diff --git a/app/src/main/java/org/tasks/activities/CreateListViewModel.java b/app/src/main/java/org/tasks/activities/CreateListViewModel.java
deleted file mode 100644
index 6d9c34a81..000000000
--- a/app/src/main/java/org/tasks/activities/CreateListViewModel.java
+++ /dev/null
@@ -1,12 +0,0 @@
-package org.tasks.activities;
-
-import com.google.api.services.tasks.model.TaskList;
-import com.todoroo.astrid.gtasks.api.GtasksInvoker;
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class CreateListViewModel extends CompletableViewModel<TaskList> {
-  void createList(GtasksInvoker invoker, String account, String name) {
-    run(() -> invoker.forAccount(account).createGtaskList(name));
-  }
-}
diff --git a/app/src/main/java/org/tasks/activities/CreateListViewModel.kt b/app/src/main/java/org/tasks/activities/CreateListViewModel.kt
new file mode 100644
index 000000000..54278421d
--- /dev/null
+++ b/app/src/main/java/org/tasks/activities/CreateListViewModel.kt
@@ -0,0 +1,11 @@
+package org.tasks.activities
+
+import com.google.api.services.tasks.model.TaskList
+import com.todoroo.astrid.gtasks.api.GtasksInvoker
+import org.tasks.ui.CompletableViewModel
+
+class CreateListViewModel : CompletableViewModel<TaskList?>() {
+    fun createList(invoker: GtasksInvoker, account: String?, name: String?) {
+        run { invoker.forAccount(account!!).createGtaskList(name) }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/activities/GoogleTaskListSettingsActivity.java b/app/src/main/java/org/tasks/activities/GoogleTaskListSettingsActivity.java
index 3bcc1704f..ab5407695 100644
--- a/app/src/main/java/org/tasks/activities/GoogleTaskListSettingsActivity.java
+++ b/app/src/main/java/org/tasks/activities/GoogleTaskListSettingsActivity.java
@@ -22,6 +22,7 @@ import com.todoroo.astrid.service.TaskDeleter;
 import dagger.hilt.android.AndroidEntryPoint;
 import dagger.hilt.android.qualifiers.ApplicationContext;
 import javax.inject.Inject;
+import kotlin.Unit;
 import org.tasks.R;
 import org.tasks.data.GoogleTaskAccount;
 import org.tasks.data.GoogleTaskList;
@@ -206,7 +207,7 @@ public class GoogleTaskListSettingsActivity extends BaseListSettingsActivity {
     return !getNewName().equals(gtasksList.getTitle());
   }
 
-  private void onListCreated(TaskList taskList) {
+  private Unit onListCreated(TaskList taskList) {
     gtasksList.setRemoteId(taskList.getId());
     gtasksList.setTitle(taskList.getTitle());
     gtasksList.setColor(selectedColor);
@@ -215,6 +216,7 @@ public class GoogleTaskListSettingsActivity extends BaseListSettingsActivity {
     setResult(
         RESULT_OK, new Intent().putExtra(MainActivity.OPEN_FILTER, new GtasksFilter(gtasksList)));
     finish();
+    return Unit.INSTANCE;
   }
 
   private void onListDeleted(boolean deleted) {
@@ -225,7 +227,7 @@ public class GoogleTaskListSettingsActivity extends BaseListSettingsActivity {
     }
   }
 
-  private void onListRenamed(TaskList taskList) {
+  private Unit onListRenamed(TaskList taskList) {
     gtasksList.setTitle(taskList.getTitle());
     gtasksList.setColor(selectedColor);
     gtasksList.setIcon(selectedIcon);
@@ -235,11 +237,13 @@ public class GoogleTaskListSettingsActivity extends BaseListSettingsActivity {
         new Intent(TaskListFragment.ACTION_RELOAD)
             .putExtra(MainActivity.OPEN_FILTER, new GtasksFilter(gtasksList)));
     finish();
+    return Unit.INSTANCE;
   }
 
