Cleanup to navigation_and_routing sample (#881)

- make more things private and final, where possible
- remove unused members
- used expression bodies, where possible

navigation_and_routing/lib/src/screens/author_details.dart

@@ -17,25 +17,23 @@ class AuthorDetailsScreen extends StatelessWidget {
   }) : super(key: key);
 
   @override
-  Widget build(BuildContext context) {
-    return Scaffold(
-      appBar: AppBar(
-        title: Text(author.name),
-      ),
-      body: Center(
-        child: Column(
-          children: [
-            Expanded(
-              child: BookList(
-                books: author.books,
-                onTap: (book) {
-                  RouteStateScope.of(context)!.go('/book/${book.id}');
-                },
-              ),
-            ),
-          ],
+  Widget build(BuildContext context) => Scaffold(
+        appBar: AppBar(
+          title: Text(author.name),
         ),
-      ),
-    );
-  }
+        body: Center(
+          child: Column(
+            children: [
+              Expanded(
+                child: BookList(
+                  books: author.books,
+                  onTap: (book) {
+                    RouteStateScope.of(context)!.go('/book/${book.id}');
+                  },
+                ),
+              ),
+            ],
+          ),
+        ),
+      );
 }

navigation_and_routing/lib/src/screens/authors.dart

@@ -14,17 +14,15 @@ class AuthorsScreen extends StatelessWidget {
   const AuthorsScreen({Key? key}) : super(key: key);
 
   @override
-  Widget build(BuildContext context) {
-    return Scaffold(
-      appBar: AppBar(
-        title: Text(title),
-      ),
-      body: AuthorList(
-        authors: LibraryScope.of(context).allAuthors,
-        onTap: (author) {
-          RouteStateScope.of(context)!.go('/author/${author.id}');
-        },
-      ),
-    );
-  }
+  Widget build(BuildContext context) => Scaffold(
+        appBar: AppBar(
+          title: Text(title),
+        ),
+        body: AuthorList(
+          authors: LibraryScope.of(context).allAuthors,
+          onTap: (author) {
+            RouteStateScope.of(context)!.go('/author/${author.id}');
+          },
+        ),
+      );
 }

navigation_and_routing/lib/src/screens/book_details.dart

@@ -45,21 +45,18 @@ class BookDetailsScreen extends StatelessWidget {
               onPressed: () {
                 Navigator.of(context).push<void>(
                   MaterialPageRoute<void>(
-                    builder: (context) {
-                      return AuthorDetailsScreen(author: book!.author);
-                    },
+                    builder: (context) =>
+                        AuthorDetailsScreen(author: book!.author),
                   ),
                 );
               },
             ),
             Link(
               uri: Uri.parse('/author/${book!.author.id}'),
-              builder: (context, followLink) {
-                return TextButton(
-                  onPressed: followLink,
-                  child: const Text('View author (Link)'),
-                );
-              },
+              builder: (context, followLink) => TextButton(
+                onPressed: followLink,
+                child: const Text('View author (Link)'),
+              ),
             ),
           ],
         ),

navigation_and_routing/lib/src/screens/books.dart

@@ -10,11 +10,8 @@ import '../widgets/book_list.dart';
 import '../widgets/library_scope.dart';
 
 class BooksScreen extends StatefulWidget {
-  final ParsedRoute currentRoute;
-
   const BooksScreen({
     Key? key,
-    required this.currentRoute,
   }) : super(key: key);
 
   @override
@@ -36,7 +33,7 @@ class _BooksScreenState extends State<BooksScreen>
   void didChangeDependencies() {
     super.didChangeDependencies();
 
-    final newPath = routeState.route.pathTemplate;
+    final newPath = _routeState.route.pathTemplate;
     if (newPath.startsWith('/books/popular')) {
       _tabController.index = 0;
     } else if (newPath.startsWith('/books/new')) {
@@ -96,35 +93,23 @@ class _BooksScreenState extends State<BooksScreen>
     );
   }
 
-  String get title {
-    switch (_tabController.index) {
-      case 1:
-        return 'New';
-      case 2:
-        return 'All';
-      case 0:
-      default:
-        return 'Popular';
-    }
-  }
-
-  RouteState get routeState => RouteStateScope.of(context)!;
+  RouteState get _routeState => RouteStateScope.of(context)!;
 
   void _handleBookTapped(Book book) {
-    routeState.go('/book/${book.id}');
+    _routeState.go('/book/${book.id}');
   }
 
   void _handleTabIndexChanged() {
     switch (_tabController.index) {
       case 1:
-        routeState.go('/books/new');
+        _routeState.go('/books/new');
         break;
       case 2:
-        routeState.go('/books/all');
+        _routeState.go('/books/all');
         break;
       case 0:
       default:
-        routeState.go('/books/popular');
+        _routeState.go('/books/popular');
         break;
     }
   }

navigation_and_routing/lib/src/screens/navigator.dart

@@ -30,10 +30,10 @@ class BookstoreNavigator extends StatefulWidget {
 }
 
 class _BookstoreNavigatorState extends State<BookstoreNavigator> {
-  final signInKey = const ValueKey('Sign in');
-  final scaffoldKey = const ValueKey<String>('App scaffold');
-  final bookDetailsKey = const ValueKey<String>('Book details screen');
-  final authorDetailsKey = const ValueKey<String>('Author details screen');
+  final _signInKey = const ValueKey('Sign in');
+  final _scaffoldKey = const ValueKey<String>('App scaffold');
+  final _bookDetailsKey = const ValueKey<String>('Book details screen');
+  final _authorDetailsKey = const ValueKey<String>('Author details screen');
 
   @override
   Widget build(BuildContext context) {
@@ -60,12 +60,12 @@ class _BookstoreNavigatorState extends State<BookstoreNavigator> {
         // When a page that is stacked on top of the scaffold is popped, display
         // the /books or /authors tab in BookstoreScaffold.
         if (route.settings is Page &&
-            (route.settings as Page).key == bookDetailsKey) {
+            (route.settings as Page).key == _bookDetailsKey) {
           routeState.go('/books/popular');
         }
 
         if (route.settings is Page &&
-            (route.settings as Page).key == authorDetailsKey) {
+            (route.settings as Page).key == _authorDetailsKey) {
           routeState.go('/authors');
         }
 
@@ -75,7 +75,7 @@ class _BookstoreNavigatorState extends State<BookstoreNavigator> {
         if (routeState.route.pathTemplate == '/signin')
           // Display the sign in screen.
           FadeTransitionPage<void>(
-            key: signInKey,
+            key: _signInKey,
             child: SignInScreen(
               onSignIn: (credentials) async {
                 var signedIn = await authState.signIn(
@@ -89,21 +89,21 @@ class _BookstoreNavigatorState extends State<BookstoreNavigator> {
         else ...[
           // Display the app
           FadeTransitionPage<void>(
-            key: scaffoldKey,
+            key: _scaffoldKey,
             child: const BookstoreScaffold(),
           ),
           // Add an additional page to the stack if the user is viewing a book
           // or an author
           if (selectedBook != null)
             MaterialPage<void>(
-              key: bookDetailsKey,
+              key: _bookDetailsKey,
               child: BookDetailsScreen(
                 book: selectedBook,
               ),
             )
           else if (selectedAuthor != null)
             MaterialPage<void>(
-              key: authorDetailsKey,
+              key: _authorDetailsKey,
               child: AuthorDetailsScreen(
                 author: selectedAuthor,
               ),

navigation_and_routing/lib/src/screens/scaffold_body.dart

@@ -41,9 +41,9 @@ class BookstoreScaffoldBody extends StatelessWidget {
           )
         else if (currentRoute.pathTemplate.startsWith('/books') ||
             currentRoute.pathTemplate == '/')
-          FadeTransitionPage<void>(
-            key: const ValueKey('books'),
-            child: BooksScreen(currentRoute: currentRoute),
+          const FadeTransitionPage<void>(
+            key: ValueKey('books'),
+            child: BooksScreen(),
           )
 
         // Avoid building a Navigator with an empty `pages` list when the

navigation_and_routing/lib/src/screens/settings.dart

@@ -17,26 +17,24 @@ class SettingsScreen extends StatefulWidget {
 
 class _SettingsScreenState extends State<SettingsScreen> {
   @override
-  Widget build(BuildContext context) {
-    return Scaffold(
-      body: SafeArea(
-        child: SingleChildScrollView(
-          child: Align(
-            alignment: Alignment.topCenter,
-            child: ConstrainedBox(
-              constraints: const BoxConstraints(maxWidth: 400),
-              child: const Card(
-                child: Padding(
-                  padding: EdgeInsets.symmetric(vertical: 18, horizontal: 12),
-                  child: SettingsContent(),
+  Widget build(BuildContext context) => Scaffold(
+        body: SafeArea(
+          child: SingleChildScrollView(
+            child: Align(
+              alignment: Alignment.topCenter,
+              child: ConstrainedBox(
+                constraints: const BoxConstraints(maxWidth: 400),
+                child: const Card(
+                  child: Padding(
+                    padding: EdgeInsets.symmetric(vertical: 18, horizontal: 12),
+                    child: SettingsContent(),
+                  ),
                 ),
               ),
             ),
           ),
         ),
-      ),
-    );
-  }
+      );
 }
 
 class SettingsContent extends StatelessWidget {
@@ -45,57 +43,53 @@ class SettingsContent extends StatelessWidget {
   }) : super(key: key);
 
