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Created March 24, 2021 08:59
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Flutter Navigator v2.0 parent delegates child to pop example
import 'package:flutter/material.dart';
void main() => runApp(NestedRouterDemo());
//Model???
class Book {
final String title;
final String author;
Book(this.title, this.author);
}
//Main app Class must be statefull
class NestedRouterDemo extends StatefulWidget {
@override
_NestedRouterDemoState createState() => _NestedRouterDemoState();
}
class _NestedRouterDemoState extends State<NestedRouterDemo> {
@override
Widget build(BuildContext context) {
return MaterialApp.router(
routeInformationParser: BookRouteInformationParser(),
routerDelegate: BookRouterDelegate(),
);
}
}
//App state
class BookAppState extends ChangeNotifier {
int _selectedPageIndex;
Book _selectedBook;
final List<Book> books = [
Book('Sítio do picapau amarelo', 'Monteiro Lobato'),
Book('Memórias Póstunas de Brás Cubas', 'Machado de Assis'),
Book('Capitães de reia', 'Jorge Amado')
];
BookAppState() : _selectedPageIndex = 0;
//Index Getter and setters
int get selectedPageIndex => _selectedPageIndex;
set selectedPageIndex(int index) {
_selectedPageIndex = index;
if (_selectedPageIndex == 1) {
//Remove to keep the selected book
selectedBook = null;
}
notifyListeners();
}
//Book Getter and setters
Book get selectedBook => _selectedBook;
set selectedBook(Book book) {
_selectedBook = book;
notifyListeners();
}
int getSelectedBookById() {
if (!books.contains(_selectedBook)) {
return 0;
}
return books.indexOf(_selectedBook);
}
void setSelectedBookById(int id) {
if (id < 0 || id > books.length - 1) {
return;
}
_selectedBook = books[id];
notifyListeners();
}
}
//Parser mandatory
class BookRouteInformationParser extends RouteInformationParser<BookRoutePath> {
@override
Future<BookRoutePath> parseRouteInformation(
RouteInformation routeInformation) async {
//Parse URL
final uri = Uri.parse(routeInformation.location);
//Return Settings page path
if (uri.pathSegments.isNotEmpty && uri.pathSegments.first == 'settings') {
return BooksSettingsPath();
} else {
// Return Book path
if (uri.pathSegments.length >= 2) {
if (uri.pathSegments[0] == 'book') {
return BooksDetailsPath(int.tryParse(uri.pathSegments[1]));
}
}
//Anything else, return Homepage
return BooksListPath();
}
}
//TODO: search
@override
RouteInformation restoreRouteInformation(BookRoutePath configuration) {
if (configuration is BooksListPath) {
return RouteInformation(location: '/home');
}
if (configuration is BooksSettingsPath) {
return RouteInformation(location: '/settings');
}
if (configuration is BooksDetailsPath) {
return RouteInformation(location: '/book/${configuration.id}');
}
return null;
}
}
///
// Delegate route
///
class BookRouterDelegate extends RouterDelegate<BookRoutePath>
with ChangeNotifier, PopNavigatorRouterDelegateMixin<BookRoutePath> {
final GlobalKey<NavigatorState> navigatorKey;
//New app state
BookAppState appState = BookAppState();
//Constructor (to search)
BookRouterDelegate() : navigatorKey = GlobalKey<NavigatorState>() {
appState.addListener(notifyListeners);
}
//To search
@override
BookRoutePath get currentConfiguration {
if (appState.selectedPageIndex == 1) {
return BooksSettingsPath();
} else {
if (appState.selectedBook == null) {
return BooksListPath();
} else {
return BooksDetailsPath(appState.getSelectedBookById());
}
}
}
@override
Widget build(BuildContext context) {
return Navigator(
key: navigatorKey,
pages: [
MaterialPage(child: AppShell(appState: appState)),
],
onPopPage: (route, result) {
return route.didPop(result);
},
);
}
@override
Future<void> setNewRoutePath(BookRoutePath configuration) async {
if (configuration is BooksListPath) {
appState.selectedPageIndex = 0;
appState.selectedBook = null;
} else if (configuration is BooksSettingsPath) {
appState.selectedPageIndex = 1;
} else if (configuration is BooksDetailsPath) {
appState.selectedPageIndex = 0;
appState.setSelectedBookById(configuration.id);
}
}
}
//Routes
abstract class BookRoutePath {}
class BooksListPath extends BookRoutePath {}
class BooksSettingsPath extends BookRoutePath {}
class BooksDetailsPath extends BookRoutePath {
final int id;
BooksDetailsPath(this.id);
}
//Pages widget that contains
class AppShell extends StatefulWidget {
final BookAppState appState;
AppShell({@required this.appState});
@override
_AppShellState createState() => _AppShellState();
}
class _AppShellState extends State<AppShell> {
InnerRouterDelegate _routerDelegate;
ChildBackButtonDispatcher _backButtonDispatcher;
void initState() {
super.initState();