-  private void requestFailed(Throwable error) {
+  private Unit requestFailed(Throwable error) {
     Timber.e(error);
     hideProgressIndicator();
     Toast.makeText(this, R.string.gtasks_GLA_errorIOAuth, Toast.LENGTH_LONG).show();
+    return Unit.INSTANCE;
   }
 }
diff --git a/app/src/main/java/org/tasks/activities/RenameListViewModel.java b/app/src/main/java/org/tasks/activities/RenameListViewModel.java
deleted file mode 100644
index 4f741eb17..000000000
--- a/app/src/main/java/org/tasks/activities/RenameListViewModel.java
+++ /dev/null
@@ -1,13 +0,0 @@
-package org.tasks.activities;
-
-import com.google.api.services.tasks.model.TaskList;
-import com.todoroo.astrid.gtasks.api.GtasksInvoker;
-import org.tasks.data.GoogleTaskList;
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class RenameListViewModel extends CompletableViewModel<TaskList> {
-  void renameList(GtasksInvoker invoker, GoogleTaskList list, String name) {
-    run(() -> invoker.forAccount(list.getAccount()).renameGtaskList(list.getRemoteId(), name));
-  }
-}
diff --git a/app/src/main/java/org/tasks/activities/RenameListViewModel.kt b/app/src/main/java/org/tasks/activities/RenameListViewModel.kt
new file mode 100644
index 000000000..120e37350
--- /dev/null
+++ b/app/src/main/java/org/tasks/activities/RenameListViewModel.kt
@@ -0,0 +1,12 @@
+package org.tasks.activities
+
+import com.google.api.services.tasks.model.TaskList
+import com.todoroo.astrid.gtasks.api.GtasksInvoker
+import org.tasks.data.GoogleTaskList
+import org.tasks.ui.CompletableViewModel
+
+class RenameListViewModel : CompletableViewModel<TaskList?>() {
+    fun renameList(invoker: GtasksInvoker, list: GoogleTaskList, name: String?) {
+        run { invoker.forAccount(list.account!!).renameGtaskList(list.remoteId, name) }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/caldav/AddCaldavAccountViewModel.java b/app/src/main/java/org/tasks/caldav/AddCaldavAccountViewModel.java
deleted file mode 100644
index 1f821b62c..000000000
--- a/app/src/main/java/org/tasks/caldav/AddCaldavAccountViewModel.java
+++ /dev/null
@@ -1,11 +0,0 @@
-package org.tasks.caldav;
-
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class AddCaldavAccountViewModel extends CompletableViewModel<String> {
-  void addAccount(CaldavClient client, String url, String username, String password) {
-    run(
-        () -> client.setForeground().forUrl(url, username, password).getHomeSet());
-  }
-}
diff --git a/app/src/main/java/org/tasks/caldav/AddCaldavAccountViewModel.kt b/app/src/main/java/org/tasks/caldav/AddCaldavAccountViewModel.kt
new file mode 100644
index 000000000..e29d7a594
--- /dev/null
+++ b/app/src/main/java/org/tasks/caldav/AddCaldavAccountViewModel.kt
@@ -0,0 +1,9 @@
+package org.tasks.caldav
+
+import org.tasks.ui.CompletableViewModel
+
+class AddCaldavAccountViewModel : CompletableViewModel<String>() {
+    fun addAccount(client: CaldavClient, url: String?, username: String?, password: String?) {
+        run { client.setForeground().forUrl(url, username, password).homeSet }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/caldav/BaseCaldavCalendarSettingsActivity.java b/app/src/main/java/org/tasks/caldav/BaseCaldavCalendarSettingsActivity.java
index 5cd68a83c..01bf39144 100644
--- a/app/src/main/java/org/tasks/caldav/BaseCaldavCalendarSettingsActivity.java
+++ b/app/src/main/java/org/tasks/caldav/BaseCaldavCalendarSettingsActivity.java
@@ -22,6 +22,7 @@ import com.todoroo.astrid.helper.UUIDHelper;
 import com.todoroo.astrid.service.TaskDeleter;
 import java.net.ConnectException;
 import javax.inject.Inject;
+import kotlin.Unit;
 import org.tasks.R;
 import org.tasks.activities.BaseListSettingsActivity;
 import org.tasks.data.CaldavAccount;
@@ -152,7 +153,7 @@ public abstract class BaseCaldavCalendarSettingsActivity extends BaseListSetting
     return progressView.getVisibility() == View.VISIBLE;
   }
 
-  protected void requestFailed(Throwable t) {
+  protected Unit requestFailed(Throwable t) {
     hideProgressIndicator();
 
     if (t instanceof HttpException) {
@@ -164,6 +165,7 @@ public abstract class BaseCaldavCalendarSettingsActivity extends BaseListSetting
     } else {
       showSnackbar(R.string.error_adding_account, t.getMessage());
     }
+    return Unit.INSTANCE;
   }
 
   private void showSnackbar(int resId, Object... formatArgs) {
@@ -181,7 +183,7 @@ public abstract class BaseCaldavCalendarSettingsActivity extends BaseListSetting
     snackbar.show();
   }
 
-  protected void createSuccessful(String url) {
+  protected Unit createSuccessful(String url) {
     CaldavCalendar caldavCalendar = new CaldavCalendar();
     caldavCalendar.setUuid(UUIDHelper.newUUID());
     caldavCalendar.setAccount(caldavAccount.getUuid());
@@ -194,9 +196,10 @@ public abstract class BaseCaldavCalendarSettingsActivity extends BaseListSetting
         RESULT_OK,
         new Intent().putExtra(MainActivity.OPEN_FILTER, new CaldavFilter(caldavCalendar)));
     finish();
+    return Unit.INSTANCE;
   }
 
-  protected void updateCalendar() {
+  protected Unit updateCalendar() {
     caldavCalendar.setName(getNewName());
     caldavCalendar.setColor(selectedColor);
     caldavCalendar.setIcon(selectedIcon);
@@ -206,6 +209,7 @@ public abstract class BaseCaldavCalendarSettingsActivity extends BaseListSetting
         new Intent(TaskListFragment.ACTION_RELOAD)
             .putExtra(MainActivity.OPEN_FILTER, new CaldavFilter(caldavCalendar)));
     finish();
+    return Unit.INSTANCE;
   }
 
