MDC-101 Flutter: Material Components (MDC) Basics (Flutter)

What are Material Design and Material Components for Flutter?

Material Design is a system for building bold and beautiful digital products. By uniting style, branding, interaction, and motion under a consistent set of principles and components, product teams can realize their greatest design potential.

Material Components for Flutter (MDC-Flutter) unite design and engineering with a library of components that create a consistent user experience across apps and platforms. As the Material Design system evolves, these components are updated to ensure consistent pixel-perfect implementation, adhering to Google's front-end development standards. MDC is also available for Android, iOS, and the web.

In this codelab, you'll build a login page using several of MDC Flutter's components.

What you'll build

This codelab is the first of four codelabs that will guide you through building an app called Shrine, an e-commerce app that sells clothing and home goods. It will demonstrate how you can customize components to reflect any brand or style using MDC-Flutter.

In this codelab, you'll build a login page for Shrine that contains:

• An image of Shrine's logo
• The name of the app (Shrine)
• Two text fields, one for entering a username and the other for a password
• Two buttons

The related codelabs can be found at: MDC-102: Material Design Structure and Layout MDC-103: Material Design Theming with Color, Shape, Elevation and Type MDC-104: Material Design Advanced Components

By the end of MDC-104, you'll build an app that looks like this:

MDC components in this codelab

• Text field
• Button
• Ripple

In this codelab you'll use the default components provided by MDC-Flutter. You'll learn to customize them in MDC-103: Material Design Theming with Color, Shape, Elevation and Type.

How would you rate your level of experience with Flutter development?

Novice Intermediate Proficient

Prerequisites

To start developing mobile apps with Flutter you need:

• the Flutter SDK
• an IntelliJ IDE with Flutter plugins, or your favorite code editor

Flutter's IDE tools are available for Android Studio, IntelliJ IDEA Community (free), and IntelliJ IDEA Ultimate.

To build and run Flutter apps on iOS:

• a computer running macOS
• Xcode 9 or newer
• iOS Simulator, or a physical iOS device

To build and run Flutter apps on Android:

• a computer running macOS, Windows, or Linux
• Android Studio
• Android Emulator (comes with Android Studio), or a physical Android device

Get detailed Flutter setup information

Important: If an Allow USB debugging dialog appears on the Android phone connected to the codelab machine, enable the Always allow from this computer option and click OK.

Before proceeding with this codelab, make sure that your SDK is in the right state. If the flutter SDK was installed previously, then use flutter upgrade to ensure that the SDK is at the latest state.

 flutter upgrade

Running flutter upgrade will automatically run flutter doctor. If this a fresh flutter install and no upgrade was necessary, then run flutter doctor manually. See that all the check marks are showing; this will download any missing SDK files you need and ensure that your codelab machine is set up correctly for Flutter development.

 flutter doctor

Download starter project

The starter project is located in the material-components-flutter-codelabs-101-starter/mdc_100_series directory.

...or clone it from GitHub

To clone this codelab from GitHub, run the following commands:

git clone https://github.com/material-components/material-components-flutter-codelabs.git
cd material-components-flutter-codelabs
git checkout 101-starter

For more help: Cloning a repository from GitHub

The right branch

Codelabs MDC-101 through 104 consecutively build upon each other. So when you finish the code for 101, it becomes the starter code for 102! The code is divided across different branches, and you can list them all with this command:

git branch --list

To see the completed code, checkout the 102-starter_and_101-complete branch.

Set up your project

The following instructions assume you're using Android Studio (IntelliJ).

Open the project

1. Open Android Studio.
2. If you see the welcome screen, click Open an existing Android Studio project.
3. Navigate to the material-components-flutter-codelabs/mdc_100_series directory and click Open. The project should open. You can ignore any errors you see in analysis until you've built the project once.
4. In the project panel on the left, if you see the testing file ../test/widget_test.dart delete it.
5. If prompted, install any platform and plugin updates or FlutterRunConfigurationType, then restart Android Studio.

Tip: Make sure you have the plugins installed for Flutter and Dart.

Run the starter app

The following instructions assume you're testing on an Android emulator or device but you can also test on an iOS Simulator or device if you have Xcode installed.

1. Select the device or emulator. If the Android emulator is not already running, select Tools -> Android -> AVD Manager to create a virtual device and start the emulator. If an AVD already exists, you can start the emulator directly from the device selector in IntelliJ, as shown in the next step. (For the iOS Simulator, if it is not already running, launch the simulator on your development machine by selecting Flutter Device Selection -> Open iOS Simulator.)

2. Start your Flutter app: Look for the Flutter Device Selection dropdown menu at the top of your editor screen, and select the device (for example, iPhone SE or Android SDK built for <version>). Press the Play icon ().

