# Building a Yaru app with Flutter ||| |---|---| |**Summary**|| |**URL**|https://github.com/ubuntu/user_manager| |**Category**|| |**Environment**|Linux| |**Status**|| |**Feedback Link**|| |**Author**|Frederik Feichtmeier| ____ # Introduction ## What you'll learn - Setting up a Flutter development environment in Ubuntu - Building a Flutter app for the Linux desktop, using the [yaru theme](https://github.com/ubuntu/yaru.dart) - Using [json-server](https://github.com/typicode/json-server) as a local backend to store data ## What you'll build ![](.github/09_final_app_dark.png) ____ # Set up your Flutter environment ## Install Flutter on Ubuntu and enable flutter Linux desktop support ```bash sudo snap install flutter --classic flutter channel beta flutter upgrade flutter config --enable-linux-desktop ``` ## Install and setup Visual Studio Code To install VS Code in Ubuntu fire up a terminal and run the following command: ```bash sudo snap install code --classic ``` Launch VS Code Quick Open (Ctrl+P), paste the following command ... ``` ext install Dart-Code.flutter ``` ... and press enter to install [the official Flutter VS Code extension](https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter). # Get started Open a terminal or the VS Code integrated terminal and run the following command to create a new flutter project for the fictional organization `org.flutterfans` ```bash flutter create --org org.flutterfans user_manager ``` Open the project directory `user_manager` you've just created with VS Code. ![](.github/00_open.png) You should now see the following directories (1) and the "Linux (linux-x64)" (2) device in use, which is the default on Linux after you've enabled the linux desktop support: ![directory_overview](.github/01_directory_overview.png) Let's make a small test if the application launches, by opening the `lib` directory (1) and clicking on the small `Run` label above `void main()` (2) ![](.github/02_first_launch.png) ## Using the Yaru theme Open `pubspec.yaml` - the file for managing of the lifecycle of your app - and add `yaru: ^0.0.6` under the dependencies section, so you end up with the following dependencies (check that `yaru` is on the same column as `flutter`): ```yaml dependencies: flutter: sdk: flutter yaru: ^0.0.6 ``` You can now import the yaru theme by adding ```dart import 'package:yaru/yaru.dart' as yaru; ``` at the top of `main.dart`. Use the yaru theme in your app by setting the `theme` property of `MaterialApp` to `yaru.lightTheme` and the `darkTheme` property to `yaru.darkTheme` so you end up with the following class definition - your app now follows your system's theme. ```dart class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( title: 'Flutter Demo', theme: yaru.lightTheme, darkTheme: yaru.darkTheme, home: MyHomePage(title: 'Flutter Demo Home Page'), ); } } ``` ![](.github/04_toggle_themes.gif) # Building the app ## Organize your project structure You might want to organize your project's directory structure a little bit. Start by creating a `view` directory under `lib` by right-clicking the `lib` directory and click the `New folder` menu entry and type in `view` into the textfield that pops out. ![](.github/05_create_view_dir.png) Repeat this step with a `model` and a `service` directory to end up with the following directory tree above `main.dart`: ![](.github/06_project_structure.png) ## A simple user model To easily send user data across your app and to the server you want to have a user class, containing only the data properties of your user. Right-click on the `model` directory and click on `New file` and name it `user.dart`: ![](.github/07_new_file.png) Insert the following code ```dart class User { int? id; String name; User({required this.id, required this.name}); User.empty() : this(id: null, name: ""); factory User.fromJson(Map json) => User(id: json['id'], name: json['name']); Map toJson() => {"id": id, "name": name}; } ``` ## The user service To let your app communicate via HTTP with your server, add `http: ^0.13.1` in your `pubspec.yaml` under the `dependencies` section, create `user_service.dart` in the `service` directory and paste the following code into: ```dart import 'dart:convert'; import 'package:http/http.dart' as http; import 'package:user_manager/model/user.dart'; class UserService { UserService({required this.uri}); final String uri; Future> getUsers() async { final response = await http.get(Uri.http(uri, 'users')); if (response.statusCode == 200) { var usersJson = jsonDecode(response.body.toString()) as List; return usersJson.map((json) => User.fromJson(json)).toList(); } else { throw Exception(response.statusCode.toString() + ': ' + response.body); } } Future saveUser(User user) async { for (var aUser in await getUsers()) { if (aUser.id == user.id) { await updateUser(user); return; } } await addUser(user); } Future addUser(User user) async { return await http.post(Uri.http(uri, 'users'), headers: { 'Content-Type': 'application/json; charset=UTF-8', }, body: jsonEncode(user.toJson())); } Future updateUser(User user) async { return await http.put(Uri.http(uri, 'users/${user.id}'), headers: { 'Content-Type': 'application/json; charset=UTF-8', }, body: jsonEncode(user.toJson())); } Future removeUser(User user) async { await http.delete((Uri.http(uri, 'users/${user.id}'))); } } ``` ## The UI ### One card for each user Each user that will be managed is represented by a card inside the UI. Create `user_card.dart` in the `view` directory and paste in the following code ```dart import 'package:flutter/material.dart'; import 'package:user_manager/model/user.dart'; class UserCard extends StatefulWidget { final User user; final VoidCallback onDelete; final VoidCallback onEdit; UserCard({required this.user, required this.onDelete, required this.onEdit}); @override _UserCardState createState() => _UserCardState(); } class _UserCardState extends State { @override Widget build(BuildContext context) { return Card( child: Column( mainAxisSize: MainAxisSize.min, children: [ ListTile( leading: Icon(Icons.person), title: Text(widget.user.name), ), Row( mainAxisAlignment: MainAxisAlignment.end, children: [ TextButton( child: const Text('Edit'), onPressed: () => widget.onEdit(), ), const