Imported from Thomas032/mobile-app-development-group-7-portfolio (cal_tab/.agents/skills/flutter-setup-declarative-routing/SKILL.md). Install upstream with npx skills add Thomas032/mobile-app-development-group-7-portfolio --skill flutter-setup-declarative-routing. Copyright stays with the author.

Implementing Routing and Deep Linking

Contents

• Core Concepts
• Workflow: Initializing the Application and Router
• Workflow: Configuring Platform Deep Linking
• Workflow: Implementing Nested Navigation
• Examples

Core Concepts

Use the go_router package for declarative routing in Flutter. It provides a robust API for complex routing scenarios, deep linking, and nested navigation.

• GoRouter: The central configuration object defining the application's route tree.
• GoRoute: A standard route mapping a URL path to a Flutter screen.
• ShellRoute / StatefulShellRoute: Wraps child routes in a persistent UI shell (e.g., a BottomNavigationBar). StatefulShellRoute maintains the state of parallel navigation branches.
• Path URL Strategy: Removes the default # fragment from web URLs, essential for clean deep linking across platforms.

Workflow: Initializing the Application and Router

Follow this workflow to bootstrap a new Flutter application with go_router and configure the root routing mechanism.

Task Progress

• Create the Flutter application.
• Add the go_router dependency.
• Configure the URL strategy for web/deep linking.
• Implement the GoRouter configuration.
• Bind the router to MaterialApp.router.

1. Scaffold the Application

Run the following commands to create the app and add the required routing package:

flutter create <app-name>
cd <app-name>
flutter pub add go_router

2. Configure the Router

Define a top-level GoRouter instance. Handle authentication or state-based routing using the redirect parameter.

import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';
import 'package:flutter_web_plugins/url_strategy.dart';

void main() {
  // Use path URL strategy to remove the '#' from web URLs
  usePathUrlStrategy();
  runApp(const MyApp());
}

final GoRouter _router = GoRouter(
  initialLocation: '/',
  routes: [
    GoRoute(
      path: '/',
      builder: (context, state) => const HomeScreen(),
      routes: [
        GoRoute(
          path: 'details/:id',
          builder: (context, state) => DetailsScreen(id: state.pathParameters['id']!),
        ),
      ],
    ),
  ],
  errorBuilder: (context, state) => ErrorScreen(error: state.error),
);

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      routerConfig: _router,
      title: 'Routing App',
    );
  }
}

Workflow: Configuring Platform Deep Linking

Configure the native platforms to intercept specific URLs and route them into the Flutter application.

Task Progress

• Determine target platforms (iOS, Android, or both).
• Apply conditional configuration for Android (Manifest + Asset Links).
• Apply conditional configuration for iOS (Plist + Entitlements + AASA).
• Run validator -> review errors -> fix.

If configuring for Android:

1. Modify AndroidManifest.xml: Add the intent filter inside the <activity> tag for .MainActivity.

<intent-filter android:autoVerify="true">
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.DEFAULT" />
    <category android:name="android.intent.category.BROWSABLE" />
    <data android:scheme="http" android:host="yourdomain.com" />
    <data android:scheme="https" />
</intent-filter>

2. Host assetlinks.json: Serve the following JSON at https://yourdomain.com/.well-known/assetlinks.json.

[{
  "relation": ["delegate_permission/common.handle_all_urls"],
  "target": {
    "namespace": "android_app",
    "package_name": "com.yourcompany.yourapp",
    "sha256_cert_fingerprints": ["YOUR_SHA256_FINGERPRINT"]
  }
}]

If configuring for iOS:

1. Modify Info.plist: Opt-in to Flutter's default deep link handler. Note: If using a third-party deep linking plugin (e.g., app_links), set this to NO to prevent conflicts.

<key>FlutterDeepLinkingEnabled</key>
<true/>

2. Modify Runner.entitlements: Add the associated domain.

<key>com.apple.developer.associated-domains</key>
<array>
  <string>applinks:yourdomain.com</string>
</array>

3. Host apple-app-site-association: Serve the following JSON (without a .json extension) at https://yourdomain.com/.well-known/apple-app-site-association.

{
  "applinks": {
    "apps": [],
    "details": [{
      "appIDs": ["TEAM_ID.com.yourcompany.yourapp"],
      "paths": ["*"],
      "components": [{"/": "/*"}]
    }]
  }
}

Validation Loop

Run validator -> review errors -> fix.

• Android: Test using ADB.

  adb shell 'am start -a android.intent.action.VIEW -c android.intent.category.BROWSABLE -d "https://yourdomain.com/details/123"' com.yourcompany.yourapp

• iOS: Test using xcrun on a booted simulator.

  xcrun simctl openurl booted https://yourdomain.com/details/123

Workflow: Implementing Nested Navigation

Use StatefulShellRoute to implement persistent UI shells (like a bottom navigation bar) that maintain the state of their child routes.

Task Progress

• Define StatefulShellRoute.indexedStack in the GoRouter configuration.
• Create StatefulShellBranch instances for each navigation tab.
• Implement the shell widget using StatefulNavigationShell.

final GoRouter _router = GoRouter(
  initialLocation: '/home',
  routes: [
    StatefulShellRoute.indexedStack(
      builder: (context, state, navigationShell) {
        return ScaffoldWithNavBar(navigationShell: navigationShell);
      },
      branches: [
        StatefulShellBranch(
          routes: [
            GoRoute(
              path: '/home',
              builder: (context, state) => const HomeScreen(),
            ),
          ],
        ),
        StatefulShellBranch(
          routes: [
            GoRoute(
              path: '/settings',
              builder: (context, state) => const SettingsScreen(),
            ),
          ],
        ),
      ],
    ),
  ],
);

Examples

High-Fidelity Shell Widget Implementation

Implement the UI shell that consumes the StatefulNavigationShell to handle branch switching.

class ScaffoldWithNavBar extends StatelessWidget {
  const ScaffoldWithNavBar({
    required this.navigationShell,
    super.key,
  });

  final StatefulNavigationShell navigationShell;

  void _goBranch(int index) {
    navigationShell.goBranch(
      index,
      // Support navigating to the initial location when tapping the active tab.
      initialLocation: index == navigationShell.currentIndex,
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: navigationShell,
      bottomNavigationBar: NavigationBar(
        selectedIndex: navigationShell.currentIndex,
        onDestinationSelected: _goBranch,
        destinations: const [
          NavigationDestination(icon: Icon(Icons.home), label: 'Home'),
          NavigationDestination(icon: Icon(Icons.settings), label: 'Settings'),
        ],
      ),
    );
  }
}

Programmatic Navigation

Use the context.go() and context.push() extension methods provided by go_router.

// Replaces the current route stack with the target route (Declarative)
context.go('/details/123');

// Pushes the target route onto the existing stack (Imperative)
context.push('/details/123');

// Navigates using a named route and path parameters
context.goNamed('details', pathParameters: {'id': '123'});

// Pops the current route
context.pop();