreferences.getString("settingsUsername", "");
             String url = sharedPreferences.getString("settingsUrl", "");
-            if (url != null && url.endsWith("/")) {
+            if (!url.isEmpty() && url.endsWith("/")) {
                 url = url.substring(0, url.length() - 1);
                 try {
                     String accountName = username + "@" + new URL(url).getHost();
@@ -272,7 +274,7 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
                     return;
                 }
             } else {
-                Log.e(TAG, "Previous URL is null. Recreating database...");
+                Log.e(TAG, "Previous URL is empty or does not end with a '/' character. Recreating database...");
                 recreateDatabase(db);
                 return;
             }
@@ -318,11 +320,11 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
      *
      * @param note Note
      */
-    public long addNoteAndSync(long accountId, CloudNote note) {
+    public long addNoteAndSync(SingleSignOnAccount ssoAccount, long accountId, CloudNote note) {
         DBNote dbNote = new DBNote(0, 0, note.getModified(), note.getTitle(), note.getContent(), note.isFavorite(), note.getCategory(), note.getEtag(), DBStatus.LOCAL_EDITED, accountId, NoteUtil.generateNoteExcerpt(note.getContent()));
         long id = addNote(accountId, dbNote);
         notifyNotesChanged();
-        getNoteServerSyncHelper().scheduleSync(true);
+        getNoteServerSyncHelper().scheduleSync(ssoAccount, true);
         return id;
     }
 
@@ -360,13 +362,13 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
         return db.insert(table_notes, null, values);
     }
 
-    public void moveNoteToAnotherAccount(long oldAccountId, DBNote note, long newAccountId) {
+    public void moveNoteToAnotherAccount(SingleSignOnAccount ssoAccount, long oldAccountId, DBNote note, long newAccountId) {
         // Add new note
-        addNoteAndSync(newAccountId, new CloudNote(0, note.getModified(), note.getTitle(), note.getContent(), note.isFavorite(), note.getCategory(), null));
-        deleteNoteAndSync(note.getId());
+        addNoteAndSync(ssoAccount, newAccountId, new CloudNote(0, note.getModified(), note.getTitle(), note.getContent(), note.isFavorite(), note.getCategory(), null));
+        deleteNoteAndSync(ssoAccount, note.getId());
 
         notifyNotesChanged();
-        getNoteServerSyncHelper().scheduleSync(true);
+        getNoteServerSyncHelper().scheduleSync(ssoAccount,true);
     }
 
     /**
@@ -658,7 +660,7 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
         return categories;
     }
 
-    public void toggleFavorite(@NonNull DBNote note, @Nullable ISyncCallback callback) {
+    public void toggleFavorite(SingleSignOnAccount ssoAccount, @NonNull DBNote note, @Nullable ISyncCallback callback) {
         note.setFavorite(!note.isFavorite());
         note.setStatus(DBStatus.LOCAL_EDITED);
         SQLiteDatabase db = this.getWritableDatabase();
@@ -667,12 +669,12 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
         values.put(key_favorite, note.isFavorite() ? "1" : "0");
         db.update(table_notes, values, key_id + " = ?", new String[]{String.valueOf(note.getId())});
         if (callback != null) {
-            serverSyncHelper.addCallbackPush(callback);
+            serverSyncHelper.addCallbackPush(ssoAccount, callback);
         }
-        serverSyncHelper.scheduleSync(true);
+        serverSyncHelper.scheduleSync(ssoAccount, true);
     }
 
-    public void setCategory(@NonNull DBNote note, @NonNull String category, @Nullable ISyncCallback callback) {
+    public void setCategory(SingleSignOnAccount ssoAccount, @NonNull DBNote note, @NonNull String category, @Nullable ISyncCallback callback) {
         note.setCategory(category);
         note.setStatus(DBStatus.LOCAL_EDITED);
         SQLiteDatabase db = this.getWritableDatabase();
@@ -681,9 +683,9 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
         values.put(key_category, note.getCategory());
         db.update(table_notes, values, key_id + " = ?", new String[]{String.valueOf(note.getId())});
         if (callback != null) {
-            serverSyncHelper.addCallbackPush(callback);
+            serverSyncHelper.addCallbackPush(ssoAccount, callback);
         }
-        serverSyncHelper.scheduleSync(true);
+        serverSyncHelper.scheduleSync(ssoAccount,true);
     }
 
     /**
@@ -695,7 +697,7 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
      * @param callback   When the synchronization is finished, this callback will be invoked (optional).
      * @return changed note if differs from database, otherwise the old note.
      */
-    public DBNote updateNoteAndSync(long accountId, @NonNull DBNote oldNote, @Nullable String newContent, @Nullable ISyncCallback callback) {
+    public DBNote updateNoteAndSync(SingleSignOnAccount ssoAccount, long accountId, @NonNull DBNote oldNote, @Nullable String newContent, @Nullable ISyncCallback callback) {
         //debugPrintFullDB();
         DBNote newNote;
         if (newContent == null) {
@@ -716,9 +718,9 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
         if (rows > 0) {
             notifyNotesChanged();
             if (callback != null) {
-                serverSyncHelper.addCallbackPush(callback);
+                serverSyncHelper.addCallbackPush(ssoAccount, callback);
             }
-            serverSyncHelper.scheduleSync(true);
+            serverSyncHelper.scheduleSync(ssoAccount, true);
             return newNote;
         } else {
             if (callback != null) {
@@ -781,7 +783,7 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
      *
      * @param id long - ID of the Note that should be deleted
      */
-    public void deleteNoteAndSync(long id) {
+    public void deleteNoteAndSync(SingleSignOnAccount ssoAccount, long id) {
         SQLiteDatabase db = this.getWritableDatabase();
         ContentValues values = new ContentValues();
         values.put(key_status, DBStatus.LOCAL_DELETED.getTitle());
@@ -790,7 +792,7 @@ public class NoteSQLiteOpenHelper extends SQLiteOpenHelper {
                 key_id + " = ?",
                 new String[]{String.valueOf(id)});
         notifyNotesChanged();
-        getNoteServerSyncHelper().scheduleSync(true);
+        getNoteServerSyncHelper().scheduleSync(ssoAccount, true);
 