   @Override
diff --git a/app/src/main/java/org/tasks/caldav/CaldavAccountSettingsActivity.kt b/app/src/main/java/org/tasks/caldav/CaldavAccountSettingsActivity.kt
index c865e64a7..792686820 100644
--- a/app/src/main/java/org/tasks/caldav/CaldavAccountSettingsActivity.kt
+++ b/app/src/main/java/org/tasks/caldav/CaldavAccountSettingsActivity.kt
@@ -2,9 +2,8 @@ package org.tasks.caldav
 
 import android.app.Activity
 import android.os.Bundle
+import androidx.activity.viewModels
 import androidx.appcompat.widget.Toolbar
-import androidx.lifecycle.Observer
-import androidx.lifecycle.ViewModelProvider
 import com.todoroo.astrid.helper.UUIDHelper
 import dagger.hilt.android.AndroidEntryPoint
 import org.tasks.R
@@ -16,16 +15,13 @@ import javax.inject.Inject
 class CaldavAccountSettingsActivity : BaseCaldavAccountSettingsActivity(), Toolbar.OnMenuItemClickListener {
     @Inject lateinit var client: CaldavClient
 
-    private var addCaldavAccountViewModel: AddCaldavAccountViewModel? = null
-    private var updateCaldavAccountViewModel: UpdateCaldavAccountViewModel? = null
+    private val addCaldavAccountViewModel: AddCaldavAccountViewModel by viewModels()
+    private val updateCaldavAccountViewModel: UpdateCaldavAccountViewModel by viewModels()
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        val provider = ViewModelProvider(this)
-        addCaldavAccountViewModel = provider.get(AddCaldavAccountViewModel::class.java)
-        updateCaldavAccountViewModel = provider.get(UpdateCaldavAccountViewModel::class.java)
-        addCaldavAccountViewModel!!.observe(this, Observer { principal: String -> this.addAccount(principal) }, Observer { t: Throwable? -> requestFailed(t!!) })
-        updateCaldavAccountViewModel!!.observe(this, Observer { principal: String? -> this.updateAccount(principal) }, Observer { t: Throwable? -> requestFailed(t!!) })
+        addCaldavAccountViewModel.observe(this, { addAccount(it) }, { requestFailed(it) })
+        updateCaldavAccountViewModel.observe(this, { updateAccount(it) }, { requestFailed(it) })
     }
 
     override val description: Int
@@ -61,11 +57,11 @@ class CaldavAccountSettingsActivity : BaseCaldavAccountSettingsActivity(), Toolb
     }
 
     override fun addAccount(url: String?, username: String?, password: String?) {
-        addCaldavAccountViewModel!!.addAccount(client, url, username, password)
+        addCaldavAccountViewModel.addAccount(client, url, username, password)
     }
 
     override fun updateAccount(url: String?, username: String?, password: String?) {
-        updateCaldavAccountViewModel!!.updateCaldavAccount(client, url, username, password)
+        updateCaldavAccountViewModel.updateCaldavAccount(client, url, username, password)
     }
 