If you were unable to run the app successfully, stop and troubleshoot your developer environment. Try navigating to material-components-flutter-codelabs or if you downloaded the .zip file material-components-flutter-codelabs-...) in the terminal and running flutter create mdc_100_series.

Success! The starter code for Shrine's login page should be running in your simulator. You should see the Shrine logo and the name "Shrine" just below it.

If you see any warnings about the pubspec having been edited (with prompts to get dependencies), just leave them alone. When you press the play button, it runs flutter packages get for you!

flutter packages get installs dependencies you have listed in your pubspec.yaml file. You can write your own packages to be published on Pub. This codelab series uses a custom package shrine_images for the product images you'll see in MDC-102.

flutter packages get invokes the underlying Dart pub package manager to install all the dependencies for your Flutter app. In this codelab series we use a custom package shrine_images for the product images.

For more information on packages, see Using Packages.

Let's look at the code.

Widgets in login.dart

Open up login.dart. It should contain this:

import 'package:flutter/material.dart';

class LoginPage extends StatefulWidget {
  @override
  _LoginPageState createState() => _LoginPageState();
}

class _LoginPageState extends State<LoginPage> {
  // TODO: Add text editing controllers (101)
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: ListView(
          padding: EdgeInsets.symmetric(horizontal: 24.0),
          children: <Widget>[
            SizedBox(height: 80.0),
            Column(
              children: <Widget>[
                Image.asset('assets/diamond.png'),
                SizedBox(height: 16.0),
                Text('SHRINE'),
              ],
            ),
            SizedBox(height: 120.0),
            // TODO: Wrap Username with AccentColorOverride (103)
            // TODO: Remove filled: true values (103)
            // TODO: Wrap Password with AccentColorOverride (103)
            // TODO: Add TextField widgets (101)
            // TODO: Add button bar (101)
          ],
        ),
      ),
    );
  }
}

// TODO: Add AccentColorOverride (103)

Notice that it contains an import statement and two new classes:

• The import statement brings Material Components into this file.
• The LoginPage class represents the entire page displayed in the simulator.
• The _LoginPageState class's build() function controls how all the widgets in our UI are created.

For more of the basics of the Flutter UI and what widgets are, you can take a Tour of the Flutter Widget Framework or do the codelab Write Your First Flutter App, part 1.

To begin, we'll add two text fields to our login page, where users enter their username and password. We'll use the TextField widget, which displays a floating label and activates a touch ripple.

Material's text fields have been greatly enhanced to improve brand flexibility, with improvements backed by extensive user experience (UX) research for better usability and visual design.

Learn more about the new text fields in their article of the Material Guidelines.

This page is structured primarily with a ListView, which arranges its children in a scrollable column. Let's place text fields at the bottom.

Add the TextField widgets

Add two new text fields and a spacer after SizedBox(height: 120.0).

// TODO: Add TextField widgets (101)
// [Name]
TextField(
  decoration: InputDecoration(
    filled: true,
    labelText: 'Username',
  ),
),
// spacer
SizedBox(height: 12.0),
// [Password]
TextField(
  decoration: InputDecoration(
    filled: true,
    labelText: 'Password',
  ),
  obscureText: true,
),

The text fields each have a decoration: field that takes an InputDecoration widget. The filled: field means the background of the text field is lightly filled in to help people recognize the tap or touch target area of the text field. The second text field's obscureText: true value automatically replaces the input that the user types with bullets, which is appropriate for passwords.

Save your project (with the keystroke: command + s) which performs a hot reload.

You should now see a page with two text fields for Username and Password! Check out the floating label and ink ripple animations:

If the app doesn't update, click the "Play" button again, or click "Stop" followed by "Play."

TextField features include:

• The TextField widget's look can be easily changed. For the decoration field, specify an InputDecoration value.
• The MDC text field displays touch feedback (called the MDC ripple or "ink") by default.
• The FormField is a similar widget that has special features for embedding fields in Forms.
• TextField class documentation

Next, we'll add two buttons to our login page: "Cancel" and "Next." We'll use two kinds of MDC button widgets: the FlatButton (called the "Text Button" in the Material Guidelines) and the RaisedButton (referred to as the "Contained Button").

Choosing between text and contained buttons

Why not simply display two contained buttons? Each button type indicates which actions are more important than others.

A layout should contain a single prominent button. This makes it clear that other buttons have less importance. This prominent button represents the action we most want our users to take in order to advance through our app.

The action we'd least like them to take is cancelling the login. Because a contained button draws the eye with its raised appearance, it should be used for the more important action. By comparison, the plain text button to the left of it looks less emphasized.