         if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
             ShortcutManager shortcutManager = context.getSystemService(ShortcutManager.class);
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NoteServerSyncHelper.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NoteServerSyncHelper.java
index ebea9cb9..6d5c3492 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NoteServerSyncHelper.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NoteServerSyncHelper.java
@@ -15,6 +15,7 @@ import android.util.Log;
 import android.view.View;
 import android.widget.Toast;
 
+import androidx.annotation.NonNull;
 import androidx.appcompat.app.AlertDialog;
 import androidx.appcompat.app.AppCompatActivity;
 
@@ -25,25 +26,29 @@ import com.nextcloud.android.sso.exceptions.NextcloudFilesAppNotSupportedExcepti
 import com.nextcloud.android.sso.exceptions.NextcloudHttpRequestFailedException;
 import com.nextcloud.android.sso.exceptions.NoCurrentAccountSelectedException;
 import com.nextcloud.android.sso.helper.SingleAccountHelper;
+import com.nextcloud.android.sso.model.SingleSignOnAccount;
 
 import org.json.JSONException;
 
 import java.net.ConnectException;
 import java.net.SocketTimeoutException;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 
 import it.niedermann.owncloud.notes.R;
 import it.niedermann.owncloud.notes.model.CloudNote;
 import it.niedermann.owncloud.notes.model.DBNote;
 import it.niedermann.owncloud.notes.model.DBStatus;
+import it.niedermann.owncloud.notes.model.ISyncCallback;
 import it.niedermann.owncloud.notes.model.LocalAccount;
 import it.niedermann.owncloud.notes.model.LoginStatus;
 import it.niedermann.owncloud.notes.util.ExceptionUtil;
-import it.niedermann.owncloud.notes.model.ISyncCallback;
+import it.niedermann.owncloud.notes.util.SSOUtil;
 import it.niedermann.owncloud.notes.util.ServerResponse;
 
 import static android.content.Context.CLIPBOARD_SERVICE;
@@ -59,9 +64,9 @@ public class NoteServerSyncHelper {
 
     private NoteSQLiteOpenHelper db;
     private Context context;
-    private LocalAccount localAccount;
 
     // Track network connection changes using a BroadcastReceiver
+    private boolean isSyncPossible = false;
     private boolean networkConnected = false;
     private String syncOnlyOnWifiKey;
     private boolean syncOnlyOnWifi;
@@ -80,30 +85,29 @@ public class NoteServerSyncHelper {
         @Override
         public void onReceive(Context context, Intent intent) {
             updateNetworkStatus();
-            if (isSyncPossible()) {
-                scheduleSync(false);
+            if (isSyncPossible() && SSOUtil.isConfigured(context)) {
+                try {
+                    scheduleSync(SingleAccountHelper.getCurrentSingleSignOnAccount(context), false);
+                } catch (NextcloudFilesAppAccountNotFoundException | NoCurrentAccountSelectedException e) {
+                    Log.v(TAG, "Can not select current SingleSignOn account after network changed, do not sync.");
+                }
             }
         }
     };
 
     // current state of the synchronization
-    private boolean syncActive = false;
-    private boolean syncScheduled = false;
+    private Map<String, Boolean> syncActive = new HashMap<>();
+    private Map<String, Boolean> syncScheduled = new HashMap<>();
     private NotesClient notesClient;
 
     // list of callbacks for both parts of synchronziation
-    private List<ISyncCallback> callbacksPush = new ArrayList<>();
-    private List<ISyncCallback> callbacksPull = new ArrayList<>();
-
+    private Map<String, List<ISyncCallback>> callbacksPush = new HashMap<>();
+    private Map<String, List<ISyncCallback>> callbacksPull = new HashMap<>();
 
     private NoteServerSyncHelper(NoteSQLiteOpenHelper db) {
         this.db = db;
         this.context = db.getContext();
-        try {
-            updateAccount();
-        } catch (NextcloudFilesAppAccountNotFoundException e) {
-            e.printStackTrace();
-        }
+        notesClient = new NotesClient(context.getApplicationContext());
         this.syncOnlyOnWifiKey = context.getApplicationContext().getResources().getString(R.string.pref_key_wifi_only);
 
         // Registers BroadcastReceiver to track network connection changes.
@@ -131,50 +135,32 @@ public class NoteServerSyncHelper {
         return instance;
     }
 
-    public void updateAccount() throws NextcloudFilesAppAccountNotFoundException {
-        try {
-            this.localAccount = db.getLocalAccountByAccountName(SingleAccountHelper.getCurrentSingleSignOnAccount(context.getApplicationContext()).name);
-            if (notesClient == null) {
-                if (this.localAccount != null) {
-                    notesClient = new NotesClient(context.getApplicationContext());
-                }
-            } else {
-                notesClient.updateAccount();
-            }
-            Log.v(TAG, "NextcloudRequest account: " + localAccount);
-        } catch (NoCurrentAccountSelectedException e) {
-            e.printStackTrace();
-        }
-        Log.v(TAG, "Reinstanziation NotesClient because of SSO acc changed");
-    }
-
     @Override
     protected void finalize() throws Throwable {
         context.getApplicationContext().unregisterReceiver(networkReceiver);
         super.finalize();
     }
 