     override fun updateAccount() {
diff --git a/app/src/main/java/org/tasks/caldav/CreateCalendarViewModel.java b/app/src/main/java/org/tasks/caldav/CreateCalendarViewModel.java
deleted file mode 100644
index 71e4748ef..000000000
--- a/app/src/main/java/org/tasks/caldav/CreateCalendarViewModel.java
+++ /dev/null
@@ -1,11 +0,0 @@
-package org.tasks.caldav;
-
-import org.tasks.data.CaldavAccount;
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class CreateCalendarViewModel extends CompletableViewModel<String> {
-  void createCalendar(CaldavClient client, CaldavAccount account, String name, int color) {
-    run(() -> client.forAccount(account).makeCollection(name, color));
-  }
-}
diff --git a/app/src/main/java/org/tasks/caldav/CreateCalendarViewModel.kt b/app/src/main/java/org/tasks/caldav/CreateCalendarViewModel.kt
new file mode 100644
index 000000000..a41f8cf1f
--- /dev/null
+++ b/app/src/main/java/org/tasks/caldav/CreateCalendarViewModel.kt
@@ -0,0 +1,10 @@
+package org.tasks.caldav
+
+import org.tasks.data.CaldavAccount
+import org.tasks.ui.CompletableViewModel
+
+class CreateCalendarViewModel : CompletableViewModel<String?>() {
+    fun createCalendar(client: CaldavClient, account: CaldavAccount?, name: String?, color: Int) {
+        run { client.forAccount(account).makeCollection(name, color) }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/caldav/UpdateCaldavAccountViewModel.java b/app/src/main/java/org/tasks/caldav/UpdateCaldavAccountViewModel.java
deleted file mode 100644
index a25416b84..000000000
--- a/app/src/main/java/org/tasks/caldav/UpdateCaldavAccountViewModel.java
+++ /dev/null
@@ -1,11 +0,0 @@
-package org.tasks.caldav;
-
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class UpdateCaldavAccountViewModel extends CompletableViewModel<String> {
-  void updateCaldavAccount(
-      CaldavClient client, String url, String username, String password) {
-    run(() -> client.forUrl(url, username, password).getHomeSet());
-  }
-}
diff --git a/app/src/main/java/org/tasks/caldav/UpdateCaldavAccountViewModel.kt b/app/src/main/java/org/tasks/caldav/UpdateCaldavAccountViewModel.kt
new file mode 100644
index 000000000..b42c55904
--- /dev/null
+++ b/app/src/main/java/org/tasks/caldav/UpdateCaldavAccountViewModel.kt
@@ -0,0 +1,12 @@
+package org.tasks.caldav
+
+import org.tasks.ui.CompletableViewModel
+
+class UpdateCaldavAccountViewModel : CompletableViewModel<String>() {
+    fun updateCaldavAccount(
+            client: CaldavClient, url: String?, username: String?, password: String?) {
+        run {
+            client.forUrl(url, username, password).homeSet
+        }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/caldav/UpdateCalendarViewModel.java b/app/src/main/java/org/tasks/caldav/UpdateCalendarViewModel.java
deleted file mode 100644
index 32764a84d..000000000
--- a/app/src/main/java/org/tasks/caldav/UpdateCalendarViewModel.java
+++ /dev/null
@@ -1,13 +0,0 @@
-package org.tasks.caldav;
-
-import org.tasks.data.CaldavAccount;
-import org.tasks.data.CaldavCalendar;
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class UpdateCalendarViewModel extends CompletableViewModel<String> {
-  void updateCalendar(
-      CaldavClient client, CaldavAccount account, CaldavCalendar calendar, String name, int color) {
-    run(() -> client.forCalendar(account, calendar).updateCollection(name, color));
-  }
-}
diff --git a/app/src/main/java/org/tasks/caldav/UpdateCalendarViewModel.kt b/app/src/main/java/org/tasks/caldav/UpdateCalendarViewModel.kt
new file mode 100644
index 000000000..3d515b7ec
--- /dev/null
+++ b/app/src/main/java/org/tasks/caldav/UpdateCalendarViewModel.kt
@@ -0,0 +1,12 @@
+package org.tasks.caldav
+
+import org.tasks.data.CaldavAccount
+import org.tasks.data.CaldavCalendar
+import org.tasks.ui.CompletableViewModel
+
+class UpdateCalendarViewModel : CompletableViewModel<String?>() {
+    fun updateCalendar(
+            client: CaldavClient, account: CaldavAccount?, calendar: CaldavCalendar?, name: String?, color: Int) {
+        run { client.forCalendar(account, calendar).updateCollection(name, color) }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/etesync/AddEteSyncAccountViewModel.java b/app/src/main/java/org/tasks/etesync/AddEteSyncAccountViewModel.java
deleted file mode 100644
index 970cf89f9..000000000
--- a/app/src/main/java/org/tasks/etesync/AddEteSyncAccountViewModel.java
+++ /dev/null
@@ -1,17 +0,0 @@
-package org.tasks.etesync;
-
-import androidx.core.util.Pair;
-import com.etesync.journalmanager.UserInfoManager.UserInfo;
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class AddEteSyncAccountViewModel extends CompletableViewModel<Pair<UserInfo, String>> {
-  void addAccount(EteSyncClient client, String url, String username, String password) {
