Make Backend a stateful widget

lib/app.dart

@@ -15,7 +15,7 @@ class _AppState extends State<App> with SingleTickerProviderStateMixin {
   final nestedNavigator = GlobalKey<NavigatorState>();
 
   AnimationController playerBarAnimation;
-  Backend backend;
+  BackendState backend;
   StreamSubscription<bool> playerActiveSubscription;
 
   @override

lib/backend.dart

@@ -3,21 +3,34 @@ import 'package:rxdart/rxdart.dart';
 
 import 'database.dart';
 
-class Backend extends InheritedWidget {
+class Backend extends StatefulWidget {
-  static Backend of(BuildContext context) =>
-      context.dependOnInheritedWidgetOfExactType<Backend>();
-
   final Widget child;
 
+  Backend({
+    @required this.child,
+  });
+
+  @override
+  BackendState createState() => BackendState();
+
+  static BackendState of(BuildContext context) =>
+      context.dependOnInheritedWidgetOfExactType<_InheritedBackend>().state;
+}
+
+class BackendState extends State<Backend> {
   final db = Database('musicus.sqlite');
 
   final playerActive = BehaviorSubject.seeded(false);
   final playing = BehaviorSubject.seeded(false);
   final position = BehaviorSubject.seeded(0.0);
 
-  Backend({
+  @override
-    @required this.child,
+  Widget build(BuildContext context) {
-  }) : super(child: child);
+    return _InheritedBackend(
+      child: widget.child,
+      state: this,
+    );
+  }
 
   void startPlayer() {
     playerActive.add(true);
@@ -44,10 +57,17 @@ class Backend extends InheritedWidget {
       }
     }
   }
+}
+
+class _InheritedBackend extends InheritedWidget {
+  final Widget child;
+  final BackendState state;
+
+  _InheritedBackend({
+    @required this.child,
+    @required this.state,
+  }) : super(child: child);
 
   @override
-  bool updateShouldNotify(Backend old) =>
+  bool updateShouldNotify(_InheritedBackend old) => state != old.state;
-      playerActive != old.playerActive ||
-      playing != old.playing ||
-      position != old.position;
 }

lib/editors/work.dart

@@ -209,7 +209,7 @@ class WorkEditor extends StatefulWidget {
 class _WorkEditorState extends State<WorkEditor> {
   final titleController = TextEditingController();
 
-  Backend backend;
+  BackendState backend;
 
   String title = '';
   Person composer;

lib/screens/program.dart

@@ -11,7 +11,7 @@ class ProgramScreen extends StatefulWidget {
 }
 
 class _ProgramScreenState extends State<ProgramScreen> {
-  Backend backend;
+  BackendState backend;
   StreamSubscription<double> positionSubscription;
   double position = 0.0;
   bool seeking = false;

lib/widgets/play_pause_button.dart

@@ -12,7 +12,7 @@ class PlayPauseButton extends StatefulWidget {
 class _PlayPauseButtonState extends State<PlayPauseButton>
     with SingleTickerProviderStateMixin {
   AnimationController playPauseAnimation;
-  Backend backend;
+  BackendState backend;
   StreamSubscription<bool> playingSubscription;
 
   @override