Added central user credentials management

lib/api/marianumcloud/autocomplete/autocompleteApi.dart

@@ -3,13 +3,12 @@ import 'dart:io';
 
 import 'package:http/http.dart' as http;
 import 'package:http/http.dart';
-import 'package:shared_preferences/shared_preferences.dart';
 
+import '../../../model/accountData.dart';
 import 'autocompleteResponse.dart';
 
 class AutocompleteApi {
   Future<AutocompleteResponse> find(String query) async {
-    var preferences = await SharedPreferences.getInstance();
     Map<String, dynamic> getParameters = {
       "search": query,
       "itemType": " ",
@@ -22,7 +21,7 @@ class AutocompleteApi {
     headers.putIfAbsent("Accept", () => "application/json");
     headers.putIfAbsent("OCS-APIRequest", () => "true");
 
-    Uri endpoint = Uri.https("${preferences.getString("username")!}:${preferences.getString("password")!}@cloud.marianum-fulda.de", "/ocs/v2.php/core/autocomplete/get", getParameters);
+    Uri endpoint = Uri.https("${AccountData().buildHttpAuthString()}@cloud.marianum-fulda.de", "/ocs/v2.php/core/autocomplete/get", getParameters);
 
     Response response = await http.get(endpoint, headers: headers);
     if(response.statusCode != HttpStatus.ok) throw Exception("Api call failed with ${response.statusCode}: ${response.body}");

lib/api/marianumcloud/files-sharing/fileSharingApi.dart

@@ -3,19 +3,17 @@ import 'dart:io';
 
 import 'package:http/http.dart' as http;
 import 'package:http/http.dart';
-import 'package:shared_preferences/shared_preferences.dart';
 
+import '../../../model/accountData.dart';
 import 'fileSharingApiParams.dart';
 
 class FileSharingApi {
   Future<void> share(FileSharingApiParams query) async {
-    var preferences = await SharedPreferences.getInstance();
-
     Map<String, String> headers = {};
     headers.putIfAbsent("Accept", () => "application/json");
     headers.putIfAbsent("OCS-APIRequest", () => "true");
 
-    Uri endpoint = Uri.https("${preferences.getString("username")!}:${preferences.getString("password")!}@cloud.marianum-fulda.de", "/ocs/v2.php/apps/files_sharing/api/v1/shares", query.toJson().map((key, value) => MapEntry(key, value.toString())));
+    Uri endpoint = Uri.https("${AccountData().buildHttpAuthString()}@cloud.marianum-fulda.de", "/ocs/v2.php/apps/files_sharing/api/v1/shares", query.toJson().map((key, value) => MapEntry(key, value.toString())));
 
     log("request file share");
     Response response = await http.post(endpoint, headers: headers);

lib/api/marianumcloud/talk/talkApi.dart

@@ -1,8 +1,8 @@
 import 'dart:developer';
 
 import 'package:http/http.dart' as http;
-import 'package:shared_preferences/shared_preferences.dart';
 
+import '../../../model/accountData.dart';
 import '../../apiError.dart';
 import '../../apiParams.dart';
 import '../../apiRequest.dart';
@@ -32,9 +32,7 @@ abstract class TalkApi<T> extends ApiRequest {
       getParameters?.update(key, (value) => value.toString());
     });
 
-    SharedPreferences preferences = await SharedPreferences.getInstance();
+    Uri endpoint = Uri.https("${AccountData().buildHttpAuthString()}@cloud.marianum-fulda.de", "/ocs/v2.php/apps/spreed/api/$path", getParameters);
-
-    Uri endpoint = Uri.https("${preferences.getString("username")!}:${preferences.getString("password")!}@cloud.marianum-fulda.de", "/ocs/v2.php/apps/spreed/api/$path", getParameters);
 
     headers ??= {};
     headers?.putIfAbsent("Accept", () => "application/json");

lib/api/marianumcloud/webdav/webdavApi.dart

@@ -1,6 +1,6 @@
 import 'package:nextcloud/nextcloud.dart';
-import 'package:shared_preferences/shared_preferences.dart';
 
+import '../../../model/accountData.dart';
 import '../../apiRequest.dart';
 import '../../apiResponse.dart';
 