_routerDelegate = InnerRouterDelegate(widget.appState);
}
//TODO: search
@override
void didUpdateWidget(covariant oldWidget) {
super.didUpdateWidget(oldWidget);
_routerDelegate.appState = widget.appState;
}
// TODO: search
@override
void didChangeDependencies() {
super.didChangeDependencies();
// Defer back button dispatching to the child router
_backButtonDispatcher = Router.of(context)
.backButtonDispatcher
.createChildBackButtonDispatcher();
}
@override
Widget build(BuildContext context) {
var appState = widget.appState;
//Claim priority, If there are parallel sub router, you will need
//To pick which one should take priority;
_backButtonDispatcher.takePriority();
return Scaffold(
appBar: appState.selectedBook != null
? AppBar(
leading: IconButton(
icon: Icon(Icons.arrow_back),
onPressed: () => _routerDelegate.popRoute(),
),
actions: [
IconButton(
icon: Icon(Icons.more_vert),
onPressed: () => null,
)
],
)
: AppBar(),
body: Router(
routerDelegate: _routerDelegate,
backButtonDispatcher: _backButtonDispatcher,
),
bottomNavigationBar: BottomNavigationBar(
items: [
BottomNavigationBarItem(icon: Icon(Icons.home), label: 'Home'),
BottomNavigationBarItem(
icon: Icon(Icons.settings), label: 'Settings'),
],
currentIndex: appState.selectedPageIndex,
onTap: (newIndex) {
appState.selectedPageIndex = newIndex;
},
),
);
}
}
class InnerRouterDelegate extends RouterDelegate<BookRoutePath>
with ChangeNotifier, PopNavigatorRouterDelegateMixin<BookRoutePath> {
final navigatorKey = GlobalKey<NavigatorState>();
BookAppState _appState;
BookAppState get appState => _appState;
set appState(BookAppState value) {
if (value == _appState) {
return;
}
_appState = value;
notifyListeners();
}
InnerRouterDelegate(this._appState);
@override
Widget build(BuildContext context) {
return Navigator(
key: navigatorKey,
pages: [
if (appState.selectedPageIndex == 0) ...[
FadeAnimationPage(
child: BookListScreen(
books: appState.books,
onTapped: _handleBookTapped,
),
key: ValueKey('BooksListPage'),
),
if (appState.selectedBook != null)
MaterialPage(
key: ValueKey(appState.selectedBook),
child: BookDetailsScreen(
book: appState.selectedBook,
),
),
] else
FadeAnimationPage(
key: ValueKey('SettingsPage'),
child: SettingsScreen(),
)
],
onPopPage: (route, result) {
appState.selectedBook = null;
notifyListeners();
return route.didPop(result);
},
);
}
@override
Future<void> setNewRoutePath(BookRoutePath configuration) {
//Don't need to be implemented, Because Parent already delegates URI
// TODO: implement setNewRoutePath
throw UnimplementedError();
}
void _handleBookTapped(Book book) {
appState.selectedBook = book;
notifyListeners();
}
}
////
// Pages and screens
///
class FadeAnimationPage extends Page {
final Widget child;
FadeAnimationPage({Key key, this.child}) : super(key: key);
@override
Route createRoute(BuildContext context) {
return PageRouteBuilder(
settings: this,
pageBuilder: (context, animation, animation2) {
var curveTween = CurveTween(curve: Curves.easeIn);
return FadeTransition(
opacity: animation.drive(curveTween),
child: child,
);
});
}
}
class BookListScreen extends StatelessWidget {
final List<Book> books;
final ValueChanged<Book> onTapped;
const BookListScreen({@required this.books, @required this.onTapped});
@override
Widget build(BuildContext context) {
return Scaffold(
body: ListView.separated(
itemCount: books.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(books[index].title),
subtitle: Text(books[index].author),
onTap: () => onTapped(books[index]),
);
},
separatorBuilder: (context, index) => Divider(),
),
);
}
}
class BookDetailsScreen extends StatelessWidget {
final Book book;
const BookDetailsScreen({Key key, @required this.book}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: Padding(
padding: const EdgeInsets.all(8),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
if (book != null) ...[
Text(book.title, style: Theme.of(context).textTheme.headline6),
Text(book.author, style: Theme.of(context).textTheme.subtitle1),
]
],
),
),
);
}
}
class SettingsScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Text('Settings'),
),
);
}
}
//TODO: Edit screen
class BookEditScreen extends StatelessWidget {
final Book book;
const BookEditScreen({Key key, this.book}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: Padding(
padding: const EdgeInsets.all(8),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
if (book != null) ...[
Text(book.title, style: Theme.of(context).textTheme.headline6),
Text(book.author, style: Theme.of(context).textTheme.subtitle1),
]
],
),
),
);
}
}
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