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

You're ready to build out the Profile page with realistic data. Here's a mock-up of what I have in mind:

At the highest level, the page will be a vertical list of widgets. Anytime you need a vertical (top to bottom) layout, start with the 

@override
Widget build(BuildContext context) {
  return RevExScaffold(
    title: "Profile",
    body: FutureBuilder(
      future: user,
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const CircularProgressIndicator();
        }

        if (snapshot.hasError) {
          return const Text('Error: Cannot get user data.');
        }

        final user = snapshot.data;

        return Column(
          children: const [],
        );
      },
    ),
  );
}

. You can add widgets to the list literal in the code above, or use a mapping function to create a list of widgets from an array of data. In this case, adding widgets directly will be easier.

I'm imagining the "Log Out" button as belonging to a fixed footer. The AppBar will be fixed in place as well. Everything else (profile image, contact info, client list) will be scrollable.

Create widgets to represent the two different parts of the page.

class _ProfileContent extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const Text('Profile Content');
  }
}

class _ProfileFixedFooter extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const Text('Profile Footer');
  }
}

The "RevEx" prefix isn't useful here because both of these class names start with an underscore, meaning they're private to the file. If you see something with an underscore, you know it came from the same file; you don't have to wonder who it belongs to.

You'll see a warning on each class because it isn't being used yet. Dart likes to let you know about unused private identifiers so you can delete them. Add them to the Column you constructed earlier:

@override
Widget build(BuildContext context) {
  return RevExScaffold(
    title: "Profile",
    body: FutureBuilder(
      future: user,
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const CircularProgressIndicator();
        }

        if (snapshot.hasError) {
          return const Text('Error: Cannot get user data.');
        }

        final user = snapshot.data;

        return Column(
          children: [
            _ProfileContent(),    // <= new Widgets added here
            _ProfileFixedFooter(),
          ],
        );
      },
    ),
  );
}

 on the list literal has been removed because neither of your widgets has a constant constructor right now (implicit constructors are never constant). It's very likely they will later, but you can let that happen when it happens.

If you run the app right now, you'll see that "Profile Content" and "Profile Footer" take up two lines just below the app bar. You want to change the 

 widget to take up all available vertical space in the viewport, except what's needed for the AppBar and fixed footer. Since the AppBar is higher up in the hierarchy, you don't need to worry about it here. But to negotiate space between the main content and the footer, you can use the 

, which is the generic version of both). It takes up as much free space as it can. If you use multiple 

 widgets, the free space will be shared equally between them. It's very similar to 

 doesn't have to be an immediate child of a 

—there can be other widgets in between, as long as they're all StatelessWidgets or StatefulWidgets. But be very careful about putting too much between them. If Flutter can't find the Row or Column intended as the parent, it will throw an error. In particular, 

avoid putting the Row/Column in one widget and the Expanded in another

—that makes it way too easy to use the latter without the former, causing a runtime error.

Update the RevExProfilePage build method as follows:

@override
Widget build(BuildContext context) {
  return RevExScaffold(
    title: "Profile",
    body: FutureBuilder(
      future: user,
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const CircularProgressIndicator();
        }

        if (snapshot.hasError) {
          return const Text('Error: Cannot get user data.');
        }

        final user = snapshot.data;

        return Column(
          children: [
            Expanded(      // <= Expanded added here
              child: _ProfileContent(),
            ),
            _ProfileFixedFooter(),
          ],
        );
      },
    ),
  );
}

To quickly wrap a widget with another widget (something you'll be doing a lot), click the widget you want to wrap and open the context actions. Then select 

 options. They name some of the most commonly used widgets in Flutter layouts. By the end of this course, you'll be familiar with all of them.

Depending on where you are in the layout, options like 

, which deletes the widget from the build method but leaves the rest of the hierarchy (parent and child widgets) intact, and 

, which swaps the widget with its immediate child, are also available. Using these context actions is much easier than trying to alter deeply nested widget trees by hand.

Now if you look at the app, "Profile Content" appears just below the app bar, and "Profile Footer" appears at the bottom of the screen.

It would be nice if "Profile Content" and "Profile Footer" weren't flush with the left side of the screen. In modern apps, people tend to prefer a lot of space around things. You can add a 

@override
Widget build(BuildContext context) {
  return RevExScaffold(
    title: "Profile",
    body: Padding(     // <= Padding added here
      padding: const EdgeInsets.symmetric(horizontal: 16),
      child: FutureBuilder(
        future: user,
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            return const CircularProgressIndicator();
          }

          if (snapshot.hasError) {
            return const Text('Error: Cannot get user data.');
          }

          final user = snapshot.data;

          return Column(
            children: [
              Expanded(
                child: _ProfileContent(),
              ),
              _ProfileFixedFooter(),
            ],
          );
        },
      ),
    ),
  );
}

---
title: Layout basics
description: Column, Row, Padding, spacing, and alignment 
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
---

You're ready to build out the Profile page with realistic data. Here's a mock-up of what I have in mind:

![Rough sketch of a page with a "Profile" header, a circular image with a name superimposed on it and a job title underneath, contact details, an expandable list of clients, and a Log Out button at the bottom](https://d2uusema5elisf.cloudfront.net/courses/line-of-business-mobile-apps-with-flutter-and-dart/module_04/lesson_04.05/public/assets/flutter-profile-mockup.png)

## Column

At the highest level, the page will be a vertical list of widgets. Anytime you need a vertical (top to bottom) layout, start with the [`Column`](https://api.flutter.dev/flutter/widgets/Column-class.html) widget.