   @override
-  Widget build(BuildContext context) {
-    return Column(
-      children: [
-        ...[
-          Text(
-            'Settings',
-            style: Theme.of(context).textTheme.headline4,
-          ),
-          ElevatedButton(
-            onPressed: () {
-              BookstoreAuthScope.of(context)!.signOut();
-            },
-            child: const Text('Sign out'),
-          ),
-          Link(
-            uri: Uri.parse('/book/0'),
-            builder: (context, followLink) {
-              return TextButton(
+  Widget build(BuildContext context) => Column(
+        children: [
+          ...[
+            Text(
+              'Settings',
+              style: Theme.of(context).textTheme.headline4,
+            ),
+            ElevatedButton(
+              onPressed: () {
+                BookstoreAuthScope.of(context)!.signOut();
+              },
+              child: const Text('Sign out'),
+            ),
+            Link(
+              uri: Uri.parse('/book/0'),
+              builder: (context, followLink) => TextButton(
                 onPressed: followLink,
                 child: const Text('Go directly to /book/0 (Link)'),
-              );
-            },
-          ),
-          TextButton(
-            child: const Text('Go directly to /book/0 (RouteState)'),
-            onPressed: () {
-              RouteStateScope.of(context)!.go('/book/0');
-            },
-          ),
-        ].map((w) => Padding(padding: const EdgeInsets.all(8), child: w)),
-        TextButton(
-          onPressed: () => showDialog<String>(
-            context: context,
-            builder: (context) => AlertDialog(
-              title: const Text('Alert!'),
-              content: const Text('The alert description goes here.'),
-              actions: <Widget>[
-                TextButton(
-                  onPressed: () => Navigator.pop(context, 'Cancel'),
-                  child: const Text('Cancel'),
-                ),
-                TextButton(
-                  onPressed: () => Navigator.pop(context, 'OK'),
-                  child: const Text('OK'),
-                ),
-              ],
+              ),
             ),
-          ),
-          child: const Text('Show Dialog'),
-        )
-      ],
-    );
-  }
+            TextButton(
+              child: const Text('Go directly to /book/0 (RouteState)'),
+              onPressed: () {
+                RouteStateScope.of(context)!.go('/book/0');
+              },
+            ),
+          ].map((w) => Padding(padding: const EdgeInsets.all(8), child: w)),
+          TextButton(
+            onPressed: () => showDialog<String>(
+              context: context,
+              builder: (context) => AlertDialog(
+                title: const Text('Alert!'),
+                content: const Text('The alert description goes here.'),
+                actions: <Widget>[
+                  TextButton(
+                    onPressed: () => Navigator.pop(context, 'Cancel'),
+                    child: const Text('Cancel'),
+                  ),
+                  TextButton(
+                    onPressed: () => Navigator.pop(context, 'OK'),
+                    child: const Text('OK'),
+                  ),
+                ],
+              ),
+            ),
+            child: const Text('Show Dialog'),
+          )
+        ],
+      );
 }

navigation_and_routing/lib/src/screens/sign_in.dart

@@ -29,43 +29,41 @@ class _SignInScreenState extends State<SignInScreen> {
   final _passwordController = TextEditingController();
 
   @override
-  Widget build(BuildContext context) {
-    return Scaffold(
-      body: Center(
-        child: Card(
-          child: Container(
-            constraints: BoxConstraints.loose(const Size(600, 600)),
-            padding: const EdgeInsets.all(8),
-            child: Column(
-              mainAxisAlignment: MainAxisAlignment.center,
-              mainAxisSize: MainAxisSize.min,
-              children: [
-                Text('Sign in', style: Theme.of(context).textTheme.headline4),
-                TextField(
-                  decoration: const InputDecoration(labelText: 'Username'),
-                  controller: _usernameController,
-                ),
-                TextField(
-                  decoration: const InputDecoration(labelText: 'Password'),
-                  obscureText: true,
-                  controller: _passwordController,
-                ),
-                Padding(
-                  padding: const EdgeInsets.all(16),
-                  child: TextButton(
-                    onPressed: () async {
-                      widget.onSignIn(Credentials(
-                          _usernameController.value.text,
-                          _passwordController.value.text));
-                    },
-                    child: const Text('Sign in'),
+  Widget build(BuildContext context) => Scaffold(
+        body: Center(
+          child: Card(
+            child: Container(
+              constraints: BoxConstraints.loose(const Size(600, 600)),
+              padding: const EdgeInsets.all(8),
+              child: Column(
+                mainAxisAlignment: MainAxisAlignment.center,
+                mainAxisSize: MainAxisSize.min,
+                children: [
+                  Text('Sign in', style: Theme.of(context).textTheme.headline4),
+                  TextField(
+                    decoration: const InputDecoration(labelText: 'Username'),
+                    controller: _usernameController,
                   ),
-                ),
-              ],
+                  TextField(
+                    decoration: const InputDecoration(labelText: 'Password'),
+                    obscureText: true,
+                    controller: _passwordController,
+                  ),
+                  Padding(
+                    padding: const EdgeInsets.all(16),
+                    child: TextButton(
+                      onPressed: () async {
+                        widget.onSignIn(Credentials(
+                            _usernameController.value.text,
+                            _passwordController.value.text));
+                      },
+                      child: const Text('Sign in'),
+                    ),
+                  ),
+                ],
+              ),
             ),
           ),
         ),
-      ),
-    );
-  }
+      );
 }