@@ -17,14 +17,10 @@ abstract class WebdavApi<T> extends ApiRequest {
   static Future<String> webdavConnectString = buildWebdavConnectString();
 
   static Future<WebDavClient> establishWebdavConnection() async {
-    SharedPreferences preferences = await SharedPreferences.getInstance();
+    return NextcloudClient("https://cloud.marianum-fulda.de/", username: AccountData().getUsername(), password: AccountData().getPassword(), loginName: AccountData().getUsername()).webdav;
-
-    return NextcloudClient("https://cloud.marianum-fulda.de/", username: preferences.getString("username"), password: preferences.getString("password"), loginName: preferences.getString("username")).webdav;
   }
 
   static Future<String> buildWebdavConnectString() async {
-    SharedPreferences preferences = await SharedPreferences.getInstance();
+    return "https://${AccountData().buildHttpAuthString()}@cloud.marianum-fulda.de/remote.php/dav/files/${AccountData().getUsername()}/";
-
-    return "https://${preferences.getString("username")}:${preferences.getString("password")}@cloud.marianum-fulda.de/remote.php/dav/files/${preferences.getString("username")}/";
   }
 }

lib/api/webuntis/queries/authenticate/authenticate.dart

@@ -2,8 +2,7 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:developer';
 
-import 'package:shared_preferences/shared_preferences.dart';
+import '../../../../model/accountData.dart';
-
 import '../../webuntisApi.dart';
 import 'authenticateParams.dart';
 import 'authenticateResponse.dart';
@@ -28,12 +27,10 @@ class Authenticate extends WebuntisApi {
   static AuthenticateResponse? _lastResponse;
 
   static Future<void> createSession() async {
-    SharedPreferences preferences = await SharedPreferences.getInstance();
-
     _lastResponse = await Authenticate(
         AuthenticateParams(
-          user: preferences.getString("username")!,
+          user: AccountData().getUsername(),
-          password: preferences.getString("password")!,
+          password: AccountData().getPassword(),
         )
     ).run();
   }

lib/app.dart

@@ -22,14 +22,16 @@ class App extends StatefulWidget {
 class _AppState extends State<App> {
   int currentPage = 0;
   late Timer refetchChats;
+  late Timer updateTimings;
 
   @override
   void initState() {
-    Timer.periodic(const Duration(seconds: 30), (Timer t) => setState((){}));
-
     WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
       Provider.of<ChatListProps>(context, listen: false).run();
     });
+
+    updateTimings = Timer.periodic(const Duration(seconds: 30), (Timer t) => setState((){}));
+
     refetchChats = Timer.periodic(const Duration(minutes: 1), (timer) {
       if(!context.mounted) return;
       Provider.of<ChatListProps>(context, listen: false).run();
@@ -107,6 +109,7 @@ class _AppState extends State<App> {
   @override
   void dispose() {
     refetchChats.cancel();
+    updateTimings.cancel();
     super.dispose();
   }
 }

lib/main.dart

@@ -4,10 +4,10 @@ import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:jiffy/jiffy.dart';
 import 'package:provider/provider.dart';
-import 'package:shared_preferences/shared_preferences.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 
 import 'app.dart';
+import 'model/accountData.dart';
 import 'model/accountModel.dart';
 import 'model/chatList/chatListProps.dart';
 import 'model/chatList/chatProps.dart';
@@ -18,7 +18,7 @@ import 'storage/base/settingsProvider.dart';
 import 'theming/darkAppTheme.dart';
 import 'theming/lightAppTheme.dart';
 import 'view/login/login.dart';
-import 'widget/errorView.dart';
+import 'widget/placeholderView.dart';
 
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
@@ -27,7 +27,7 @@ Future<void> main() async {
   SecurityContext.defaultContext.setTrustedCertificatesBytes(data.buffer.asUint8List());
 
   ErrorWidget.builder = (error) {
-    return ErrorView(icon: Icons.phonelink_erase_rounded, text: error.toString());
+    return PlaceholderView(icon: Icons.phonelink_erase_rounded, text: error.toString());
   };
 
   runApp(
@@ -56,27 +56,22 @@ class Main extends StatefulWidget {
 }
 
 class _MainState extends State<Main> {
-
-  final Future<SharedPreferences> _storage = SharedPreferences.getInstance();
-
   @override
   void initState() {
-    super.initState();
     Jiffy.setLocale("de");
-    _storage.then((SharedPreferences preferences) => preferences.getBool("loggedIn") ?? false).then((value) => {
+
-      if(value) {
+    SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp, DeviceOrientation.portraitDown]);
-        Provider.of<AccountModel>(context, listen: false).login()
+
-      } else {
+    AccountData().waitForPopulation().then((value) {
-        Provider.of<AccountModel>(context, listen: false).logout()
+      Provider.of<AccountModel>(context, listen: false)
-      }
+          .setState(value ? AccountModelState.loggedIn : AccountModelState.loggedOut);
     });
 