-    private static boolean isConfigured(Context context) {
-        try {
-            SingleAccountHelper.getCurrentSingleSignOnAccount(context);
-            return true;
-        } catch (NextcloudFilesAppAccountNotFoundException e) {
-            return false;
-        } catch (NoCurrentAccountSelectedException e) {
-            return false;
-        }
-    }
-
     /**
-     * Synchronization is only possible, if there is an active network connection and
-     * SingleSignOn is available
+     * Synchronization is only possible, if there is an active network connection.
+     *
+     * This method respects the user preference "Sync on Wi-Fi only".
+     *
      * NoteServerSyncHelper observes changes in the network connection.
      * The current state can be retrieved with this method.
      *
      * @return true if sync is possible, otherwise false.
      */
     public boolean isSyncPossible() {
-        return networkConnected && isConfigured(context.getApplicationContext());
+        return isSyncPossible;
+    }
+
+    public boolean isNetworkConnected() {
+        return networkConnected;
+    }
+
+    public boolean isSyncOnlyOnWifi() {
+        return syncOnlyOnWifi;
     }
 
     /**
@@ -185,8 +171,17 @@ public class NoteServerSyncHelper {
      *
      * @param callback Implementation of ISyncCallback, contains one method that shall be executed.
      */
-    public void addCallbackPush(ISyncCallback callback) {
-        callbacksPush.add(callback);
+    public void addCallbackPush(SingleSignOnAccount ssoAccount, ISyncCallback callback) {
+        if (ssoAccount == null) {
+            Log.i(TAG, "ssoAccount is null. Is this a local account?");
+            callback.onScheduled();
+            callback.onFinish();
+        } else {
+            if (!callbacksPush.containsKey(ssoAccount.name)) {
+                callbacksPush.put(ssoAccount.name, new ArrayList<>());
+            }
+            Objects.requireNonNull(callbacksPush.get(ssoAccount.name)).add(callback);
+        }
     }
 
     /**
@@ -197,8 +192,17 @@ public class NoteServerSyncHelper {
      *
      * @param callback Implementation of ISyncCallback, contains one method that shall be executed.
      */
-    public void addCallbackPull(ISyncCallback callback) {
-        callbacksPull.add(callback);
+    public void addCallbackPull(SingleSignOnAccount ssoAccount, ISyncCallback callback) {
+        if (ssoAccount == null) {
+            Log.i(TAG, "ssoAccount is null. Is this a local account?");
+            callback.onScheduled();
+            callback.onFinish();
+        } else {
+            if (!callbacksPull.containsKey(ssoAccount.name)) {
+                callbacksPull.put(ssoAccount.name, new ArrayList<>());
+            }
+            Objects.requireNonNull(callbacksPull.get(ssoAccount.name)).add(callback);
+        }
     }
 
 
@@ -208,28 +212,39 @@ public class NoteServerSyncHelper {
      *
      * @param onlyLocalChanges Whether to only push local changes to the server or to also load the whole list of notes from the server.
      */
-    public void scheduleSync(boolean onlyLocalChanges) {
-        Log.d(TAG, "Sync requested (" + (onlyLocalChanges ? "onlyLocalChanges" : "full") + "; " + (syncActive ? "sync active" : "sync NOT active") + ") ...");
-        if (isSyncPossible() && (!syncActive || onlyLocalChanges)) {
-            Log.d(TAG, "... starting now");
-            SyncTask syncTask = new SyncTask(onlyLocalChanges);
-            syncTask.addCallbacks(callbacksPush);
-            callbacksPush = new ArrayList<>();
-            if (!onlyLocalChanges) {
-                syncTask.addCallbacks(callbacksPull);
-                callbacksPull = new ArrayList<>();
-            }
-            syncTask.execute();
-        } else if (!onlyLocalChanges) {
-            Log.d(TAG, "... scheduled");
-            syncScheduled = true;
-            for (ISyncCallback callback : callbacksPush) {
-                callback.onScheduled();
-            }
+    public void scheduleSync(SingleSignOnAccount ssoAccount, boolean onlyLocalChanges) {
+        if (ssoAccount == null) {
+            Log.i(TAG, "ssoAccount is null. Is this a local account?");
         } else {
-            Log.d(TAG, "... do nothing");
-            for (ISyncCallback callback : callbacksPush) {
-                callback.onScheduled();
+            if (syncActive.get(ssoAccount.name) == null) {
+                syncActive.put(ssoAccount.name, false);
+            }
+            Log.d(TAG, "Sync requested (" + (onlyLocalChanges ? "onlyLocalChanges" : "full") + "; " + (syncActive.get(ssoAccount.name) ? "sync active" : "sync NOT active") + ") ...");
+            if (isSyncPossible() && (!syncActive.get(ssoAccount.name) || onlyLocalChanges)) {
+                Log.d(TAG, "... starting now");
+                SyncTask syncTask = new SyncTask(db.getLocalAccountByAccountName(ssoAccount.name), ssoAccount, onlyLocalChanges);
+                syncTask.addCallbacks(ssoAccount, callbacksPush.get(ssoAccount.name));
+                callbacksPush.put(ssoAccount.name, new ArrayList<>());
+                if (!onlyLocalChanges) {
+                    syncTask.addCallbacks(ssoAccount, callbacksPull.get(ssoAccount.name));
+                    callbacksPull.put(ssoAccount.name, new ArrayList<>());
+                }
+                syncTask.execute();
+            } else if (!onlyLocalChanges) {
+                Log.d(TAG, "... scheduled");
+                syncScheduled.put(ssoAccount.name, true);
+                if (callbacksPush.containsKey(ssoAccount.name) && callbacksPush.get(ssoAccount.name) != null) {
+                    for (ISyncCallback callback : callbacksPush.get(ssoAccount.name)) {
+                        callback.onScheduled();
+                    }
+                }
+            } else {
+                Log.d(TAG, "... do nothing");
+                if (callbacksPull.containsKey(ssoAccount.name) && callbacksPull.get(ssoAccount.name) != null) {
+                    for (ISyncCallback callback : callbacksPush.get(ssoAccount.name)) {
+                        callback.onScheduled();
+                    }
+                }
             }
         }
     }
@@ -239,18 +254,20 @@ public class NoteServerSyncHelper {
         NetworkInfo activeInfo = connMgr.getActiveNetworkInfo();
 
         if (activeInfo != null && activeInfo.isConnected()) {
-            networkConnected =
+            networkConnected = true;
+            isSyncPossible =
                     !syncOnlyOnWifi || ((ConnectivityManager) context.getApplicationContext()
                             .getSystemService(Context.CONNECTIVITY_SERVICE))
                             .getNetworkInfo(ConnectivityManager.TYPE_WIFI).isConnected();
 
-            if (networkConnected) {
+            if (isSyncPossible) {
                 Log.d(TAG, "Network connection established.");
             } else {
                 Log.d(TAG, "Network connected, but not used because only synced on wifi.");
             }
         } else {
             networkConnected = false;
+            isSyncPossible = false;
             Log.d(TAG, "No network connection.");
         }
     }
@@ -260,25 +277,32 @@ public class NoteServerSyncHelper {
      * Synchronization consists of two parts: pushLocalChanges and pullRemoteChanges.
      */
     private class SyncTask extends AsyncTask<Void, Void, LoginStatus> {
+        private final LocalAccount localAccount;
+        private final SingleSignOnAccount ssoAccount;
         private final boolean onlyLocalChanges;
-        private final List<ISyncCallback> callbacks = new ArrayList<>();
+        private final Map<String, List<ISyncCallback>> callbacks = new HashMap<>();
         private List<Throwable> exceptions = new ArrayList<>();
 
-        SyncTask(boolean onlyLocalChanges) {
+        SyncTask(@NonNull LocalAccount localAccount, @NonNull SingleSignOnAccount ssoAccount, boolean onlyLocalChanges) {
+            this.localAccount = localAccount;
+            this.ssoAccount = ssoAccount;
             this.onlyLocalChanges = onlyLocalChanges;
         }
 
-        void addCallbacks(List<ISyncCallback> callbacks) {
-            this.callbacks.addAll(callbacks);
+        void addCallbacks(SingleSignOnAccount ssoAccount, List<ISyncCallback> callbacks) {
+            this.callbacks.put(ssoAccount.name, callbacks);
         }
 
         @Override
         protected void onPreExecute() {
             super.onPreExecute();
-            if (!onlyLocalChanges && syncScheduled) {
-                syncScheduled = false;
+            if (!syncScheduled.containsKey(ssoAccount.name) || syncScheduled.get(ssoAccount.name) == null) {
+                syncScheduled.put(ssoAccount.name, false);
             }
-            syncActive = true;
+            if (!onlyLocalChanges && syncScheduled.get(ssoAccount.name)) {
+                syncScheduled.put(ssoAccount.name, false);
+            }
+            syncActive.put(ssoAccount.name, true);
         }
 
         @Override
@@ -314,20 +338,20 @@ public class NoteServerSyncHelper {
                             // if note is not new, try to edit it.
                             if (note.getRemoteId() > 0) {
                                 Log.v(TAG, "   ...try to edit");
-                                remoteNote = notesClient.editNote(note).getNote();
+                                remoteNote = notesClient.editNote(ssoAccount, note).getNote();
                             }
                             // However, the note may be deleted on the server meanwhile; or was never synchronized -> (re)create
                             // Please note, thas db.updateNote() realizes an optimistic conflict resolution, which is required for parallel changes of this Note from the UI.
                             if (remoteNote == null) {
                                 Log.v(TAG, "   ...Note does not exist on server -> (re)create");
-                                remoteNote = notesClient.createNote(note).getNote();
+                                remoteNote = notesClient.createNote(ssoAccount, note).getNote();
                             }
                             db.updateNote(note.getId(), remoteNote, note);
                             break;
                         case LOCAL_DELETED:
                             if (note.getRemoteId() > 0) {
                                 Log.v(TAG, "   ...delete (from server and local)");
-                                notesClient.deleteNote(note.getRemoteId());
+                                notesClient.deleteNote(ssoAccount, note.getRemoteId());
                             } else {
                                 Log.v(TAG, "   ...delete (only local, since it was not synchronized)");
                             }
@@ -360,7 +384,7 @@ public class NoteServerSyncHelper {
             LoginStatus status;
             try {
                 Map<Long, Long> idMap = db.getIdMap(localAccount.getId());
-                ServerResponse.NotesResponse response = notesClient.getNotes(localAccount.getModified(), localAccount.getEtag());
+                ServerResponse.NotesResponse response = notesClient.getNotes(ssoAccount, localAccount.getModified(), localAccount.getEtag());
                 List<CloudNote> remoteNotes = response.getNotes();
                 Set<Long> remoteIDs = new HashSet<>();
                 // pull remote changes: update or create each remote note
@@ -453,16 +477,18 @@ public class NoteServerSyncHelper {
                     }
                 }
             }
-            syncActive = false;
+            syncActive.put(ssoAccount.name, false);
             // notify callbacks
-            for (ISyncCallback callback : callbacks) {
-                callback.onFinish();
+            if (callbacks.containsKey(ssoAccount.name) && callbacks.get(ssoAccount.name) != null) {
+                for (ISyncCallback callback : callbacks.get(ssoAccount.name)) {
+                    callback.onFinish();
+                }
             }
             db.notifyNotesChanged();
             db.updateDynamicShortcuts(localAccount.getId());
             // start next sync if scheduled meanwhile
-            if (syncScheduled) {
-                scheduleSync(false);
+            if (syncScheduled.containsKey(ssoAccount.name) && syncScheduled.get(ssoAccount.name) != null && syncScheduled.get(ssoAccount.name)) {
+                scheduleSync(ssoAccount, false);
             }
         }
     }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesClient.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesClient.java
index 9c3fda3f..76d2f538 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesClient.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesClient.java
@@ -11,10 +11,7 @@ import com.nextcloud.android.sso.aidl.NextcloudRequest;
 import com.nextcloud.android.sso.api.AidlNetworkRequest;
 import com.nextcloud.android.sso.api.NextcloudAPI;
 import com.nextcloud.android.sso.api.Response;
-import com.nextcloud.android.sso.exceptions.NextcloudFilesAppAccountNotFoundException;
 import com.nextcloud.android.sso.exceptions.NextcloudFilesAppNotSupportedException;
-import com.nextcloud.android.sso.exceptions.NoCurrentAccountSelectedException;
-import com.nextcloud.android.sso.helper.SingleAccountHelper;
 import com.nextcloud.android.sso.model.SingleSignOnAccount;
 