-    run(
-        () -> {
-          client.setForeground();
-          String token = client.forUrl(url, username, null, null).getToken(password);
-          return Pair.create(client.forUrl(url, username, null, token).getUserInfo(), token);
-        });
-  }
-}
diff --git a/app/src/main/java/org/tasks/etesync/AddEteSyncAccountViewModel.kt b/app/src/main/java/org/tasks/etesync/AddEteSyncAccountViewModel.kt
new file mode 100644
index 000000000..dc412776f
--- /dev/null
+++ b/app/src/main/java/org/tasks/etesync/AddEteSyncAccountViewModel.kt
@@ -0,0 +1,15 @@
+package org.tasks.etesync
+
+import androidx.core.util.Pair
+import com.etesync.journalmanager.UserInfoManager
+import org.tasks.ui.CompletableViewModel
+
+class AddEteSyncAccountViewModel : CompletableViewModel<Pair<UserInfoManager.UserInfo, String>>() {
+    fun addAccount(client: EteSyncClient, url: String?, username: String?, password: String?) {
+        run {
+            client.setForeground()
+            val token = client.forUrl(url, username, null, null).getToken(password)
+            Pair.create(client.forUrl(url, username, null, token!!).userInfo, token)
+        }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/etesync/CreateCalendarViewModel.java b/app/src/main/java/org/tasks/etesync/CreateCalendarViewModel.java
deleted file mode 100644
index afdac31c2..000000000
--- a/app/src/main/java/org/tasks/etesync/CreateCalendarViewModel.java
+++ /dev/null
@@ -1,11 +0,0 @@
-package org.tasks.etesync;
-
-import org.tasks.data.CaldavAccount;
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class CreateCalendarViewModel extends CompletableViewModel<String> {
-  void createCalendar(EteSyncClient client, CaldavAccount account, String name, int color) {
-    run(() -> client.forAccount(account).makeCollection(name, color));
-  }
-}
diff --git a/app/src/main/java/org/tasks/etesync/CreateCalendarViewModel.kt b/app/src/main/java/org/tasks/etesync/CreateCalendarViewModel.kt
new file mode 100644
index 000000000..613c79e77
--- /dev/null
+++ b/app/src/main/java/org/tasks/etesync/CreateCalendarViewModel.kt
@@ -0,0 +1,10 @@
+package org.tasks.etesync
+
+import org.tasks.data.CaldavAccount
+import org.tasks.ui.CompletableViewModel
+
+class CreateCalendarViewModel : CompletableViewModel<String?>() {
+    fun createCalendar(client: EteSyncClient, account: CaldavAccount?, name: String?, color: Int) {
+        run { client.forAccount(account!!).makeCollection(name, color) }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/etesync/CreateUserInfoViewModel.java b/app/src/main/java/org/tasks/etesync/CreateUserInfoViewModel.java
deleted file mode 100644
index d4f390b67..000000000
--- a/app/src/main/java/org/tasks/etesync/CreateUserInfoViewModel.java
+++ /dev/null
@@ -1,15 +0,0 @@
-package org.tasks.etesync;
-
-import org.tasks.data.CaldavAccount;
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class CreateUserInfoViewModel extends CompletableViewModel<String> {
-
-  void createUserInfo(EteSyncClient client, CaldavAccount caldavAccount, String derivedKey) {
-    run(() -> {
-      client.forAccount(caldavAccount).createUserInfo(derivedKey);
-      return derivedKey;
-    });
-  }
-}
diff --git a/app/src/main/java/org/tasks/etesync/CreateUserInfoViewModel.kt b/app/src/main/java/org/tasks/etesync/CreateUserInfoViewModel.kt
new file mode 100644
index 000000000..066d234d1
--- /dev/null
+++ b/app/src/main/java/org/tasks/etesync/CreateUserInfoViewModel.kt
@@ -0,0 +1,13 @@
+package org.tasks.etesync
+
+import org.tasks.data.CaldavAccount
+import org.tasks.ui.CompletableViewModel
+
+class CreateUserInfoViewModel : CompletableViewModel<String?>() {
+    fun createUserInfo(client: EteSyncClient, caldavAccount: CaldavAccount?, derivedKey: String?) {
+        run {
+            client.forAccount(caldavAccount!!).createUserInfo(derivedKey)
+            derivedKey
+        }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/etesync/EncryptionSettingsActivity.java b/app/src/main/java/org/tasks/etesync/EncryptionSettingsActivity.java
index fcb06ffa9..50935ca6a 100644
--- a/app/src/main/java/org/tasks/etesync/EncryptionSettingsActivity.java
+++ b/app/src/main/java/org/tasks/etesync/EncryptionSettingsActivity.java
@@ -23,6 +23,7 @@ import com.google.android.material.snackbar.Snackbar;
 import dagger.hilt.android.AndroidEntryPoint;
 import java.net.ConnectException;
 import javax.inject.Inject;
+import kotlin.Unit;
 import org.tasks.R;
 import org.tasks.data.CaldavAccount;
 import org.tasks.databinding.ActivityEtesyncEncryptionSettingsBinding;
@@ -95,13 +96,14 @@ public class EncryptionSettingsActivity extends ThemedInjectingAppCompatActivity
     return binding.progressBar.progressBar.getVisibility() == View.VISIBLE;
   }
 