+    super.initState();
   }
 
   @override
   Widget build(BuildContext context) {
-    SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);
-
     return Directionality(
       textDirection: TextDirection.ltr,
       child: Consumer<SettingsProvider>(
@@ -93,7 +88,6 @@ class _MainState extends State<Main> {
             ],
             locale: const Locale('de'),
 
-
             title: 'Marianum Fulda',
 
             themeMode: settings.val().appTheme,
@@ -101,21 +95,15 @@ class _MainState extends State<Main> {
             darkTheme: DarkAppTheme.theme,
 
 
-              home: FutureBuilder<SharedPreferences>(
+            home: Consumer<AccountModel>(
-                future: _storage,
-                builder: (BuildContext context, AsyncSnapshot<SharedPreferences> snapshot) {
-
-                  if(snapshot.hasData) {
-                    return Consumer<AccountModel>(
               builder: (context, accountModel, child) {
-                        return accountModel.isLoggedIn ? const App() : const Login();
+                switch(accountModel.state) {
-                      },
+                  case AccountModelState.loggedIn: return const App();
-                    );
+                  case AccountModelState.loggedOut: return const Login();
-                  } else {
+                  case AccountModelState.undefined: return const PlaceholderView(icon: Icons.timer, text: "Daten werden geladen");
-                    return const Center(child: CircularProgressIndicator());
                 }
               },
-              )
+            ),
           );
         },
       ),

lib/model/accountData.dart

@@ -0,0 +1,78 @@
+import 'dart:async';
+
+import 'package:flutter/cupertino.dart';
+import 'package:provider/provider.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+import 'accountModel.dart';
+
+class AccountData {
+  static const _usernameField = "username";
+  static const _passwordField = "password";
+  
+  static final AccountData _instance = AccountData._construct();
+  final Future<SharedPreferences> _storage = SharedPreferences.getInstance();
+  Completer<void> _populated = Completer();
+
+  factory AccountData() {
+    return _instance;
+  }
+
+  AccountData._construct() {
+    _updateFromStorage();
+  }
+
+  String? _username;
+  String? _password;
+
+  String getUsername() {
+    if(_username == null) throw Exception("Username not initialized");
+    return _username!;
+  }
+
+  String getPassword() {
+    if(_password == null) throw Exception("Password not initialized");
+    return _password!;
+  }
+
+  Future<void> setData(BuildContext context, String username, String password) async {
+    SharedPreferences storage = await _storage;
+
+    storage.setString(_usernameField, username);
+    storage.setString(_passwordField, password);
+    await _updateFromStorage();
+  }
+
+  void removeData(BuildContext context) async {
+    _populated = Completer();
+    Provider.of<AccountModel>(context, listen: false).setState(AccountModelState.loggedOut);
+
+    SharedPreferences storage = await _storage;
+    storage.remove(_usernameField);
+    storage.remove(_passwordField);
+  }
+
+  Future<void> _updateFromStorage() async {
+    SharedPreferences storage = await _storage;
+    await storage.reload();
+    if(storage.containsKey(_usernameField) && storage.containsKey(_passwordField)) {
+      _username = storage.getString(_usernameField);
+      _password = storage.getString(_passwordField);
+      _populated.complete();
+    }
+  }
+
+  Future<bool> waitForPopulation() async {
+    await _populated.future;
+    return isPopulated();
+  }
+
+  bool isPopulated() {
+    return _username != null && _password != null;
+  }
+
+  String buildHttpAuthString() {
+    if(!isPopulated()) throw Exception("AccountData (e.g. username or password) is not initialized!");
+    return "$_username:$_password";
+  }
+}

lib/model/accountModel.dart

@@ -1,17 +1,17 @@
 import 'package:flutter/cupertino.dart';
 
 class AccountModel extends ChangeNotifier {
-  bool _isLoggedIn = false;
+  AccountModelState _accountState = AccountModelState.undefined;
+  AccountModelState get state => _accountState;
 
-  bool get isLoggedIn => _isLoggedIn;
+  void setState(AccountModelState state) {
-
+    _accountState = state;
-  void logout() {
-    _isLoggedIn = false;
-    notifyListeners();
-  }
-
-  void login() {
-    _isLoggedIn = true;
     notifyListeners();
   }
 }
+
+enum AccountModelState {
+  undefined,
+  loggedIn,
+  loggedOut,
+}

lib/storage/base/settingsProvider.dart

@@ -1,9 +1,9 @@
 import 'dart:convert';
 import 'dart:developer';
 import 'package:flutter/material.dart';
-import 'package:marianum_mobile/storage/file/fileSettings.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
+import '../file/fileSettings.dart';
 import '../gradeAverages/gradeAveragesSettings.dart';
 import '../talk/talkSettings.dart';
 import '../timetable/timetableSettings.dart';

lib/view/login/login.dart

@@ -1,15 +1,11 @@
 
-import 'dart:developer';
-
 import 'package:flutter/material.dart';
 import 'package:flutter_login/flutter_login.dart';
 import 'package:provider/provider.dart';
-import 'package:shared_preferences/shared_preferences.dart';
 
-import '../../api/apiError.dart';
 import '../../api/webuntis/queries/authenticate/authenticateParams.dart';
 import '../../api/webuntis/queries/authenticate/authenticate.dart';
-import '../../api/webuntis/webuntisError.dart';
+import '../../model/accountData.dart';
 import '../../model/accountModel.dart';
 
 class Login extends StatefulWidget {
@@ -27,8 +23,7 @@ class _LoginState extends State<Login> {
   }
 
   Future<String?> _login(LoginData data) async {
-    SharedPreferences preferences = await SharedPreferences.getInstance();
+    AccountData().removeData(context);
-    preferences.setBool("loggedIn", false);
 
     try {
       await Authenticate(
@@ -36,22 +31,16 @@ class _LoginState extends State<Login> {
           user: data.name,
           password: data.password,
         )
-      ).run().then((value) => {
+      ).run().then((value) async {
-        log(value.sessionId)
+        await AccountData().setData(context, data.name, data.password);
-      });
-    } on WebuntisError catch(e) {
-      return e.toString();
-    } on ApiError catch(e) {
-      return e.toString();
-    }
 
         setState(() {
           displayDisclaimerText = false;
         });
-
+      });
-    preferences.setBool("loggedIn", true);
+    } catch(e) {
-    preferences.setString("username", data.name);
+      return e.toString();
-    preferences.setString("password", data.password);
+    }
 
     return null;
   }
@@ -69,7 +58,7 @@ class _LoginState extends State<Login> {
 
       userValidator: _checkInput,
       passwordValidator: _checkInput,
-      onSubmitAnimationCompleted: () => Provider.of<AccountModel>(context, listen: false).login(),
+      onSubmitAnimationCompleted: () => Provider.of<AccountModel>(context, listen: false).setState(AccountModelState.loggedIn),
 
       onLogin: _login,
       onSignup: null,

lib/view/pages/files/files.dart

@@ -4,8 +4,6 @@ import 'dart:io';
 
 import 'package:flutter/material.dart';
 import 'package:loader_overlay/loader_overlay.dart';
-import 'package:marianum_mobile/storage/base/settingsProvider.dart';
-import 'package:marianum_mobile/widget/loadingSpinner.dart';
 import 'package:provider/provider.dart';
 
 import '../../../api/marianumcloud/webdav/queries/listFiles/cacheableFile.dart';
@@ -13,7 +11,9 @@ import '../../../api/marianumcloud/webdav/queries/listFiles/listFilesCache.dart'
 import '../../../api/marianumcloud/webdav/queries/listFiles/listFilesResponse.dart';
 import '../../../api/marianumcloud/webdav/webdavApi.dart';
 import '../../../model/files/filesProps.dart';
-import '../../../widget/errorView.dart';
+import '../../../storage/base/settingsProvider.dart';
+import '../../../widget/loadingSpinner.dart';
+import '../../../widget/placeholderView.dart';
 import '../../../widget/filePick.dart';
 import 'fileUploadDialog.dart';
 import 'fileElement.dart';
@@ -224,7 +224,7 @@ class _FilesState extends State<Files> {
         },
         child: const Icon(Icons.add),
       ),
-      body: data == null ? const LoadingSpinner() : data!.files.isEmpty ? const ErrorView(icon: Icons.folder_off_rounded, text: "Der Ordner ist leer") : LoaderOverlay(
+      body: data == null ? const LoadingSpinner() : data!.files.isEmpty ? const PlaceholderView(icon: Icons.folder_off_rounded, text: "Der Ordner ist leer") : LoaderOverlay(
         child: RefreshIndicator(
           onRefresh: () {
             _query();

lib/view/pages/more/message/message.dart

@@ -1,10 +1,9 @@
-import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:marianum_mobile/widget/loadingSpinner.dart';
 import 'package:provider/provider.dart';
 
 import '../../../../api/mhsl/message/getMessages/getMessagesResponse.dart';
 import '../../../../model/message/messageProps.dart';
+import '../../../../widget/loadingSpinner.dart';
 import 'messageView.dart';
 