 import org.json.JSONObject;
@@ -38,7 +35,7 @@ public class NotesClient {
     private static final String TAG = NotesClient.class.getSimpleName();
 
     private final Context appContext;
-    private NextcloudAPI mNextcloudAPI;
+    private static Map<String, NextcloudAPI> mNextcloudAPIs = new HashMap<>();
 
     /**
      * This entity class is used to return relevant data of the HTTP reponse.
@@ -48,7 +45,7 @@ public class NotesClient {
         private final String etag;
         private final long lastModified;
 
-        public ResponseData(String content, String etag, long lastModified) {
+        ResponseData(String content, String etag, long lastModified) {
             this.content = content;
             this.etag = etag;
             this.lastModified = lastModified;
@@ -93,45 +90,21 @@ public class NotesClient {
 
     NotesClient(Context appContext) {
         this.appContext = appContext;
-        updateAccount();
     }
 
-    void updateAccount() {
-        if (mNextcloudAPI != null) {
-            mNextcloudAPI.stop();
-        }
-        try {
-            SingleSignOnAccount ssoAccount = SingleAccountHelper.getCurrentSingleSignOnAccount(appContext);
-            Log.v(TAG, "NextcloudRequest account: " + ssoAccount.name);
-            mNextcloudAPI = new NextcloudAPI(appContext, ssoAccount, new GsonBuilder().create(), new NextcloudAPI.ApiConnectedListener() {
-                @Override
-                public void onConnected() {
-                    Log.v(TAG, "SSO API connected");
-                }
-
-                @Override
-                public void onError(Exception ex) {
-                    ex.printStackTrace();
-                }
-            });
-        } catch (NextcloudFilesAppAccountNotFoundException | NoCurrentAccountSelectedException e) {
-            e.printStackTrace();
-        }
-    }
-
-    NotesResponse getNotes(long lastModified, String lastETag) throws Exception {
+    NotesResponse getNotes(SingleSignOnAccount ssoAccount, long lastModified, String lastETag) throws Exception {
         Map<String, String> parameter = new HashMap<>();
         parameter.put(GET_PARAM_KEY_PRUNE_BEFORE, Long.toString(lastModified));
-        return new NotesResponse(requestServer("notes", METHOD_GET, parameter, null, lastETag));
+        return new NotesResponse(requestServer(ssoAccount, "notes", METHOD_GET, parameter, null, lastETag));
     }
 
-    private NoteResponse putNote(CloudNote note, String path, String method) throws Exception {
+    private NoteResponse putNote(SingleSignOnAccount ssoAccount, CloudNote note, String path, String method) throws Exception {
         JSONObject paramObject = new JSONObject();
         paramObject.accumulate(JSON_CONTENT, note.getContent());
         paramObject.accumulate(JSON_MODIFIED, note.getModified().getTimeInMillis() / 1000);
         paramObject.accumulate(JSON_FAVORITE, note.isFavorite());
         paramObject.accumulate(JSON_CATEGORY, note.getCategory());
-        return new NoteResponse(requestServer(path, method, null, paramObject, null));
+        return new NoteResponse(requestServer(ssoAccount, path, method, null, paramObject, null));
     }
 
     /**
@@ -141,17 +114,17 @@ public class NotesClient {
      * @return Created Note including generated Title, ID and lastModified-Date
      * @throws Exception
      */
-    NoteResponse createNote(CloudNote note) throws Exception {
-        return putNote(note, "notes", METHOD_POST);
+    NoteResponse createNote(SingleSignOnAccount ssoAccount, CloudNote note) throws Exception {
+        return putNote(ssoAccount, note, "notes", METHOD_POST);
     }
 
-    NoteResponse editNote(CloudNote note) throws Exception {
-        return putNote(note, "notes/" + note.getRemoteId(), METHOD_PUT);
+    NoteResponse editNote(SingleSignOnAccount ssoAccount, CloudNote note) throws Exception {
+        return putNote(ssoAccount, note, "notes/" + note.getRemoteId(), METHOD_PUT);
     }
 