-  private void returnDerivedKey(String derivedKey) {
+  private Unit returnDerivedKey(String derivedKey) {
     hideProgressIndicator();
 
     Intent result = new Intent();
     result.putExtra(EXTRA_DERIVED_KEY, derivedKey);
     setResult(RESULT_OK, result);
     finish();
+    return Unit.INSTANCE;
   }
 
   private void save() {
@@ -151,7 +153,7 @@ public class EncryptionSettingsActivity extends ThemedInjectingAppCompatActivity
     }
   }
 
-  protected void requestFailed(Throwable t) {
+  protected Unit requestFailed(Throwable t) {
     hideProgressIndicator();
 
     if (t instanceof HttpException) {
@@ -164,6 +166,7 @@ public class EncryptionSettingsActivity extends ThemedInjectingAppCompatActivity
       Timber.e(t);
       showSnackbar(R.string.error_adding_account, t.getMessage());
     }
+    return Unit.INSTANCE;
   }
 
   private void showSnackbar(int resId, Object... formatArgs) {
diff --git a/app/src/main/java/org/tasks/etesync/EteSyncAccountSettingsActivity.kt b/app/src/main/java/org/tasks/etesync/EteSyncAccountSettingsActivity.kt
index 3b2e269e1..55f0777c6 100644
--- a/app/src/main/java/org/tasks/etesync/EteSyncAccountSettingsActivity.kt
+++ b/app/src/main/java/org/tasks/etesync/EteSyncAccountSettingsActivity.kt
@@ -4,10 +4,9 @@ import android.app.Activity
 import android.content.Intent
 import android.os.Bundle
 import android.view.View
+import androidx.activity.viewModels
 import androidx.appcompat.widget.Toolbar
 import androidx.core.util.Pair
-import androidx.lifecycle.Observer
-import androidx.lifecycle.ViewModelProvider
 import butterknife.OnCheckedChanged
 import com.etesync.journalmanager.Crypto.CryptoManager
 import com.etesync.journalmanager.Exceptions.IntegrityException
@@ -29,31 +28,28 @@ import javax.inject.Inject
 class EteSyncAccountSettingsActivity : BaseCaldavAccountSettingsActivity(), Toolbar.OnMenuItemClickListener {
     @Inject lateinit var eteSyncClient: EteSyncClient
 
-    private var addAccountViewModel: AddEteSyncAccountViewModel? = null
-    private var updateAccountViewModel: UpdateEteSyncAccountViewModel? = null
+    private val addAccountViewModel: AddEteSyncAccountViewModel by viewModels()
+    private val updateAccountViewModel: UpdateEteSyncAccountViewModel by viewModels()
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         binding!!.repeat.visibility = View.GONE
         binding!!.showAdvanced.visibility = View.VISIBLE
         updateUrlVisibility()
-        val provider = ViewModelProvider(this)
-        addAccountViewModel = provider.get(AddEteSyncAccountViewModel::class.java)
-        updateAccountViewModel = provider.get(UpdateEteSyncAccountViewModel::class.java)
     }
 
     override fun onResume() {
         super.onResume()
         if (!isFinishing) {
-            addAccountViewModel!!.observe(this, Observer { userInfoAndToken: Pair<UserInfoManager.UserInfo, String> -> this.addAccount(userInfoAndToken) }, Observer { t: Throwable? -> requestFailed(t!!) })
-            updateAccountViewModel!!.observe(this, Observer { userInfoAndToken: Pair<UserInfoManager.UserInfo, String> -> this.updateAccount(userInfoAndToken) }, Observer { t: Throwable? -> requestFailed(t!!) })
+            addAccountViewModel.observe(this, { addAccount(it) }, { requestFailed(it) })
+            updateAccountViewModel.observe(this, { updateAccount(it) }, { requestFailed(it) })
         }
     }
 
     override fun onPause() {
         super.onPause()
-        addAccountViewModel!!.removeObserver(this)
-        updateAccountViewModel!!.removeObserver(this)
+        addAccountViewModel.removeObserver(this)
+        updateAccountViewModel.removeObserver(this)
     }
 
     override val description: Int
@@ -121,11 +117,11 @@ class EteSyncAccountSettingsActivity : BaseCaldavAccountSettingsActivity(), Tool
     }
 
     override fun addAccount(url: String?, username: String?, password: String?) {
-        addAccountViewModel!!.addAccount(eteSyncClient, url, username, password)
+        addAccountViewModel.addAccount(eteSyncClient, url, username, password)
     }
 
     override fun updateAccount(url: String?, username: String?, password: String?) {
-        updateAccountViewModel!!.updateAccount(
+        updateAccountViewModel.updateAccount(
                 eteSyncClient,
                 url,
                 username,
diff --git a/app/src/main/java/org/tasks/etesync/EteSyncClient.kt b/app/src/main/java/org/tasks/etesync/EteSyncClient.kt
index 26a437135..9aef98bea 100644
--- a/app/src/main/java/org/tasks/etesync/EteSyncClient.kt
+++ b/app/src/main/java/org/tasks/etesync/EteSyncClient.kt
@@ -74,8 +74,8 @@ class EteSyncClient {
             interceptor: DebugNetworkInterceptor,
             url: String?,
             username: String?,
-            encryptionPassword: String,
-            token: String,
+            encryptionPassword: String?,
+            token: String?,
             foreground: Boolean) {
         this.context = context
         this.encryption = encryption
@@ -119,7 +119,7 @@ class EteSyncClient {
     }
 
