Introduction to the course, prerequisites, and goals

About this course

Introduction

About Module 2

Overview of the technology used in this course

About Flutter and Dart

Everything you need to start building Flutter apps

Hardware & software setup

\`flutter create\` and the Flutter project structure

Creating a Flutter app

How to build your app for emulators and physical devices

Running your app

Integrating external packages and libraries

Pub packages

Setting the app name, icon, and bundle ID

Packaging for the App Store and Google Play

Setting up your environment and packaging apps

Getting Started

About Module 3

A 5-minute introduction to the Dart language

Dart cheat sheet

Flutter in a nutshell

Setup: State

Setup: Theming

Setup: Navigation

Setup: Scaffold

Learn the basics you need to build any kind of app

Creating A Seed App

About Module 4

Text, app bar actions, and widgets that wrap every page

Creating the widget and route

Stubbing data

Widgets that wait for data

Column, Row, Padding, spacing, and alignment

Layout basics

Image

Table layouts, expansion panels, and rich text

Responsive layouts, part 2

ListView, SingleChildScrollView, and Scrollbar

Scrolling layouts

How to think about layout, infinite constraints, and unbounded size

Layout problems

TextButton, OutlinedButton, FilledButton, ElevatedButton, and button styles

Buttons

The Profile Page

About Module 5

VoiceOver on iOS

Testing accessibility on an Android emulator

TalkBack on Android

Accessibility Widgets

Making sure your app works with a screen reader

Accessibility

About Module 6

Shared preferences

HTTP requests

Login and authentication

State management with Provider and Consumer

Managing user state

Storage and HTTP

About Module 7

Building and sorting a DataTable with DataTableSource

Data tables

Using fl_chart for responsive visualizations

Charts and graphs

Building data visualizations that impress

Tables and Charts

About Module 8

Simple animations

Custom paint

Custom animations

Off-the-shelf transitions, custom drawings, and fine-tuned animations

Animations

About Module 9

flutter_test and the Flutter unit testing API

Unit tests

Testing UI interactions on individual widgets

Widget tests

Testing your entire app with automated interactions

End-to-end tests

Unit tests, widget tests, and end-to-end tests

Testing

Congratulations

Wrapping up

Flutter is a popular cross-platform development framework. It's packed with off-the-shelf features and focused
on developer ergonomics, which means you can build faster and deploy to more platforms with fewer dependencies.
Some parts of the framework will catch you by surprise, though, especially if you're used to developing for the
web or writing native apps. This course will walk you through the creation of a Flutter app from setup to
final package and help you develop a mental model that will carry you through the most common problems Flutter
devs encounter.

By the end of these 10 modules you'll have built:
- A Flutter seed project that can manage state, swap out color palettes, and handle deep links
- An accessible, error-resistant profile page that fetches data from a web API
- A responsive data table and data-driven visualizations
- A complete app ready to deploy to iPhone and Android

This course includes sample code, explained step-by-step, that you can reuse for any Flutter app you build.

It's taught by Isaac Lyman, author of _Your First Year in Code_ and Top 10 Author on The DEV Community.

After completing Line-of-Business Apps with Flutter 3, developers have the skills to build mobile apps backed by their
choice of server technologies, taking advantage of the incomparable performance, speed-to-value, and developer
experience of Flutter and Dart.

What developers are saying

Flutter

Dart

Bring your mobile app ideas to life on every device

### Build Better Mobile Apps with Flutter

Smartphones are the most popular computing devices in the world, and mobile apps are the best way to reach
technology consumers. But building fully native apps means learning two or more completely different sets of
programming languages, UI frameworks, layout systems, and developer toolkits. Other cross-platform frameworks
have tried to make this process easier, but none of them have achieved the popularity, performance, or resilience
of Flutter.

With Flutter, you'll avoid several problems you may have had with other app frameworks:

- Publish native app packages for iOS, Android, Windows, macOS, and Linux, all from a **single codebase**, without
writing a single line of native code.
- Write **faster, safer code** with the familiar syntax, type safety, and null safety of the Dart programming language.
- Flutter is an **all-in-one component library and toolkit**: spend your time building components and writing application logic
instead of fiddling with toolchain configuration and searching for 3rd-party packages.
- Never worry about the way your app looks on different devices; with Flutter's **built-in rendering engine**
and **logical pixel scaling**, your app will look the same on every screen, everywhere.

### Be Prepared for Any Challenge

Flutter is an easy-to-learn, top-rated technology for developers, but it doesn't come without gotchas. In this course, you'll
learn to breeze right through some of the hardest parts of Flutter development:

- Responsive design, complex layouts, and breakpoints
- Layout errors and infinite constraints
- Hand-drawn components
- Custom animations, tickers, and tweens
- State management and data persistence

### Start Building Real Apps Faster

This course won't waste any time teaching you what an `if` statement is. You'll be able to use the
programming experience you already have and jump straight into building mobile apps with Dart and Flutter.