-    void deleteNote(long noteId) {
+    void deleteNote(SingleSignOnAccount ssoAccount, long noteId) {
         try {
-            this.requestServer("notes/" + noteId, METHOD_DELETE, null, null, null);
+            this.requestServer(ssoAccount, "notes/" + noteId, METHOD_DELETE, null, null, null);
         } catch (Exception e) {
             e.printStackTrace();
         }
@@ -167,7 +140,7 @@ public class NotesClient {
      * @param lastETag    optional ETag of last response
      * @return Body of answer
      */
-    private ResponseData requestServer(String target, String method, Map<String, String> parameter, JSONObject requestBody, String lastETag) throws Exception {
+    private ResponseData requestServer(SingleSignOnAccount ssoAccount, String target, String method, Map<String, String> parameter, JSONObject requestBody, String lastETag) throws Exception {
         NextcloudRequest.Builder requestBuilder = new NextcloudRequest.Builder()
                 .setMethod(method)
                 .setUrl(API_PATH + target);
@@ -189,9 +162,9 @@ public class NotesClient {
 
         StringBuilder result = new StringBuilder();
 
-        Log.v(TAG, "NextcloudRequest: " + nextcloudRequest.toString());
         try {
-            Response response = mNextcloudAPI.performNetworkRequestV2(nextcloudRequest);
+            Log.v(TAG, ssoAccount.name + " => " + nextcloudRequest.getMethod() + " " + nextcloudRequest.getUrl() +  " ");
+            Response response = getNextcloudAPI(appContext, ssoAccount).performNetworkRequestV2(nextcloudRequest);
             Log.v(TAG, "NextcloudRequest: " + nextcloudRequest.toString());
             BufferedReader rd = new BufferedReader(new InputStreamReader(response.getBody()));
             String line;
@@ -223,4 +196,25 @@ public class NotesClient {
             }
         }
     }
+
+    private static NextcloudAPI getNextcloudAPI(Context appContext, SingleSignOnAccount ssoAccount) {
+        if (mNextcloudAPIs.containsKey(ssoAccount.name)) {
+            return mNextcloudAPIs.get(ssoAccount.name);
+        } else {
+            Log.v(TAG, "NextcloudRequest account: " + ssoAccount.name);
+            NextcloudAPI nextcloudAPI = new NextcloudAPI(appContext, ssoAccount, new GsonBuilder().create(), new NextcloudAPI.ApiConnectedListener() {
+                @Override
+                public void onConnected() {
+                    Log.v(TAG, "SSO API connected for " + ssoAccount);
+                }
+
+                @Override
+                public void onError(Exception ex) {
+                    ex.printStackTrace();
+                }
+            });
+            mNextcloudAPIs.put(ssoAccount.name, nextcloudAPI);
+            return nextcloudAPI;
+        }
+    }
 }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/SyncWorker.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/SyncWorker.java
new file mode 100644
index 00000000..05daacef
--- /dev/null
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/SyncWorker.java
@@ -0,0 +1,78 @@
+package it.niedermann.owncloud.notes.persistence;
+
+import android.content.Context;
+import android.util.Log;
+
+import androidx.annotation.NonNull;
+import androidx.work.Constraints;
+import androidx.work.ExistingPeriodicWorkPolicy;
+import androidx.work.NetworkType;
+import androidx.work.PeriodicWorkRequest;
+import androidx.work.WorkManager;
+import androidx.work.Worker;
+import androidx.work.WorkerParameters;
+
+import com.nextcloud.android.sso.AccountImporter;
+import com.nextcloud.android.sso.exceptions.NextcloudFilesAppAccountNotFoundException;
+import com.nextcloud.android.sso.model.SingleSignOnAccount;
+
+import java.util.concurrent.TimeUnit;
+
+import it.niedermann.owncloud.notes.R;
+import it.niedermann.owncloud.notes.model.LocalAccount;
+
+public class SyncWorker extends Worker {
+
+    private static final String TAG = SyncWorker.class.getCanonicalName();
+    private static final String WORKER_TAG = "background_synchronization";
+
+    private static final Constraints constraints = new Constraints.Builder()
+            .setRequiredNetworkType(NetworkType.CONNECTED)
+            .build();
+
+    public SyncWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
+        super(context, workerParams);
+    }
+
+    @NonNull
+    @Override
+    public Result doWork() {
+        NoteSQLiteOpenHelper db = NoteSQLiteOpenHelper.getInstance(getApplicationContext());
+        for (LocalAccount account : db.getAccounts()) {
+            try {
+                SingleSignOnAccount ssoAccount = AccountImporter.getSingleSignOnAccount(getApplicationContext(), account.getAccountName());
+                Log.v(TAG, "Starting background synchronization for " + ssoAccount.name);
+                db.getNoteServerSyncHelper().addCallbackPull(ssoAccount, () -> Log.v(TAG, "Finished background synchronization for " + ssoAccount.name));
+                db.getNoteServerSyncHelper().scheduleSync(ssoAccount, false);
+            } catch (NextcloudFilesAppAccountNotFoundException e) {
+                e.printStackTrace();
+            }
+        }
+        // TODO return result depending on callbackPull
+        return Result.success();
+    }
+
+    public static void update(@NonNull Context context, @NonNull String preferenceValue) {
+        deregister(context);
+        if (!context.getString(R.string.pref_value_sync_off).equals(preferenceValue)) {
+            int repeatInterval = 15;
+            TimeUnit unit = TimeUnit.MINUTES;
+            if (context.getString(R.string.pref_value_sync_1_hour).equals(preferenceValue)) {
+                repeatInterval = 1;
+                unit = TimeUnit.HOURS;
+            } else if (context.getString(R.string.pref_value_sync_6_hours).equals(preferenceValue)) {
+                repeatInterval = 6;
+                unit = TimeUnit.HOURS;
+            }
+            PeriodicWorkRequest work = new PeriodicWorkRequest.Builder(SyncWorker.class, repeatInterval, unit)
+                    .setConstraints(constraints).build();
+            WorkManager.getInstance(context.getApplicationContext()).enqueueUniquePeriodicWork(TAG, ExistingPeriodicWorkPolicy.REPLACE, work);
+            Log.v(TAG, "Registering worker running each " + repeatInterval + " " + unit);
+        }
+    }
+
+    private static void deregister(@NonNull Context context) {
+        Log.v(TAG, "Deregistering all workers with tag \"" + WORKER_TAG + "\"");
+        WorkManager.getInstance(context.getApplicationContext()).cancelAllWorkByTag(WORKER_TAG);
+    }
+}
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/util/SSOUtil.java b/app/src/main/java/it/niedermann/owncloud/notes/util/SSOUtil.java
index 6759d223..5089f14d 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/util/SSOUtil.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/util/SSOUtil.java
@@ -1,13 +1,17 @@
 package it.niedermann.owncloud.notes.util;
 
 import android.app.Activity;
+import android.content.Context;
 import android.util.Log;
 
 import androidx.annotation.NonNull;
 
 import com.nextcloud.android.sso.AccountImporter;
 import com.nextcloud.android.sso.exceptions.AndroidGetAccountsPermissionNotGranted;
+import com.nextcloud.android.sso.exceptions.NextcloudFilesAppAccountNotFoundException;
 import com.nextcloud.android.sso.exceptions.NextcloudFilesAppNotInstalledException;
+import com.nextcloud.android.sso.exceptions.NoCurrentAccountSelectedException;
+import com.nextcloud.android.sso.helper.SingleAccountHelper;
 import com.nextcloud.android.sso.ui.UiExceptionManager;
 
 public class SSOUtil {
@@ -36,4 +40,15 @@ public class SSOUtil {
             AccountImporter.requestAndroidAccountPermissionsAndPickAccount(activity);
         }
     }
+
+    public static boolean isConfigured(Context context) {
+        try {
+            SingleAccountHelper.getCurrentSingleSignOnAccount(context);
+            return true;
+        } catch (NextcloudFilesAppAccountNotFoundException e) {
+            return false;
+        } catch (NoCurrentAccountSelectedException e) {
+            return false;
+        }
+    }
 }
diff --git a/app/src/main/res/drawable/ic_network_wifi_grey600_24dp.xml b/app/src/main/res/drawable/ic_network_wifi_grey600_24dp.xml
new file mode 100644
index 00000000..1c3b9a41
--- /dev/null
+++ b/app/src/main/res/drawable/ic_network_wifi_grey600_24dp.xml
@@ -0,0 +1,6 @@
+<vector android:autoMirrored="true" android:height="24dp"
+    android:tint="#757575" android:viewportHeight="24.0"
+    android:viewportWidth="24.0" android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
+    <path android:fillAlpha=".3" android:fillColor="#FF000000" android:pathData="M12.01,21.49L23.64,7c-0.45,-0.34 -4.93,-4 -11.64,-4C5.28,3 0.81,6.66 0.36,7l11.63,14.49 0.01,0.01 0.01,-0.01z"/>
+    <path android:fillColor="#FF000000" android:pathData="M3.53,10.95l8.46,10.54 0.01,0.01 0.01,-0.01 8.46,-10.54C20.04,10.62 16.81,8 12,8c-4.81,0 -8.04,2.62 -8.47,2.95z"/>
+</vector>
diff --git a/app/src/main/res/layout/item_notes_list_note_item.xml b/app/src/main/res/layout/item_notes_list_note_item.xml
index 19ba07b4..2c6a0eed 100644
--- a/app/src/main/res/layout/item_notes_list_note_item.xml
+++ b/app/src/main/res/layout/item_notes_list_note_item.xml
@@ -79,7 +79,8 @@
                     android:id="@+id/noteTitle"
                     android:layout_width="wrap_content"
                     android:layout_height="wrap_content"
-                    android:singleLine="true"
+                    android:ellipsize="end"
+                    android:maxLines="1"
                     android:layout_weight="1"
                     android:textSize="@dimen/primary_font_size"
                     android:textColor="?android:textColorPrimary"
diff --git a/app/src/main/res/values-sl/strings.xml b/app/src/main/res/values-sl/strings.xml
index f5011dc4..c0899102 100644
--- a/app/src/main/res/values-sl/strings.xml
+++ b/app/src/main/res/values-sl/strings.xml
@@ -119,6 +119,7 @@
     <string name="bulk_notes_deleted">Izbrisane %1$d zabeležke</string>
     <string name="bulk_notes_restored">Obnovljene %1$d zabeležke</string>
     <string name="category_readonly">Le za branje</string>
+    <string name="no_category">Brez kategorije</string>
     <string name="add_category">Dodaj %1$s</string>
 
     <!-- Array: note modes -->
diff --git a/app/src/main/res/values-sr/strings.xml b/app/src/main/res/values-sr/strings.xml
index 50060128..ae276031 100644
--- a/app/src/main/res/values-sr/strings.xml
+++ b/app/src/main/res/values-sr/strings.xml
@@ -16,6 +16,8 @@
     <string name="simple_bold">Подебљано</string>
     <string name="simple_link">Веза</string>
     <string name="simple_italic">Курзив</string>
+    <string name="action_note_deleted">Обрисано %1$s</string>
+    <string name="action_note_restored">Повраћено %1$s</string>
     <string name="action_undo">Опозови</string>
     <string name="action_drawer_open">отвори навигацију</string>
     <string name="action_drawer_close">затвори навигацију</string>
@@ -50,6 +52,7 @@
     <string name="error_sync">Синхронизација није успела%1$s</string>
     <string name="error_json">Да ли је апликација Белешки активирана на серверу?</string>
     <string name="error_no_network">нема мрежне везе</string>
+    <string name="error_files_app">да ли имате инсталирану апликацију за фајлове?</string>
     <string name="error_unknown">Десила се непозната грешка</string>
 