 

lib/view/pages/talk/chatBubble.dart

@@ -4,12 +4,12 @@ import 'package:flowder/flowder.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:jiffy/jiffy.dart';
-import 'package:marianum_mobile/api/marianumcloud/talk/deleteMessage/deleteMessage.dart';
-import 'package:marianum_mobile/model/chatList/chatProps.dart';
 import 'package:provider/provider.dart';
 
 import '../../../api/marianumcloud/talk/chat/getChatResponse.dart';
+import '../../../api/marianumcloud/talk/deleteMessage/deleteMessage.dart';
 import '../../../api/marianumcloud/talk/room/getRoomResponse.dart';
+import '../../../model/chatList/chatProps.dart';
 import '../../../theming/appTheme.dart';
 import '../../../widget/debug/debugTile.dart';
 import '../files/fileElement.dart';

lib/view/pages/talk/chatList.dart

@@ -1,14 +1,14 @@
 
 import 'dart:async';
 import 'package:flutter/material.dart';
-import 'package:marianum_mobile/api/marianumcloud/talk/createRoom/createRoomParams.dart';
-import 'package:marianum_mobile/widget/confirmDialog.dart';
-import 'package:marianum_mobile/widget/loadingSpinner.dart';
 import 'package:provider/provider.dart';
 
 import '../../../api/marianumcloud/talk/createRoom/createRoom.dart';
+import '../../../api/marianumcloud/talk/createRoom/createRoomParams.dart';
 import '../../../model/chatList/chatListProps.dart';
 import '../../../storage/base/settingsProvider.dart';
+import '../../../widget/confirmDialog.dart';
+import '../../../widget/loadingSpinner.dart';
 import 'chatTile.dart';
 import 'joinChat.dart';
 import 'searchChat.dart';

lib/view/pages/talk/chatView.dart

@@ -2,13 +2,13 @@
 import 'package:flutter/material.dart';
 import 'package:jiffy/jiffy.dart';
 import 'package:loader_overlay/loader_overlay.dart';
-import 'package:marianum_mobile/widget/loadingSpinner.dart';
 import 'package:provider/provider.dart';
 
 import '../../../api/marianumcloud/talk/chat/getChatResponse.dart';
 import '../../../api/marianumcloud/talk/room/getRoomResponse.dart';
 import '../../../theming/appTheme.dart';
 import '../../../model/chatList/chatProps.dart';
+import '../../../widget/loadingSpinner.dart';
 import 'chatBubble.dart';
 import 'chatTextfield.dart';
 

lib/view/pages/talk/joinChat.dart

@@ -5,7 +5,7 @@ import 'package:flutter/material.dart';
 
 import '../../../api/marianumcloud/autocomplete/autocompleteApi.dart';
 import '../../../api/marianumcloud/autocomplete/autocompleteResponse.dart';
-import '../../../widget/errorView.dart';
+import '../../../widget/placeholderView.dart';
 
 class JoinChat extends SearchDelegate<String> {
   CancelableOperation<AutocompleteResponse>? future;
@@ -47,7 +47,7 @@ class JoinChat extends SearchDelegate<String> {
     if(future != null) future!.cancel();
 
     if(query.isEmpty) {
-      return const ErrorView(
+      return const PlaceholderView(
         text: "Suche nach benutzern",
         icon: Icons.person_search_outlined,
       );
@@ -81,7 +81,7 @@ class JoinChat extends SearchDelegate<String> {
           );
         } else if(snapshot.hasError) {
           log(snapshot.error.toString());
-          return ErrorView(text: snapshot.error.toString());
+          return PlaceholderView(icon: Icons.search_off, text: snapshot.error.toString());
         }
 
         return const Center(child: CircularProgressIndicator());

lib/view/pages/timetable/timetable.dart

@@ -2,7 +2,6 @@
 import 'dart:developer';
 
 import 'package:flutter/material.dart';
-import 'package:marianum_mobile/widget/loadingSpinner.dart';
 import 'package:provider/provider.dart';
 import 'package:syncfusion_flutter_calendar/calendar.dart';
 
@@ -11,7 +10,8 @@ import '../../../api/webuntis/queries/getRooms/getRoomsResponse.dart';
 import '../../../api/webuntis/queries/getSubjects/getSubjectsResponse.dart';
 import '../../../model/timetable/timetableProps.dart';
 import '../../../storage/base/settingsProvider.dart';
-import '../../../widget/errorView.dart';
+import '../../../widget/loadingSpinner.dart';
+import '../../../widget/placeholderView.dart';
 import 'appointmenetComponent.dart';
 import 'appointmentDetails.dart';
 import 'timeRegionComponent.dart';
@@ -68,7 +68,7 @@ class _TimetableState extends State<Timetable> {
           GetHolidaysResponse holidays = value.getHolidaysResponse;
 
           if(value.hasError) {
-            return ErrorView(
+            return PlaceholderView(
               icon: Icons.calendar_month,
               text: "Webuntis error: ${value.error.toString()}",
             );

lib/view/settings/settings.dart

@@ -5,7 +5,7 @@ import 'package:package_info/package_info.dart';
 import 'package:provider/provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
-import '../../model/accountModel.dart';
+import '../../model/accountData.dart';
 import '../../storage/base/settingsProvider.dart';
 import '../../theming/appTheme.dart';
 import '../../widget/confirmDialog.dart';
@@ -52,9 +52,9 @@ class _SettingsState extends State<Settings> {
                     onConfirm: () {
                       SharedPreferences.getInstance().then((value) => {
                         value.clear(),
-                      }).then((value) => {
+                      }).then((value) {
-                        Provider.of<AccountModel>(context, listen: false).logout(),
+                        AccountData().removeData(context);
-                        Navigator.popUntil(context, (route) => !Navigator.canPop(context)),
+                        Navigator.popUntil(context, (route) => !Navigator.canPop(context));
                       });
                     },
                   ),

lib/widget/debug/cacheView.dart

@@ -7,7 +7,7 @@ import 'package:flutter/services.dart';
 import 'package:jiffy/jiffy.dart';
 import 'package:localstore/localstore.dart';
 
-import '../../../widget/errorView.dart';
+import '../../../widget/placeholderView.dart';
 import 'jsonViewer.dart';
 
 class CacheView extends StatefulWidget {
@@ -93,7 +93,7 @@ class _CacheViewState extends State<CacheView> {
             );
           } else {
             return const Center(
-              child: ErrorView(icon: Icons.hourglass_empty, text: "Keine Daten"),
+              child: PlaceholderView(icon: Icons.hourglass_empty, text: "Keine Daten"),
             );
           }
         },

lib/widget/errorView.dart

@@ -1,31 +0,0 @@
-import 'package:flutter/material.dart';
-
-class ErrorView extends StatelessWidget {
-  final IconData icon;
-  final String text;
-  const ErrorView({Key? key, this.icon = Icons.report_gmailerrorred, this.text = "Es ist ein Fehler aufgetreten!"}) : super(key: key);
-
-  @override
-  Widget build(BuildContext context) {
-    return Center(
-      child: Container(
-        margin: const EdgeInsets.only(top: 100, left: 20, right: 20),
-        child: Column(
-          children: [
-            Container(
-              margin: const EdgeInsets.all(30),
-              child: Icon(icon, color: Colors.grey, size: 60),
-            ),
-            Text(text,
-              style: const TextStyle(
-                fontSize: 20,
-                color: Colors.grey,
-              ),
-              textAlign: TextAlign.center,
-            ),
-          ],
-        ),
-      ),
-    );
-  }
-}

lib/widget/placeholderView.dart

@@ -0,0 +1,34 @@
+import 'package:flutter/material.dart';
+
+class PlaceholderView extends StatelessWidget {
+  final IconData icon;
+  final String text;
+  const PlaceholderView({Key? key, required this.icon, required this.text}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return DefaultTextStyle(
+      style: const TextStyle(),
+      child: Center(
+        child: Container(
+          margin: const EdgeInsets.only(top: 100, left: 20, right: 20),
+          child: Column(
+            children: [
+              Container(
+                margin: const EdgeInsets.all(30),
+                child: Icon(icon, color: Colors.grey, size: 60),
+              ),
+              Text(text,
+                style: const TextStyle(
+                  fontSize: 20,
+                  color: Colors.grey,
+                ),
+                textAlign: TextAlign.center,
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}