katana_router_builder 1.7.0

Building system for katana router packages. Automatic Page route generation.

Katana Router

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Motivation

Flutter's Routing and Navigator are easy to use, and you can take advantage of great packages like go_router and auto_route, but each has some inconveniences.

• Deep linking cannot be used if routing is done using the push method or other methods in the Route class.
• If you use deep linking (e.g. pushNamed), you need to write the routing path directly as a String. It is also necessary to know the parameters in advance.
• Ability to redirect (e.g. AuthGuard) to the condition source.
• After creating the widget for a page, it is necessary to add the settings for routing, which requires editing two Dart files to create one page.

Therefore, I created a package with Generator that even creates files for routing just by adding Annotation to the Widget for the page.

This package has the following features

• Deep linking available.
  • Deep linking parameters available.
• Navigation and parameters are available in type safe.
• Widget can be used as is.
• Widgets can be used as pages with a small number of lines.
• All pages defined in the application can be understood and router classes can be automatically created.

This package can implement routing configuration as shown in the example below.

Create Page

// home.dart

import 'package:katana_router/katana_router.dart';
import 'package:flutter/material.dart';

part 'home.page.dart';

@PagePath("/")
class HomePage extends StatelessWidget {
  const HomePage();

  @pageRouteQuery
  static const query = _$HomePage();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Home")),
      body: Center(
        child: Text("Home page"),
      ),
    );
  }
}

Router Creation

// main.dart

import 'package:katana_router/katana_router.dart';
import 'package:flutter/material.dart';

import 'main.router.dart';

@appRoute
final appRouter = AppRouter();

void main() {
  runApp(const MainPage());
}

class MainPage extends StatelessWidget {
  const MainPage();

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      routerConfig: appRouter,
      title: "Test App",
    );
  }
}

Navigation

context.router.push(HomePage.query());

Installation

Import the following package for code generation using build_runner.

flutter pub add katana_router
flutter pub add --dev build_runner
flutter pub add --dev katana_router_builder

Implementation

Create Page

Widget to display by page path/user/any user ID is implemented as follows.

part 'original filename.page.dart'; to import a Part file.

Define the Widget as a page in @PagePath("path name") Annotation.

You can create a query for page transitions by defining a query field by giving @pageRouteQuery annotation.

Widget parameters can be defined as is.

// user.dart

import 'package:katana_router/katana_router.dart';
import 'package:flutter/material.dart';

part 'user.page.dart';

@PagePath("/user/:user_id")
class UserPage extends StatelessWidget {
  const UserPage({
    @PageParam("user_id") required this.userId,
    super.key,
  });

  final String userId;

  @pageRouteQuery
  static const query = _$UserPage();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("User")),
      body: Center(
        child: Text("User id: $userId"),
      ),
    );
  }
}

Router Creation

To create a router, grant @appRoute Annotation with a top-level value.

import 'original filename.router.dart'; to import library files.

Also, put the AppRouter object in its value.

Give that value directly to the routerConfig in MaterialApp.router. This will automatically pass the routing information to the application.

// main.dart

import 'package:katana_router/katana_router.dart';
import 'package:flutter/material.dart';

import 'main.router.dart';

@appRoute
final appRouter = AppRouter();

void main() {
  runApp(const MainPage());
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      routerConfig: appRouter,
      title: "Test App",
    );
  }
}

Navigation

To navigate to HomePage, do the following

The parameters defined in the widget can be described in the query as they are.

context.router.push(UserPage.query(userId: "User id"));

Code Generation

Automatic code generation is performed by entering the following command.

flutter pub run build_runner build --delete-conflicting-outputs

Additional Usage

Redirect

For example, use RedirectQuery to display the login screen if you are not logged in, and the home page if you are logged in.

Implement methods of redirect by inheriting from RedirectQuery.

The original RouteQuery is passed to source, so if the transition is to the page you are trying to transition to, return source as is.

If you want to transition to another page, pass a RouteQuery for that page.

import 'package:katana_router/katana_router.dart';
import 'dart:async';

class LoginRequiredRedirectQuery extends RedirectQuery {
  const LoginRequiredRedirectQuery();
  @override
  FutureOr<RouteQuery?> redirect(
      BuildContext context, RouteQuery source) async {
    if (isSignedIn) {
      return source;
    } else {
      return Login.query();
    }
  }
}

Page when the application is launched

It is possible to define a splash page when launching the application.

This splash page can be used to perform the first data load and other processes necessary to launch the application.

Create a class inheriting from BootRouteQueryBuilder and define onInit (processing at startup), build (screen display at startup), and initialTransitionQuery (transition from the startup screen to the first page).

import 'package:katana_router/katana_router.dart';
import 'package:flutter/material.dart';

class AppBoot extends BootRouteQueryBuilder {
  const AppBoot();

  @override
  Future<void> onInit(BuildContext context) async {
    await Future.delayed(const Duration(milliseconds: 1000));
  }

  @override
  Widget build(BuildContext context) {
    return Stack(
      fit: StackFit.expand,
      children: const [
        Material(child: AppLogo()),
        CompanyLogo(),
      ],
    );
  }

  @override
	TransitionQuery get initialTransitionQuery => TransitionQuery.fade;
}

The AppBoot class defined here is given as an argument in the AppRouter() class.

@appRoute
final appRouter = AppRouter(
	boot: const AppBoot(),
);

vs auto_route

There is a great existing package called auto_route that is a routing package that uses build_runner.

We will make a comparison with this package.

	katana_router	auto_route
How to describe routing	Annotation directly in Widget. Distributed definition.	Create a Router and list everything in Annotation. Concentrate and define.
Generated file	One per page + One per router	One with a router.
Type safe	○	○
Deep link	○	○
Deep Link Parameters	○	○
Redirect	○	○
Nested Navigation	scheduled for mounting	○