implemented scheduled updates for widgets

android/app/src/main/AndroidManifest.xml

@@ -1,5 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+>
 
     <!--
      Required to query activities that can process text, see:
@@ -19,6 +22,7 @@
     <uses-permission android:name="android.permission.INTERNET" />
 
     <application
+        tools:replace="android:label"
         android:name="${applicationName}"
         android:icon="@mipmap/ic_launcher"
         android:label="Marianum Fulda">

android/build.gradle

@@ -2,6 +2,11 @@ allprojects {
     repositories {
         google()
         mavenCentral()
+
+        // [required] background_fetch
+        maven {
+            url "${project(':background_fetch').projectDir}/libs"
+        }
     }
 }
 

lib/app.dart

@@ -24,6 +24,7 @@ import 'storage/base/settingsProvider.dart';
 import 'view/pages/overhang.dart';
 
 class App extends StatefulWidget {
+  static GlobalKey appContext = GlobalKey();
   const App({super.key});
 
   @override
@@ -31,7 +32,6 @@ class App extends StatefulWidget {
 }
 
 class _AppState extends State<App> with WidgetsBindingObserver {
-
   late Timer refetchChats;
   late Timer updateTimings;
 

lib/background_tasks/scheduledTask.dart

@@ -0,0 +1,64 @@
+import 'dart:developer';
+
+import 'package:background_fetch/background_fetch.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+import '../app.dart';
+import '../homescreen_widgets/timetable/timetableHomeWidget.dart';
+
+class ScheduledTask {
+  static final String fetchApiLastRunTimestampKey = 'fetchApiLastRunTimestamp';
+
+  static Future<void> configure() async {
+    var status = await BackgroundFetch.configure(BackgroundFetchConfig(
+        minimumFetchInterval: 15,
+        stopOnTerminate: false,
+        enableHeadless: true,
+        requiresBatteryNotLow: false,
+        requiresCharging: false,
+        requiresStorageNotLow: false,
+        requiresDeviceIdle: false,
+        requiredNetworkType: NetworkType.ANY,
+        startOnBoot: true,
+    ), (String taskId) async {
+      log('Background fetch started with id $taskId');
+      await ScheduledTask.backgroundFetch();
+      BackgroundFetch.finish(taskId);
+    }, (String taskId) async {
+      log('Background fetch stopped because of an timeout with id $taskId');
+      BackgroundFetch.finish(taskId);
+    });
+
+    log('Background Fetch-API status: $status');
+  }
+
+  // called periodically, iOS and Android
+  static Future<void> backgroundFetch() async {
+    var sp = await SharedPreferences.getInstance();
+    var history = sp.getStringList(fetchApiLastRunTimestampKey) ?? List.empty(growable: true);
+    history.add(DateTime.now().toIso8601String());
+    try {
+      TimetableHomeWidget.update(App.appContext.currentContext!);
+    } on Exception catch(e) {
+      history.add('Got Error:');
+      history.add(e.toString());
+      history.add('--- EXCEPTION END ---');
+    }
+    sp.setStringList(fetchApiLastRunTimestampKey, history.take(100).toList());
+  }
+
+  // only Android, starts when app is terminated
+  @pragma('vm:entry-point')
+  static Future<void> headless(HeadlessTask task) async {
+    var taskId = task.taskId;
+    var isTimeout = task.timeout;
+    if (isTimeout) {
+      log('Background fetch headless task timed-out: $taskId');
+      BackgroundFetch.finish(taskId);
+      return;
+    }
+    log('Background fetch headless event received.');
+    await backgroundFetch();
+    BackgroundFetch.finish(taskId);
+  }
+}

lib/homescreen_widgets/timetable/timetableHomeWidget.dart

@@ -1,13 +1,14 @@
+import 'dart:async';
 import 'dart:convert';
 import 'dart:developer';
 
 import 'package:flutter/material.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:home_widget/home_widget.dart';
-import 'package:provider/provider.dart';
 import 'package:screenshot/screenshot.dart';
 import 'package:syncfusion_flutter_calendar/calendar.dart';
 
+import '../../model/accountData.dart';
 import '../../model/timetable/timetableProps.dart';
 import '../../storage/base/settingsProvider.dart';
 import '../../theming/darkAppTheme.dart';
@@ -15,23 +16,31 @@ import '../../theming/lightAppTheme.dart';
 import '../../view/pages/timetable/calendar.dart';
 
 class TimetableHomeWidget {
+  static Future<void> update(BuildContext context) async {
+    await AccountData().waitForPopulation();
+    var data = TimetableProps();
+    var settings = SettingsProvider();
+    settings.waitForPopulation();
+    var completer = Completer();
 
