Flutter Crash Course: A Journey from Basic Screens to Navigation

This blog post summarizes a Flutter crash course, covering topics from creating basic screens and layouts to handling images, custom fonts, dynamic data models, and navigation. It's designed to help developers learn Flutter efficiently by breaking down complex concepts into manageable lessons. The course is sponsored by freeCodeCamp.org.

Getting Started with Flutter

To follow along, you'll need a popular operating system, the latest version of Flutter installed, and an iOS simulator or Android emulator. If you need help setting up Flutter, you can find stepbystep videos on the Flutter Crash Course website.

Prerequisites

The course assumes you have experience with at least one programming language and have coded a website, web app, or mobile app previously. This ensures you possess basic programming skills.

Chapter 1: Creating a Basic Screen and Layout

This chapter focuses on layout in Flutter, using the Column widget to arrange widgets from top to bottom. The goal is to replicate a location detail screen where elements are stacked vertically.

Implementing Text Sections

You'll learn how to implement text sections to define areas for content, such as summaries and snippets of text. The initial home page is renamed to location detail, following a specific code organization convention.

Understanding the Column Widget

The Column widget lets you layout widgets from top to bottom. Row, on the other hand, lets you lay out stuff from left to right.

Using the Container Widget

The Container widget is introduced as a flexible bounding area, similar to a div in HTML. You can define parameters like color and decoration (using BoxDecoration) to style the container.

Main Axis Alignment and Cross Axis Alignment

The chapter explains main axis alignment, which controls how children are vertically spaced in a column. Options include spaceEvenly, end, and start. Cross axis alignment, on the other hand, controls horizontal alignment. A common option is stretch, which stretches items from left to right.

Creating a Reusable Text Section Widget

The code is cleaned up by creating a reusable TextSection widget. This widget is parameterized to customize its background color. The concept of private members (using an underscore prefix) and custom constructors is introduced.

Adding Images to Your Flutter App

This section covers adding images to your Flutter app using image assets and URLs. The focus is on importing an image asset (JPEG file) into your project and including it in the pubspec.yaml file.

Importing Image Assets

A new directory called assets/images is created to store image files. The pubspec.yaml file is modified to include the assets section, pointing to the assets/images directory.

Implementing the Image Banner Widget

A new widget called ImageBanner is created to display the image at the top of the screen. The widget takes the file name as a parameter. The Image widget is wrapped in a Container to provide styling options like padding and height.

Using Constraints and Box Fit

Constraints are used to specify the height of the image. BoxFit.cover is used to fill the image as much as possible within its container.

Working with Custom Fonts and Text Themes

This chapter demonstrates how to use custom fonts and text theming in Flutter. It builds upon the previous lessons by adding text sections to the detail screen and styling them with custom fonts.

Implementing the Text Section Widget (Continued)

The TextSection widget is enhanced to display a title and body. Padding is added to the text using the Container widget and EdgeInsets.

Adding Custom Fonts

Font files are added to the assets/fonts directory. The pubspec.yaml file is updated to include the fonts section, specifying the font family and file paths.

Using Text Themes

Text theming is introduced as a way to define styles in one place and apply them consistently throughout the app. The MaterialApp widget is used to define a theme, including the app bar theme and text theme.

Defining Styles in a Separate File

A separate file called style.dart is created to define all the styles for the app. Constants are used to keep the style file organized and clear. The title and body text styles are defined in the style.dart file and applied to the TextSection widget.

Dynamic Data with Models, Generics and More

This section dives into using models to represent data and functionality and updating the code to make screens dynamic. It also covers Dart concepts like generics, the map function, anonymous functions, and cascades.

Creating Data Models

Two classes are created, Location and LocationFact, to represent the data for the tourism app. A onetomany relationship is established between Location and LocationFact.

Adding Business Logic to the Model

A static method called fetchAll is added to the Location class to fetch a list of locations. The method returns a hardcoded list of locations for now, but will later be replaced with a web service API call.

Making the Code Dynamic

The LocationDetailScreen is updated to use the fetchAll function and display the data dynamically. The map function is used to convert a list of LocationFact objects to a list of TextSection widgets.

Using the Cascade Operator

The cascade operator (..) is used to add all the TextSection widgets to the children list of the Column widget.

Navigation and List Views

This chapter focuses on navigation in Flutter and introduces the ListView widget, which is used to display scrollable lists of data. It also covers the GestureDetector widget for handling user interactions.

Updating Fixture Data

The fixture data is updated to include more locations and a new field called id is added to the Location model.

Implementing the Location Listing Screen

A new screen called LocationsScreen is created to display a list of locations. The ListView widget is used to render the list of locations. The code initializes a `ListView` with placeholder entries. Actual screen styling is a topic for future tutorials.

Using Gesture Detectors

The GestureDetector widget is used to detect taps on list view items. The onTap parameter is used to navigate to the LocationDetailScreen when an item is tapped.

Understanding Navigation Concepts

Navigation in Flutter is explained as a deck of cards, where each card represents a screen. When you navigate to a new screen, you're pushing a new card on top of the deck. When you go back, you're popping a card off the top of the deck. You're defining these screens with routes.

Implementing Navigation (Correctly)

The course demonstrates how to use named routes and the Navigator class to navigate between screens. A shortcoming of standard Flutter is that routes can't pass dynamic arguments, so the course demonstrates using Navigator.pushNamed with argument Maps to push arguments to the destination screen.

Using the `onGenerateRoute` Parameter

The onGenerateRoute parameter of the MaterialApp widget is used to generate routes dynamically based on the route name and arguments. This is a best practice.

This summary outlines the key concepts and steps involved in building a Flutter app from scratch, providing a solid foundation for further exploration and development.