Learn more about button hierarchy in the Buttons article of the Material Guidelines.

Add the ButtonBar

After the text fields, add the ButtonBar to the ListView's children:

// TODO: Add button bar (101)
ButtonBar(
  // TODO: Add a beveled rectangular border to CANCEL (103)
  children: <Widget>[
    // TODO: Add buttons (101)
  ],
),

The ButtonBar arranges its children in a row.

Add the buttons

Then add two buttons to the ButtonBar's list of children:

    // TODO: Add buttons (101)
    FlatButton(
      child: Text('CANCEL'),
      onPressed: () {
        // TODO: Clear the text fields (101)
      },
    ),
    // TODO: Add an elevation to NEXT (103)
    // TODO: Add a beveled rectangular border to NEXT (103)
    RaisedButton(
      child: Text('NEXT'),
      onPressed: () {
    // TODO: Show the next page (101) 
      },
    ),

Why do we have empty blocks for the onPressed: fields?

If we passed null, or didn't include the field (which then defaults to null), the buttons would become disabled. There would be no feedback on touch and we couldn't get a good idea of their enabled behavior. Using empty blocks prevents them from being disabled.

For more information on buttons and their interactions, see Adding Interactivity to Your App.

Save your project. Under the last text field, you should see two buttons appear:

The ButtonBar handles the layout work for you. It positions the buttons horizontally, so they appear next to one another, according to the padding in the current ButtonTheme. (You'll learn more about that in codelab MDC-103.)

Touching a button initiates an ink ripple animation, without causing anything else to happen. Let's add functionality into the anonymous onPressed: functions, so that the cancel button clears the text fields, and the next button dismisses the screen:

Add TextEditingControllers

To make it possible to clear the text fields' values, we'll add TextEditingControllers to control their text.

Right under the _LoginPageState class's declaration, add the controllers as final variables.

  // TODO: Add text editing controllers (101)
  final _usernameController = TextEditingController();
  final _passwordController = TextEditingController();

On the first text field's controller: field, set the _usernameController:

// [Name]
TextField(
  controller: _usernameController,

On the second text field's controller: field, now set the _passwordController:

// [Password]
TextField(
  controller: _passwordController,

Edit onPressed

Add a command to clear each controller in the FlatButton's onPressed: function:

    // TODO: Clear the text fields (101)
    _usernameController.clear();
    _passwordController.clear();

Save your project. Now when you type something into the text fields, hitting cancel clears each field again.

This login form is in good shape! Let's advance our users to the rest of the Shrine app.

Pop

To dismiss this view, we want to pop (or remove) this page (which Flutter calls a route) off the navigation stack.

Navigator maintains a stack of routes just like UINavigationController on iOS. Pushing a route places it at the top of the stack. Popping the stack removes the most recently added route. In app.dart of our app, calling initialRoute: '/login', adds the login screen to the Navigator, on top of what is passed in home:.

Learn more about routes and navigation in Navigation Basics.

In the RaisedButton's onPressed: function, pop the most recent route from the Navigator:

    // TODO: Show the next page (101) 
    RaisedButton(
      child: Text('NEXT'),
      onPressed: () {
        Navigator.pop(context);
      },
    ),

Lastly, open up home.dart and set resizeToAvoidBottomInset to false in the Scaffold:

    return Scaffold(
      // TODO: Add app bar (102)
      // TODO: Add a grid view (102)
      body: Center(
        child: Text('You did it!'),
      ),
      // TODO: Set resizeToAvoidBottomInset (101)
      resizeToAvoidBottomInset: false,
    );

Doing this ensures that they keyboard's appearance does not alter the size of the home page or its widgets.

That's it! Save the project. Go ahead and click "Next."

You did it!

This screen is the starting point for our next codelab, which you'll work on in MDC-102.

About Buttons:

• In addition to FlatButton and RaisedButton, there's OutlineButton, FloatingActionButton IconButton, and more.
• Browse buttons and their documentation in the MDC Widgets catalog.

We added text fields and buttons and hardly had to consider layout code. Material Components for Flutter come with a lot of style and can be laid out almost effortlessly.

The completed MDC-101 app is available in the 102-starter_and_101-complete branch.

You can test your version of the app against the app in that branch.

Next steps

Text fields and buttons are two core components in the Material System, but there are many more! You can also explore the rest of the widgets in Flutter's Material Components library.

Alternatively, head over to MDC-102: Material Design Structure and Layout to learn about the components covered in MDC-102 for Flutter.

I was able to complete this codelab with a reasonable amount of time and effort

Strongly agree Agree Neutral Disagree Strongly disagree

I would like to continue using Material Components in the future

Strongly agree Agree Neutral Disagree Strongly disagree