-  static void update(BuildContext context) {
+    data.addListener(() async {
-    var data = Provider.of<TimetableProps>(context, listen: false);
+      if(completer.isCompleted) return;
-    var settings = Provider.of<SettingsProvider>(context, listen: false);
+      if(data.primaryLoading()) return;
+      await _generate(data, settings);
+      completer.complete();
+    });
 
-    if(data.primaryLoading()) {
+    data.run();
-      log('Could not generate widget screen because no data was found!');
+    await completer.future;
-      return;
+  }
-    }
 
+  static Future<void> _generate(TimetableProps data, SettingsProvider settings) async {
     log('Generating widget screen...');
     var screenshotController = ScreenshotController();
     var calendarController = CalendarController();
     calendarController.displayDate = DateTime.now().copyWith(hour: 07, minute: 00);
 
-    screenshotController.captureFromWidget(
+    var imageData = await screenshotController.captureFromWidget(
-      delay: Duration(milliseconds: 100),
       SizedBox(
         height: 700,
         width: 300,
@@ -55,7 +64,7 @@ class TimetableHomeWidget {
               home: ClipRRect(
                 borderRadius: BorderRadius.circular(20),
                 child: Scaffold(
-                body: Calendar(
+                  body: Calendar(
                     controller: calendarController,
                     timetableProps: data,
                     settings: settings,
@@ -67,10 +76,10 @@ class TimetableHomeWidget {
           ),
         ),
       ),
-    ).then((value) {
+    );
-      HomeWidget.saveWidgetData<String>('screen', base64.encode(value));
+
-      HomeWidget.updateWidget(name: 'TimetableWidget');
+    HomeWidget.saveWidgetData<String>('screen', base64.encode(imageData));
-      log('Widget screen successfully updated! (${value.length})');
+    HomeWidget.updateWidget(name: 'TimetableWidget');
-    });
+    log('Widget screen successfully updated! (${imageData.length})');
   }
 }

lib/main.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 import 'dart:developer';
 import 'dart:io';
 
+import 'package:background_fetch/background_fetch.dart';
 import 'package:firebase_core/firebase_core.dart';
 import 'package:firebase_messaging/firebase_messaging.dart';
 import 'package:flutter/foundation.dart';
@@ -17,6 +18,7 @@ import 'package:provider/provider.dart';
 
 import 'api/mhsl/breaker/getBreakers/getBreakersResponse.dart';
 import 'app.dart';
+import 'background_tasks/scheduledTask.dart';
 import 'firebase_options.dart';
 import 'model/accountData.dart';
 import 'model/accountModel.dart';
@@ -84,6 +86,8 @@ Future<void> main() async {
         child: const Main(),
       )
   );
+
+  BackgroundFetch.registerHeadlessTask(ScheduledTask.headless);
 }
 
 class Main extends StatefulWidget {
@@ -111,6 +115,7 @@ class _MainState extends State<Main> {
       Provider.of<BreakerProps>(context, listen: false).run();
     });
 
+    ScheduledTask.configure();
     super.initState();
   }
 
@@ -146,7 +151,7 @@ class _MainState extends State<Main> {
                   child: Consumer<AccountModel>(
                     builder: (context, accountModel, child) {
                       switch(accountModel.state) {
-                        case AccountModelState.loggedIn: return const App();
+                        case AccountModelState.loggedIn: return App(key: App.appContext);
                         case AccountModelState.loggedOut: return const Login();
                         case AccountModelState.undefined: return const PlaceholderView(icon: Icons.timer, text: 'Daten werden geladen');
                       }

lib/storage/base/settingsProvider.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:convert';
 import 'dart:developer';
 import 'package:easy_debounce/easy_debounce.dart';
@@ -13,6 +14,8 @@ class SettingsProvider extends ChangeNotifier {
   late SharedPreferences _storage;
   late Settings _settings = DefaultSettings.get();
 
+  final Completer<void> _populated = Completer();
+
   Settings val({bool write = false}) {
     if(write) {
       notifyListeners();
@@ -56,6 +59,7 @@ class SettingsProvider extends ChangeNotifier {
     }
 
     notifyListeners();
+    _populated.complete();
   }
 
   Future<void> update() async {
@@ -77,4 +81,8 @@ class SettingsProvider extends ChangeNotifier {
 
     return mergedMap;
   }
+
+  Future<void> waitForPopulation() async {
+    await _populated.future;
+  }
 }

lib/view/settings/devToolsSettings.dart

@@ -1,14 +1,18 @@
 
+import 'package:background_fetch/background_fetch.dart';
 import 'package:filesize/filesize.dart';
 import 'package:flutter/material.dart';
 import 'package:hydrated_bloc/hydrated_bloc.dart';
 import 'package:provider/provider.dart';
+import 'package:shared_preferences/shared_preferences.dart';
 