Along the way, you'll build skills you can use immediately for any app you dream up:

- By the end of Module 2, you'll have already packaged a Flutter app for distribution on the iOS and Android
app stores.
- By the end of Module 3, you'll have a seed app you can use for any project.
- By the end of Module 4, you'll know how to build responsive layouts and use the most common types of widgets.
- By the end of the course, you'll have built an **accessible**, **interactive**, **server-backed** app with **custom animations**
and **three types of automated tests**.

Along the way, you'll discover Flutter's secret: it's not only the easiest way to build cross-platform mobile
and desktop apps, it's the easiest way to deliver **any* kind of technological experience, **period**. Not even the web, with
its variety of frameworks and tools, can match the development speed and polished UI of a Flutter app.

Build cross-platform iOS and Android apps faster than you thought possible

In this course you'll build a corporate app and package it for iPhone and Android from a single codebase.

Flutter is a popular and feature-rich multi-platform development toolkit, but it's got some surprises for
traditional web and desktop developers. You'll learn how to think in the Flutter way and build fast, maintainable,
visually appealing apps.

Line-of-Business Mobile Apps with Flutter and Dart

Build a secure login modal with HTTP authentication and persistent cookies

Build responsive, nested layouts and intuitive user interactions

Build fast, informative data visualizations

How to build and package apps for iOS and Android from a single codebase

Why Flutter and Dart are a perfect match for multi-platform apps

The Flutter paradigm for layout and components

How to keep your Flutter app fast and responsive

State management, server requests, accessibility, and more

 page where you can see who you're logged in as and manage your data. Let's build one now. Start up Revenue Explorer on whatever device or simulator you prefer so you can see what's changing as you go along.

Begin by building a widget (everything in Flutter is a widget). Create a new folder, 

 (these are based on personal preference, not some routing-by-convention scheme; use whatever folder and file names you like). Then, create a class that extends 

class RevExProfilePage extends StatelessWidget {}

By this point, you may be wondering why I prefix all public identifiers with 

. It's short for Revenue Explorer, and I like using prefixes on everything that comes from the project itself (as opposed to a third-party package), so I know whether it's "mine" or "someone else's" just by looking at it. If you don't like that convention, you can name things however you want.

import 'package:flutter/material.dart';

class RevExProfilePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    throw UnimplementedError();
  }
}

Sweet, a widget. All it does so far is throw an error, but that will be fixed soon.

You may notice there's still a warning underline and a light bulb 💡 on 

. If you want to click the suggestion to get rid of the underline, go for it. You'll get this:

import 'package:flutter/material.dart';

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

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    throw UnimplementedError();
  }
}

Now you have an explicit constructor that accepts a 

 parameter and passes it to the super constructor (which comes from 

). It's a named parameter and doesn't have the 

 keyword, so it's optional—you can construct your widget without it, no problem. So you're not making any trouble for yourself by leaving it there, even though you won't use it most of the time.

 do? If you've done any web development with React, Angular, or Vue, you'll recognize the term from your list templates.

If the same stateful widget appears multiple times in a list

 and you plan on rearranging that list at runtime, the 

 parameter helps Flutter track which widget is which, regardless of its position.

In some advanced cases, you can also use a 

 to access a widget's context and state from somewhere else in the widget tree. Assuming you have some kind of state management solution, you won't need to do this very often (or at all). But it's good to be aware of anyway.

 is one of the most common widgets in Flutter. It displays text. It does almost everything you'd expect a piece of text to be able to do: use a specific font or color or font size with the 

 parameter, overflow onto multiple lines with the 

 parameter, control its own alignment with the 

 widget from your profile page. You can change it later, but for now, you're just trying to make sure the page shows up when it's supposed to.

import 'package:flutter/material.dart';

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

  @override
  Widget build(BuildContext context) {
    return const Text(
      "Profile page works!",
    );
  }
}

Now you have a page that theoretically renders something. Let's make a route for it.

final revexRouter = GoRouter(routes: <GoRoute>[
  GoRoute(
    path: '/',
    redirect: (_, __) => '/home',
  ),
  GoRoute(
    path: '/home',
    pageBuilder: (context, state) => const MaterialPage(
      child: MyHomePage(title: 'Flutter Demo Home Page'),
    ),
  ),
  GoRoute(
    path: '/profile',
    pageBuilder: (context, state) => const MaterialPage(
      child: RevExProfilePage(),
    ),
  ),
]);

 library. Here, its purpose is to define the animation for when you switch pages: on Android, you'll get a fade effect, and on iOS, you'll get a fly-in effect.

---
title: Creating the widget and route
description: Text, app bar actions, and widgets that wrap every page
privateVideoUrl: 
isPublicLesson: true
code: https://gitlab.com/fullstackio/books/newline-course-apps/isaac-lyman-line-of-business-apps-with-flutter-3/-/tree/main/App/revenue_explorer_complete_app
---

Most apps have a **Profile** page where you can see who you're logged in as and manage your data. Let's build one now. Start up Revenue Explorer on whatever device or simulator you prefer so you can see what's changing as you go along.

## Profile widget

Begin by building a widget (everything in Flutter is a widget). Create a new folder, `lib/pages`, and a file at `lib/pages/profile.page.dart` (these are based on personal preference, not some routing-by-convention scheme; use whatever folder and file names you like). Then, create a class that extends `StatelessWidget`.

```dart
class RevExProfilePage extends StatelessWidget {}
```

:::info

By this point, you may be wondering why I prefix all public identifiers with `RevEx`. It's short for Revenue Explorer, and I like using prefixes on everything that comes from the project itself (as opposed to a third-party package), so I know whether it's "mine" or "someone else's" just by looking at it. If you don't like that convention, you can name things however you want.

:::

Your IDE will do two things here.

1.  It will show a light bulb 💡 on `StatelessWidget` to offer some imports. You'll want to pick the option that says **Import library 'package:flutter/material.dart'**, since you're using Material Design components.
2.  It will show a light bulb 💡 on `RevExProfilePage`. Click it and choose **Create 1 missing override**. This will implement your `build` method.

Now you should have something like this:

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

class RevExProfilePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    throw UnimplementedError();
  }
}
```

Sweet, a widget. All it does so far is throw an error, but that will be fixed soon.

## Widget keys

You may notice there's still a warning underline and a light bulb 💡 on `RevExProfilePage`. The IDE suggests that you **Add 'key' to constructors**. If you want to click the suggestion to get rid of the underline, go for it. You'll get this:

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

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

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    throw UnimplementedError();
  }
}
```

Now you have an explicit constructor that accepts a `key` parameter and passes it to the super constructor (which comes from `StatelessWidget`). It's a named parameter and doesn't have the `required` keyword, so it's optional—you can construct your widget without it, no problem. So you're not making any trouble for yourself by leaving it there, even though you won't use it most of the time.

What does `super.key` do? If you've done any web development with React, Angular, or Vue, you'll recognize the term from your list templates.

_If the same stateful widget appears multiple times in a list_ and you plan on rearranging that list at runtime, the `key` parameter helps Flutter track which widget is which, regardless of its position.

In some advanced cases, you can also use a `key` to access a widget's context and state from somewhere else in the widget tree. Assuming you have some kind of state management solution, you won't need to do this very often (or at all). But it's good to be aware of anyway.

## Text

Okay, time to replace that `UnimplementedError`.

[`Text`](https://api.flutter.dev/flutter/widgets/Text-class.html) is one of the most common widgets in Flutter. It displays text. It does almost everything you'd expect a piece of text to be able to do: use a specific font or color or font size with the `style` parameter, overflow onto multiple lines with the `maxLines` parameter, control its own alignment with the `textAlign` parameter, and so on.

For now, return a `Text` widget from your profile page. You can change it later, but for now, you're just trying to make sure the page shows up when it's supposed to.

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

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

  @override
  Widget build(BuildContext context) {
    return const Text(
      "Profile page works!",
    );
  }
}
```

A couple of things to note:

-   The `const` keyword is used to construct `Text` because, as you can see, there's no way for it to ever change. As it's currently coded, it will always just say, "Profile page works!" Flutter can render it once and then leave it alone forever. Rendering a StatelessWidget with `const` is pretty much the most efficient and performant thing you can possibly do. (Your IDE will tell you when you should use `const`, so don't worry about figuring it out on your own.)
-   There's a trailing comma in the `Text` constructor arguments. Dart doesn't mind at all, and the Dart auto-formatter will take that as a cue to put each argument on its own line. Trailing commas can go almost anywhere (one big exception being trailing initializer statements on a class constructor). You can use 'em as much or as little as you like.

Now you have a page that theoretically renders something. Let's make a route for it.

## Profile GoRoute

Open your `router.dart` file and add a `GoRoute` that renders your page:

```dart
final revexRouter = GoRouter(routes: <GoRoute>[
  GoRoute(
    path: '/',
    redirect: (_, __) => '/home',
  ),
  GoRoute(
    path: '/home',
    pageBuilder: (context, state) => const MaterialPage(
      child: MyHomePage(title: 'Flutter Demo Home Page'),
    ),
  ),
  GoRoute(
    path: '/profile',
    pageBuilder: (context, state) => const MaterialPage(
      child: RevExProfilePage(),
    ),
  ),
]);
```

[`MaterialPage`](https://api.flutter.dev/flutter/material/MaterialPage-class.html) is, surprisingly, not a widget. It's a `Page`, part of Flutter's internal `Navigator` library. Here, its purpose is to define the animation for when you switch pages: on Android, you'll get a fade effect, and on iOS, you'll get a fly-in effect.