Open `lib/pages/profile.page.dart` and replace the final `Text` with a `Column`, like so:

```dart
@override
Widget build(BuildContext context) {
  return RevExScaffold(
    title: "Profile",
    body: FutureBuilder(
      future: user,
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const CircularProgressIndicator();
        }

        if (snapshot.hasError) {
          return const Text('Error: Cannot get user data.');
        }

        final user = snapshot.data;

        return Column(
          children: const [],
        );
      },
    ),
  );
}
```

`Column` has a `children` field of type `List<Widget>`. You can add widgets to the list literal in the code above, or use a mapping function to create a list of widgets from an array of data. In this case, adding widgets directly will be easier.

I'm imagining the "Log Out" button as belonging to a fixed footer. The AppBar will be fixed in place as well. Everything else (profile image, contact info, client list) will be scrollable.

Create widgets to represent the two different parts of the page.

```dart
class _ProfileContent extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const Text('Profile Content');
  }
}

class _ProfileFixedFooter extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const Text('Profile Footer');
  }
}
```

:::info

The "RevEx" prefix isn't useful here because both of these class names start with an underscore, meaning they're private to the file. If you see something with an underscore, you know it came from the same file; you don't have to wonder who it belongs to.

:::

You'll see a warning on each class because it isn't being used yet. Dart likes to let you know about unused private identifiers so you can delete them. Add them to the Column you constructed earlier:

```dart
@override
Widget build(BuildContext context) {
  return RevExScaffold(
    title: "Profile",
    body: FutureBuilder(
      future: user,
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const CircularProgressIndicator();
        }

        if (snapshot.hasError) {
          return const Text('Error: Cannot get user data.');
        }

        final user = snapshot.data;

        return Column(
          children: [
            _ProfileContent(),    // <= new Widgets added here
            _ProfileFixedFooter(),
          ],
        );
      },
    ),
  );
}
```

The `const` on the list literal has been removed because neither of your widgets has a constant constructor right now (implicit constructors are never constant). It's very likely they will later, but you can let that happen when it happens.

## Expanded

If you run the app right now, you'll see that "Profile Content" and "Profile Footer" take up two lines just below the app bar. You want to change the `_ProfileContent` widget to take up all available vertical space in the viewport, except what's needed for the AppBar and fixed footer. Since the AppBar is higher up in the hierarchy, you don't need to worry about it here. But to negotiate space between the main content and the footer, you can use the [`Expanded`](https://api.flutter.dev/flutter/widgets/Expanded-class.html) widget.

You can use `Expanded` inside of [`Column`](https://api.flutter.dev/flutter/widgets/Column-class.html) and [`Row`](https://api.flutter.dev/flutter/widgets/Row-class.html) (as well as [`Flex`](https://api.flutter.dev/flutter/widgets/Flex-class.html), which is the generic version of both). It takes up as much free space as it can. If you use multiple `Expanded` widgets, the free space will be shared equally between them. It's very similar to `flex: 1` in a CSS flexbox layout.

:::warning
`Expanded` doesn't have to be an immediate child of a `Row` or `Column`—there can be other widgets in between, as long as they're all StatelessWidgets or StatefulWidgets. But be very careful about putting too much between them. If Flutter can't find the Row or Column intended as the parent, it will throw an error. In particular, **avoid putting the Row/Column in one widget and the Expanded in another**—that makes it way too easy to use the latter without the former, causing a runtime error.
:::

Update the RevExProfilePage build method as follows:

```dart
@override
Widget build(BuildContext context) {
  return RevExScaffold(
    title: "Profile",
    body: FutureBuilder(
      future: user,
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const CircularProgressIndicator();
        }

        if (snapshot.hasError) {
          return const Text('Error: Cannot get user data.');
        }

        final user = snapshot.data;

        return Column(
          children: [
            Expanded(      // <= Expanded added here
              child: _ProfileContent(),
            ),
            _ProfileFixedFooter(),
          ],
        );
      },
    ),
  );
}
```

:::tip
To quickly wrap a widget with another widget (something you'll be doing a lot), click the widget you want to wrap and open the context actions. Then select **Wrap with widget...** and swap out the `widget` text for whatever you need.

You'll notice several other **Wrap with** options. They name some of the most commonly used widgets in Flutter layouts. By the end of this course, you'll be familiar with all of them.

Depending on where you are in the layout, options like **Remove this widget**, which deletes the widget from the build method but leaves the rest of the hierarchy (parent and child widgets) intact, and **Move widget down**, which swaps the widget with its immediate child, are also available. Using these context actions is much easier than trying to alter deeply nested widget trees by hand.
:::

Now if you look at the app, "Profile Content" appears just below the app bar, and "Profile Footer" appears at the bottom of the screen.