+import '../../background_tasks/scheduledTask.dart';
 import '../../storage/base/settingsProvider.dart';
 import '../../widget/centeredLeading.dart';
 import '../../widget/confirmDialog.dart';
 import '../../widget/debug/cacheView.dart';
 import '../../widget/debug/jsonViewer.dart';
+import '../../widget/infoDialog.dart';
 
 class DevToolsSettings extends StatefulWidget {
   final SettingsProvider settings;
@@ -22,6 +26,84 @@ class _DevToolsSettingsState extends State<DevToolsSettings> {
   @override
   Widget build(BuildContext context) => Column(
       children: [
+        ListTile(
+          leading: const CenteredLeading(Icon(Icons.task_outlined)),
+          title: const Text('Background app fetch task'),
+          trailing: const Icon(Icons.arrow_right),
+          onTap: () {
+            showDialog(context: context, builder: (context) => AlertDialog(
+              title: Text('Background fetch task'),
+              content: Column(
+                mainAxisSize: MainAxisSize.min,
+                mainAxisAlignment: MainAxisAlignment.start,
+                children: [
+                  FutureBuilder(future: BackgroundFetch.status, builder: (context, snapshot) {
+                    if(snapshot.hasData) {
+                      var fetchStatus = switch(snapshot.data) {
+                        BackgroundFetch.STATUS_AVAILABLE => 'STATUS_AVAILABLE, Background updates are available for the app.',
+                        BackgroundFetch.STATUS_DENIED => 'STATUS_DENIED, The user explicitly disabled background behavior for this app or for the whole system.',
+                        BackgroundFetch.STATUS_RESTRICTED => 'STATUS_RESTRICTED, Background updates are unavailable and the user cannot enable them again. For example, this status can occur when parental controls are in effect for the current user.',
+                        _ => 'UNKNOWN',
+                      };
+                      return Text('(${snapshot.data}): $fetchStatus');
+                    }
+                    return LinearProgressIndicator();
+                  }),
+                  const Divider(),
+                  const Text('There is no indicator if the Fetch-API is currently running or not!'),
+                  const Divider(),
+                  FutureBuilder(
+                    future: SharedPreferences.getInstance(),
+                    builder: (context, snapshot) {
+                      if(!snapshot.hasData) return LinearProgressIndicator();
+                      return Text('Last fetch timestamp: ${snapshot.data?.getStringList(ScheduledTask.fetchApiLastRunTimestampKey)?.last ?? 'No entry'}');
+                    },
+                  )
+                ],
+              ),
+              actions: [
+                FutureBuilder(future: SharedPreferences.getInstance(), builder: (context, snapshot) {
+                  if(!snapshot.hasData) return LinearProgressIndicator();
+                  return TextButton(
+                    onPressed: () {
+                      InfoDialog.show(
+                        context,
+                        (snapshot.data!.getStringList(ScheduledTask.fetchApiLastRunTimestampKey) ?? []).reversed.join('\n')
+                      );
+                    },
+                    child: Text('Fetch history')
+                  );
+                }),
+                TextButton(
+                  onPressed: () => ConfirmDialog(
+                    title: 'Warning',
+                    content: 'Background Fetch worker will be started! This basically happens on every app startup.',
+                    onConfirm: BackgroundFetch.start
+                  ).asDialog(context),
+                  child: Text('Fetch-API Start')
+                ),
+                TextButton(
+                  onPressed: () => ConfirmDialog(
+                    title: 'Warning',
+                    content: 'Background Fetch worker will be terminated. This will result in outdated Information when App is not in foreground!',
+                    onConfirm: BackgroundFetch.stop
+                  ).asDialog(context),
+                  child: Text('Fetch-API Stop')
+                ),
+                TextButton(
+                  onPressed: () => ConfirmDialog(
+                    title: 'Warning',
+                    content: 'Background fetch will run now! This happens in the application layer and does not interact with the Fetch-API!',
+                    confirmButton: 'Run',
+                    onConfirm: ScheduledTask.backgroundFetch
+                  ).asDialog(context),
+                  child: Text('Run task manually')
+                ),
+                TextButton(onPressed: () => Navigator.of(context).pop(), child: Text('Zurück'))
+              ],
+            ));
+          },
+        ),
         ListTile(
           leading: const CenteredLeading(Icon(Icons.speed_outlined)),
           title: const Text('Performance overlays'),

pubspec.yaml

@@ -103,6 +103,7 @@ dependencies:
   uuid: ^4.5.1
   home_widget: ^0.7.0+1
   screenshot: ^3.0.0
+  background_fetch: ^1.3.7
 
 dev_dependencies:
   flutter_test: