Use an InheritedWidget instead of passing the callbacks

This simplifies the code quite a bit, at the cost of using this
strange flutter magic of an 'InheritedWidget'.

It basically make a class a global variable.

lib/app.dart

@@ -1,51 +1,14 @@
-import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
-import 'package:uuid/uuid.dart';
-
-import 'package:journal/file_storage.dart';
-import 'package:journal/note.dart';
 import 'package:journal/screens/home_screen.dart';
 
-class JournalApp extends StatefulWidget {
-  final FileStorage fileStorage;
-
-  JournalApp({@required this.fileStorage});
-
-  @override
-  JournalAppState createState() {
-    return new JournalAppState();
-  }
-}
-
-class JournalAppState extends State<JournalApp> {
-  AppState appState = AppState.loading();
-
-  @override
-  void initState() {
-    super.initState();
-
-    widget.fileStorage.loadNotes().then((loadedNotes) {
-      setState(() {
-        appState = AppState(notes: loadedNotes);
-      });
-    }).catchError((err) {
-      setState(() {
-        print("Got Error");
-        print(err);
-        appState.isLoading = false;
-      });
-    });
-  }
+class JournalApp extends StatelessWidget {
+  JournalApp();
 
   @override
   Widget build(BuildContext context) {
     return new MaterialApp(
       title: 'Journal',
-      home: new HomeScreen(
-        appState: appState,
-        noteAdder: addNote,
-        noteRemover: removeNote,
-      ),
+      home: new HomeScreen(),
       theme: new ThemeData(
         brightness: Brightness.dark,
         primaryColor: Colors.lightBlue[800],
@@ -53,33 +16,4 @@ class JournalAppState extends State<JournalApp> {
       ),
     );
   }
-
-  @override
-  void setState(VoidCallback fn) {
-    super.setState(fn);
-
-    widget.fileStorage.saveNotes(appState.notes);
-  }
-
-  void addNote(Note note) {
-    print("Adding a note " + note.toString());
-    setState(() {
-      note.id = new Uuid().v4();
-      appState.notes.insert(0, note);
-    });
-  }
-
-  void removeNote(Note note) {
-    setState(() {
-      appState.notes.remove(note);
-    });
-  }
-
-  // FIXME: Implement this!
-  void updateNote(Note note) {
-    setState(() {
-      //appState.notes.
-      //appState.notes.remove(note);
-    });
-  }
 }

lib/file_storage.dart

@@ -10,7 +10,7 @@ import './note.dart';
 class FileStorage {
   final Future<Directory> Function() getDirectory;
 
-  FileStorage({@required this.getDirectory});
+  const FileStorage({@required this.getDirectory});
 
   Future<List<Note>> loadNotes() async {
     final dir = await getDirectory();

lib/main.dart

@@ -1,13 +1,8 @@
-import 'dart:async';
-import 'dart:io';
-
 import 'package:flutter/material.dart';
 //import 'package:http/http.dart' as http;
-import 'package:journal/app.dart';
-import 'package:path_provider/path_provider.dart';
-import 'package:path/path.dart' as p;
 
-import 'package:journal/file_storage.dart';
+import 'package:journal/app.dart';
+import 'package:journal/state_container.dart';
 
 /*
 import 'note.dart';
@@ -26,17 +21,7 @@ Future<List<Note>> fetchNotes() async {
 */
 
 void main() {
-  runApp(new JournalApp(
-    fileStorage: FileStorage(
-      getDirectory: getNotesDir,
-    ),
+  runApp(new StateContainer(
+    child: JournalApp(),
   ));
 }
-
-Future<Directory> getNotesDir() async {
-  var appDir = await getApplicationDocumentsDirectory();
-  var dir = new Directory(p.join(appDir.path, "notes"));
-  await dir.create();
-
-  return dir;
-}

lib/note_editor.dart

@@ -1,20 +1,19 @@
 import 'package:flutter/material.dart';
-import 'package:flutter/foundation.dart';
 import 'package:intl/intl.dart';
 import 'package:journal/note.dart';
+import 'package:journal/state_container.dart';
 
 class NoteEditor extends StatelessWidget {
   static final GlobalKey<FormFieldState<String>> noteTextKey =
       GlobalKey<FormFieldState<String>>();
-  final NoteAdder noteAdder;
   final DateTime _createdAt;
 
-  NoteEditor({
-    @required this.noteAdder,
-  }) : _createdAt = new DateTime.now();
+  NoteEditor() : _createdAt = new DateTime.now();
 
   @override
   Widget build(BuildContext context) {
+    final container = StateContainer.of(context);
+
     var bodyWidget = new Container(
       child: new TextFormField(
         key: noteTextKey,
@@ -44,7 +43,7 @@ class NoteEditor extends StatelessWidget {
               createdAt: _createdAt,
               body: body,
             );
-            noteAdder(note);
+            container.addNote(note);
 
             Navigator.pop(context);
           }),

lib/screens/home_screen.dart

@@ -1,24 +1,18 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/foundation.dart';
 
+import 'package:journal/state_container.dart';
 import 'package:journal/widgets/journal_list.dart';
 import 'package:journal/note.dart';
 import 'package:journal/note_editor.dart';
 import 'package:journal/note_viewer.dart';
 
 class HomeScreen extends StatelessWidget {
-  final AppState appState;
-  final NoteAdder noteAdder;
-  final NoteRemover noteRemover;
-
-  HomeScreen({
-    @required this.appState,
-    @required this.noteAdder,
-    @required this.noteRemover,
-  });
-
   @override
   Widget build(BuildContext context) {
+    final container = StateContainer.of(context);
+    final appState = container.appState;
+
     var createButton = new FloatingActionButton(
       onPressed: () => _newPost(context),
       child: new Icon(Icons.add),
@@ -49,7 +43,6 @@ class HomeScreen extends StatelessWidget {
       body: new JournalList(
         notes: appState.notes,
         noteSelectedFunction: (note) => _noteSelected(note, context),
-        noteRemover: noteRemover,
       ),
     );
   }
@@ -61,10 +54,7 @@ class HomeScreen extends StatelessWidget {
   }
 
   void _newPost(BuildContext context) {
-    var route = new MaterialPageRoute(
-        builder: (context) => new NoteEditor(
-              noteAdder: noteAdder,
-            ));
+    var route = new MaterialPageRoute(builder: (context) => new NoteEditor());
     Navigator.of(context).push(route);
   }
 }

lib/state_container.dart

@@ -0,0 +1,117 @@
+import 'dart:async';
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:path_provider/path_provider.dart';
+import 'package:path/path.dart' as p;
+import 'package:uuid/uuid.dart';
+
+import 'package:journal/note.dart';
+import 'package:journal/file_storage.dart';
+
+Future<Directory> getNotesDir() async {
+  var appDir = await getApplicationDocumentsDirectory();
+  var dir = new Directory(p.join(appDir.path, "notes"));
+  await dir.create();
+
+  return dir;
+}
+
+class StateContainer extends StatefulWidget {
+  final FileStorage fileStorage;
+  final Widget child;
+
+  StateContainer({
+    @required this.child,
+    this.fileStorage = const FileStorage(
+      getDirectory: getNotesDir,
+    ),
+  });
+
+  static StateContainerState of(BuildContext context) {
+    return (context.inheritFromWidgetOfExactType(_InheritedStateContainer)
+            as _InheritedStateContainer)
+        .data;
+  }
+
+  @override
+  State<StatefulWidget> createState() {
+    return StateContainerState();
+  }
+}
+
+class StateContainerState extends State<StateContainer> {
+  AppState appState = AppState.loading();
+
+  @override
+  void initState() {
+    super.initState();
+
+    widget.fileStorage.loadNotes().then((loadedNotes) {
+      setState(() {
+        appState = AppState(notes: loadedNotes);
+      });
+    }).catchError((err) {
+      setState(() {
+        print("Got Error");
+        print(err);
+        appState.isLoading = false;
+      });
+    });
+  }
+
+  @override
+  void setState(VoidCallback fn) {
+    super.setState(fn);
+
+    widget.fileStorage.saveNotes(appState.notes);
+  }
+
+  void addNote(Note note) {
+    print("Adding a note " + note.toString());
+    setState(() {
+      note.id = new Uuid().v4();
+      appState.notes.insert(0, note);
+    });
+  }
+
+  void removeNote(Note note) {
+    setState(() {
+      appState.notes.remove(note);
+    });
+  }
+
+  // FIXME: Implement this!
+  void updateNote(Note note) {
+    setState(() {
+      //appState.notes.
+      //appState.notes.remove(note);
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return _InheritedStateContainer(
+      data: this,
+      child: widget.child,
+    );
+  }
+}
+
+class _InheritedStateContainer extends InheritedWidget {
+  final StateContainerState data;
+
+  _InheritedStateContainer({
+    Key key,
+    @required this.data,
+    @required Widget child,
+  }) : super(key: key, child: child);
+
+  // Note: we could get fancy here and compare whether the old AppState is
+  // different than the current AppState. However, since we know this is the
+  // root Widget, when we make changes we also know we want to rebuild Widgets
+  // that depend on the StateContainer.
+  @override
+  bool updateShouldNotify(_InheritedStateContainer old) => true;
+}

lib/widgets/journal_list.dart

@@ -3,12 +3,12 @@ import 'package:flutter/foundation.dart';
 import 'package:intl/intl.dart';
 
 import 'package:journal/note.dart';
+import 'package:journal/state_container.dart';
 
 typedef void NoteSelectedFunction(Note note);
 
 class JournalList extends StatelessWidget {
   final NoteSelectedFunction noteSelectedFunction;
-  final NoteRemover noteRemover;
   final List<Note> notes;
 
   final _biggerFont = const TextStyle(fontSize: 18.0);
@@ -16,11 +16,12 @@ class JournalList extends StatelessWidget {
   JournalList({
     @required this.notes,
     @required this.noteSelectedFunction,
-    @required this.noteRemover,
   });
 
   @override
   Widget build(BuildContext context) {
+    final container = StateContainer.of(context);
+
     return new ListView.builder(
       padding: const EdgeInsets.all(8.0),
       itemBuilder: (context, i) {
@@ -35,7 +36,7 @@ class JournalList extends StatelessWidget {
           child: _buildRow(context, note),
           background: new Container(color: Colors.red),
           onDismissed: (direction) {
-            noteRemover(note);
+            container.removeNote(note);
 
             Scaffold
                 .of(context)