     @Throws(KeyManagementException::class, NoSuchAlgorithmException::class)
-    fun forUrl(url: String?, username: String?, encryptionPassword: String, token: String): EteSyncClient {
+    fun forUrl(url: String?, username: String?, encryptionPassword: String?, token: String?): EteSyncClient {
         return EteSyncClient(
                 context,
                 encryption,
diff --git a/app/src/main/java/org/tasks/etesync/UpdateCalendarViewModel.java b/app/src/main/java/org/tasks/etesync/UpdateCalendarViewModel.java
deleted file mode 100644
index c8e6c45c7..000000000
--- a/app/src/main/java/org/tasks/etesync/UpdateCalendarViewModel.java
+++ /dev/null
@@ -1,17 +0,0 @@
-package org.tasks.etesync;
-
-import org.tasks.data.CaldavAccount;
-import org.tasks.data.CaldavCalendar;
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class UpdateCalendarViewModel extends CompletableViewModel<String> {
-  void updateCalendar(
-      EteSyncClient client,
-      CaldavAccount account,
-      CaldavCalendar calendar,
-      String name,
-      int color) {
-    run(() -> client.forAccount(account).updateCollection(calendar, name, color));
-  }
-}
diff --git a/app/src/main/java/org/tasks/etesync/UpdateCalendarViewModel.kt b/app/src/main/java/org/tasks/etesync/UpdateCalendarViewModel.kt
new file mode 100644
index 000000000..8c3cd928b
--- /dev/null
+++ b/app/src/main/java/org/tasks/etesync/UpdateCalendarViewModel.kt
@@ -0,0 +1,16 @@
+package org.tasks.etesync
+
+import org.tasks.data.CaldavAccount
+import org.tasks.data.CaldavCalendar
+import org.tasks.ui.CompletableViewModel
+
+class UpdateCalendarViewModel : CompletableViewModel<String?>() {
+    fun updateCalendar(
+            client: EteSyncClient,
+            account: CaldavAccount?,
+            calendar: CaldavCalendar?,
+            name: String?,
+            color: Int) {
+        run { client.forAccount(account!!).updateCollection(calendar!!, name, color) }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/etesync/UpdateEteSyncAccountViewModel.java b/app/src/main/java/org/tasks/etesync/UpdateEteSyncAccountViewModel.java
deleted file mode 100644
index d6350d596..000000000
--- a/app/src/main/java/org/tasks/etesync/UpdateEteSyncAccountViewModel.java
+++ /dev/null
@@ -1,30 +0,0 @@
-package org.tasks.etesync;
-
-import static org.tasks.Strings.isNullOrEmpty;
-
-import androidx.annotation.Nullable;
-import androidx.core.util.Pair;
-import com.etesync.journalmanager.UserInfoManager.UserInfo;
-import org.tasks.ui.CompletableViewModel;
-
-@SuppressWarnings("WeakerAccess")
-public class UpdateEteSyncAccountViewModel extends CompletableViewModel<Pair<UserInfo, String>> {
-  void updateAccount(
-      EteSyncClient client,
-      String url,
-      String username,
-      @Nullable String password,
-      @Nullable String token) {
-    run(
-        () -> {
-          client.setForeground();
-          if (isNullOrEmpty(password)) {
-            return Pair.create(client.forUrl(url, username, null, token).getUserInfo(), token);
-          } else {
-            String newToken = client.forUrl(url, username, null, null).getToken(password);
-            return Pair.create(
-                client.forUrl(url, username, null, newToken).getUserInfo(), newToken);
-          }
-        });
-  }
-}
diff --git a/app/src/main/java/org/tasks/etesync/UpdateEteSyncAccountViewModel.kt b/app/src/main/java/org/tasks/etesync/UpdateEteSyncAccountViewModel.kt
new file mode 100644
index 000000000..f76972d03
--- /dev/null
+++ b/app/src/main/java/org/tasks/etesync/UpdateEteSyncAccountViewModel.kt
@@ -0,0 +1,21 @@
+package org.tasks.etesync
+
+import androidx.core.util.Pair
+import com.etesync.journalmanager.UserInfoManager
+import org.tasks.Strings.isNullOrEmpty
+import org.tasks.ui.CompletableViewModel
+
+class UpdateEteSyncAccountViewModel : CompletableViewModel<Pair<UserInfoManager.UserInfo, String>>() {
+    fun updateAccount(
+            client: EteSyncClient, url: String?, user: String?, pass: String?, token: String?) {
+        run {
+            client.setForeground()
+            if (isNullOrEmpty(pass)) {
+                Pair.create(client.forUrl(url, user, null, token).userInfo, token)
+            } else {
+                val newToken = client.forUrl(url, user, null, null).getToken(pass)
+                Pair.create(client.forUrl(url, user, null, newToken).userInfo, newToken)
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/org/tasks/preferences/fragments/Synchronization.kt b/app/src/main/java/org/tasks/preferences/fragments/Synchronization.kt
index a6ae4ded5..6d0abc837 100644
--- a/app/src/main/java/org/tasks/preferences/fragments/Synchronization.kt
+++ b/app/src/main/java/org/tasks/preferences/fragments/Synchronization.kt
@@ -16,6 +16,7 @@ import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import org.tasks.R
 import org.tasks.Strings.isNullOrEmpty
+import org.tasks.caldav.BaseCaldavAccountSettingsActivity
 import org.tasks.caldav.CaldavAccountSettingsActivity
 import org.tasks.data.CaldavAccount
 import org.tasks.data.CaldavAccount.Companion.TYPE_LOCAL
@@ -168,7 +169,7 @@ class Synchronization : InjectingPreferenceFragment() {
                     if (account.isCaldavAccount) CaldavAccountSettingsActivity::class.java
                     else EteSyncAccountSettingsActivity::class.java
                 )
-                intent.putExtra(CaldavAccountSettingsActivity.EXTRA_CALDAV_DATA, account)
+                intent.putExtra(BaseCaldavAccountSettingsActivity.EXTRA_CALDAV_DATA, account)
                 startActivityForResult(intent, REQUEST_CALDAV_SETTINGS)
                 false
             }
diff --git a/app/src/main/java/org/tasks/ui/CompletableViewModel.java b/app/src/main/java/org/tasks/ui/CompletableViewModel.java
deleted file mode 100644
index 6b34c7503..000000000
--- a/app/src/main/java/org/tasks/ui/CompletableViewModel.java
+++ /dev/null
@@ -1,58 +0,0 @@
-package org.tasks.ui;
-
-import static com.todoroo.andlib.utility.AndroidUtilities.assertMainThread;
-
-import androidx.lifecycle.LifecycleOwner;
-import androidx.lifecycle.MutableLiveData;
-import androidx.lifecycle.Observer;
-import androidx.lifecycle.ViewModel;
-import io.reactivex.Single;
-import io.reactivex.android.schedulers.AndroidSchedulers;
-import io.reactivex.disposables.CompositeDisposable;
-import io.reactivex.schedulers.Schedulers;
-import java.util.concurrent.Callable;
-
-public abstract class CompletableViewModel<T> extends ViewModel {
-  private final MutableLiveData<T> data = new MutableLiveData<>();
-  private final MutableLiveData<Throwable> error = new MutableLiveData<>();
-  private final CompositeDisposable disposables = new CompositeDisposable();
-  private boolean inProgress;
-
-  public void observe(
-      LifecycleOwner lifecycleOwner, Observer<T> dataObserver, Observer<Throwable> errorObserver) {
-    data.observe(lifecycleOwner, dataObserver);
-    error.observe(lifecycleOwner, errorObserver);
-  }
-
-  public boolean inProgress() {
-    return inProgress;
-  }
-
-  protected void run(Callable<T> callable) {
-    assertMainThread();
-
-    if (!inProgress) {
-      inProgress = true;
-      disposables.add(
-          Single.fromCallable(callable)
-              .subscribeOn(Schedulers.io())
-              .observeOn(AndroidSchedulers.mainThread())
-              .doFinally(
-                  () -> {
-                    assertMainThread();
-                    inProgress = false;
-                  })
-              .subscribe(data::setValue, error::setValue));
-    }
-  }
-
-  @Override
-  protected void onCleared() {
-    disposables.dispose();
-  }
-
-  public void removeObserver(LifecycleOwner owner) {
-    data.removeObservers(owner);
-    error.removeObservers(owner);
-  }
-}
diff --git a/app/src/main/java/org/tasks/ui/CompletableViewModel.kt b/app/src/main/java/org/tasks/ui/CompletableViewModel.kt
new file mode 100644
index 000000000..c4bf8a26d
--- /dev/null
+++ b/app/src/main/java/org/tasks/ui/CompletableViewModel.kt
@@ -0,0 +1,55 @@
+package org.tasks.ui
+
+import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.observe
+import com.todoroo.andlib.utility.AndroidUtilities
+import io.reactivex.Single
+import io.reactivex.android.schedulers.AndroidSchedulers
+import io.reactivex.disposables.CompositeDisposable
+import io.reactivex.schedulers.Schedulers
+
+abstract class CompletableViewModel<T> : ViewModel() {
+    private val data = MutableLiveData<T>()
+    private val error = MutableLiveData<Throwable>()
+    private val disposables = CompositeDisposable()
+    private var inProgress = false
+
+    fun observe(
+            lifecycleOwner: LifecycleOwner,
+            dataObserver: (T) -> Unit,
+            errorObserver: (Throwable) -> Unit) {
+        data.observe(lifecycleOwner, dataObserver)
+        error.observe(lifecycleOwner, errorObserver)
+    }
+
+    fun inProgress(): Boolean {
+        return inProgress
+    }
+
+    protected fun run(callable: () -> T) {
+        AndroidUtilities.assertMainThread()
+        if (!inProgress) {
+            inProgress = true
+            disposables.add(
+                    Single.fromCallable(callable)
+                            .subscribeOn(Schedulers.io())
+                            .observeOn(AndroidSchedulers.mainThread())
+                            .doFinally {
+                                AndroidUtilities.assertMainThread()
+                                inProgress = false
+                            }
+                            .subscribe({ value: T -> data.setValue(value) }) { value: Throwable -> error.setValue(value) })
+        }
+    }
+
+    override fun onCleared() {
+        disposables.dispose()
+    }
+
+    fun removeObserver(owner: LifecycleOwner) {
+        data.removeObservers(owner)
+        error.removeObservers(owner)
+    }
+}
\ No newline at end of file