     <!-- About -->
@@ -108,9 +111,15 @@
     <string name="account_already_imported">Налог је већ увезен</string>
     <string name="no_notes_yet">Још нема белешки</string>
     <string name="no_notes_yet_description">Притисните + дугме да направите нову белешку</string>
+    <string name="could_not_load_preview_two_digit_numbered_list">Не могу да учитам преглед. Проверите да ли постоји двоцифрена ставка у листи без садржаја.</string>
     <string name="simple_more">Још</string>
     <string name="simple_move">Помери</string>
+    <string name="error_files_app_version_too_old">Да ли је Ваша апликација за фајлове на најновијој верзији?</string>
+    <string name="checkbox_could_not_be_toggled">Поље за потврду не може да се укључи/искључи.</string>
+    <string name="bulk_notes_deleted">Обрисано %1$d белешки</string>
+    <string name="bulk_notes_restored">Повраћено %1$d белешки</string>
     <string name="category_readonly">Само за читање</string>
+    <string name="no_category">Нема категорије</string>
     <string name="add_category">Додај %1$s</string>
 
     <!-- Array: note modes -->
diff --git a/app/src/main/res/values/arrays.xml b/app/src/main/res/values/arrays.xml
index 1d4ed668..cc342086 100644
--- a/app/src/main/res/values/arrays.xml
+++ b/app/src/main/res/values/arrays.xml
@@ -10,4 +10,10 @@
         <item>@string/pref_value_font_size_medium</item>
         <item>@string/pref_value_font_size_large</item>
     </string-array>
+    <string-array name="sync_values">
+        <item>@string/pref_value_sync_off</item>
+        <item>@string/pref_value_sync_15_minutes</item>
+        <item>@string/pref_value_sync_1_hour</item>
+        <item>@string/pref_value_sync_6_hours</item>
+    </string-array>
 </resources>
\ No newline at end of file
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 3b5ff041..8b353149 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -44,6 +44,7 @@
     <string name="settings_font_size">Font size</string>
     <string name="settings_wifi_only">Sync only on Wi-Fi</string>
     <string name="settings_lock">Password protection</string>
+    <string name="settings_background_sync">Background synchronization</string>
 
     <!-- Certificates -->
 
@@ -114,16 +115,23 @@
     <string name="pref_key_wifi_only" translatable="false">wifiOnly</string>
     <string name="pref_key_lock" translatable="false">lock</string>
     <string name="pref_key_last_note_mode" translatable="false">lastNoteMode</string>
+    <string name="pref_key_background_sync" translatable="false">backgroundSync</string>
     <string name="pref_value_mode_edit" translatable="false">edit</string>
     <string name="pref_value_mode_preview" translatable="false">preview</string>
     <string name="pref_value_mode_last" translatable="false">last</string>
     <string name="pref_value_font_size_small" translatable="false">small</string>
     <string name="pref_value_font_size_medium" translatable="false">medium</string>
     <string name="pref_value_font_size_large" translatable="false">large</string>
+    <string name="pref_value_sync_off" translatable="false">off</string>
+    <string name="pref_value_sync_15_minutes" translatable="false">15_minutes</string>
+    <string name="pref_value_sync_1_hour" translatable="false">1_hour</string>
+    <string name="pref_value_sync_6_hours" translatable="false">6_hours</string>
+    <!-- These values should not be translateable. They should be migrated at some point.  -->
     <string name="pref_value_theme_light">Light</string>
     <string name="pref_value_font_normal">Normal</string>
     <string name="pref_value_wifi_and_mobile">Sync on Wi-Fi and mobile data</string>
     <string name="pref_value_lock">Password protection</string>
+
     <string name="simple_error">Error</string>
     <string name="simple_close">Close</string>
     <string name="simple_copy">Copy</string>
@@ -166,6 +174,14 @@
         <item>Large</item>
     </string-array>
 
+    <!-- Array: background synchronization -->
+    <string-array name="sync_entries">
+        <item>Off</item>
+        <item>15 minutes</item>
+        <item>1 hour</item>
+        <item>6 hours</item>
+    </string-array>
+
     <!-- Plurals -->
     <plurals name="ab_selected">
         <item quantity="one">%d selected</item>
diff --git a/app/src/main/res/xml/preferences.xml b/app/src/main/res/xml/preferences.xml
index 3b3c4ead..9219480f 100644
--- a/app/src/main/res/xml/preferences.xml
+++ b/app/src/main/res/xml/preferences.xml
@@ -45,9 +45,19 @@
 
     <SwitchPreference
         android:defaultValue="@string/pref_value_wifi_and_mobile"
-        android:icon="@drawable/ic_sync_black_24dp"
+        android:icon="@drawable/ic_network_wifi_grey600_24dp"
         android:key="@string/pref_key_wifi_only"
         android:layout="@layout/item_pref"
         android:title="@string/settings_wifi_only" />
 
+    <ListPreference
+        android:defaultValue="@string/pref_value_sync_off"
+        android:entries="@array/sync_entries"
+        android:entryValues="@array/sync_values"
+        android:icon="@drawable/ic_sync_black_24dp"
+        android:key="@string/pref_key_background_sync"
+        android:layout="@layout/item_pref"
+        android:summary="%s"
+        android:title="@string/settings_background_sync" />
+
 </PreferenceScreen>