SizedBox(width: 8), TextButton( child: const Text('Remove'), onPressed: () => widget.onDelete(), ), const SizedBox(width: 8), ], ), ], ), ); } } ``` ### A dialog to edit users in A user will be edited inside a dialog, spawned from clicking on the either the big green floating action button or the edit button of your user card. Create the file `user_edit_dialog.dart` inside the `view` directory and copy/paste the following code into: ```dart import 'package:flutter/foundation.dart'; import 'package:flutter/material.dart'; import 'package:flutter/widgets.dart'; class UserEditDialog extends StatefulWidget { final TextEditingController nameController; final AsyncCallback editUser; UserEditDialog({required this.nameController, required this.editUser}); @override _UserEditDialogState createState() => _UserEditDialogState(); } class _UserEditDialogState extends State { @override Widget build(BuildContext context) { return Dialog( child: Container( height: 150, width: 200, child: Padding( padding: const EdgeInsets.all(10.0), child: Column( mainAxisAlignment: MainAxisAlignment.start, crossAxisAlignment: CrossAxisAlignment.start, children: [ Padding( padding: const EdgeInsets.all(8.0), child: TextField( autofocus: true, controller: widget.nameController, decoration: InputDecoration(hintText: 'User name'), ), ), Row( children: [ Padding( padding: const EdgeInsets.all(8.0), child: ElevatedButton( onPressed: () async => Navigator.of(context).pop(widget.editUser()), child: Text( "Save", style: TextStyle(color: Colors.white), ), ), ), Padding( padding: const EdgeInsets.all(8.0), child: TextButton( onPressed: () => Navigator.of(context).pop(), child: Text("Cancel"), ), ) ], ), ], ), ), ), ); } } ``` ### The new home page The old home page won't be enough anymore so you need a new one to load the user cards into. The home page uses the user service to manage the user data. Open your `pubspec.yaml` file again and add `injector: ^2.0.0` in the `dependencies` section. Create the file `home_page.dart` in the `view` directory and paste the following code: ```dart import 'package:flutter/material.dart'; import 'package:flutter/widgets.dart'; import 'package:injector/injector.dart'; import 'package:user_manager/model/user.dart'; import 'package:user_manager/service/user_service.dart'; import 'package:user_manager/view/user_card.dart'; import 'package:user_manager/view/user_edit_dialog.dart'; class HomePage extends StatefulWidget { @override _HomePageState createState() => _HomePageState(); } class _HomePageState extends State { late TextEditingController _nameController; final _userService = Injector.appInstance.get(); @override void initState() { _nameController = TextEditingController(); super.initState(); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar( title: const Text('Home'), ), body: Center( child: Padding( padding: const EdgeInsets.all(8.0), child: Scrollbar( child: FutureBuilder( future: _userService.getUsers(), builder: (context, AsyncSnapshot> snapShot) { if (snapShot.hasData) { return ListView( children: snapShot.data! .map((user) => UserCard( user: user, onDelete: () { _userService .removeUser(user) .then((value) => setState(() { _showSnackBar( 'Deleted user: ' + user.name); })) .onError((error, stackTrace) => _showSnackBar(error.toString())); }, onEdit: () => editUser(user, context))) .toList(), ); } return CircularProgressIndicator(); }), ), ), ), floatingActionButton: FloatingActionButton( child: Icon(Icons.add), onPressed: () { _nameController.text = ""; editUser(new User.empty(), context); }, ), ); } void editUser(User user, BuildContext context) { _nameController.text = user.name; showDialog( context: context, barrierDismissible: false, builder: (BuildContext context) { return UserEditDialog( nameController: _nameController, editUser: () async { user.name = _nameController.text; _userService .saveUser(user) .then((value) => setState(() { _showSnackBar('Saved user: ' + user.name); })) .onError( (error, stackTrace) => _showSnackBar(error.toString())); }); }); } void _showSnackBar(String message) { ScaffoldMessenger.of(context).showSnackBar( SnackBar(duration: const Duration(seconds: 1), content: Text(message))); } } ``` ## Finish up your main.dart The UI of the test app is no longer needed. Remove all Widgets except `MyApp`, change the `home` property to `HomePage()`, change your `main()` function to by asynchronous, returning a `Future` and register your `UserService` with the `Injector` class before you run your app. To be sure you've imported everything correctly, replace all code inside `main.dart` with the following new version: ```dart import 'package:flutter/material.dart'; import 'package:injector/injector.dart'; import 'package:user_manager/service/user_service.dart'; import 'package:user_manager/view/home_page.dart'; import 'package:yaru/yaru.dart' as yaru; Future main() async { final userService = UserService(uri: 'localhost:3000'); Injector.appInstance.registerDependency(() => userService); runApp(MyApp()); } class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( title: 'Flutter Demo', theme: yaru.lightTheme, darkTheme: yaru.darkTheme, home: HomePage(), ); } } ``` ## Create a local server to process client requests ### Create mock data Create `db.json` inside the root folder of your application and insert some fictional users in the json format: ```json { "users": [ { "id": 1, "name": "Carlo" }, { "id": 2, "name": "Mads" }, { "id": 3, "name": "Frederik" }, { "id": 4, "name": "Stuart" }, { "id": 5, "name": "Paul" }, { "id": 6, "name": "Muq" } ] } ``` ### Install node-js and json-server We will use a [fantastic local mock server](https://github.com/typicode/json-server) to let our client talk to. To do so we need the [node snap](https://snapcraft.io/node). Enter the following commands to install node and json-server. ```bash sudo snap install node --classic sudo npm install -g json-server ``` # Entering the user management :) Start your json-server by running the following command ```bash json-server --watch db.json ``` Start your app again! Done :) You can now manage users inside a Ubuntu Linux app, using the yaru theme: ![](.github/08_final_app.png)

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