Book Image

Android UI Development with Jetpack Compose - Second Edition

By : Thomas Künneth
5 (1)
Book Image

Android UI Development with Jetpack Compose - Second Edition

5 (1)
By: Thomas Künneth

Overview of this book

Compose has caused a paradigm shift in Android development, introducing a variety of new concepts that are essential to an Android developer’s learning journey. It solves a lot of pain points associated with Android development and is touted to become the default way to building Android apps over the next few years. This second edition has been thoroughly updated to reflect all changes and additions that were made by Google since the initial stable release, and all examples are based on Material 3 (also called Material You). This book uses practical examples to help you understand the fundamental concepts of Jetpack Compose and how to use them when you are building your own Android applications. You’ll begin by getting an in-depth explanation of the declarative approach, along with its differences from and advantages over traditional user interface (UI) frameworks. Having laid this foundation, the next set of chapters take a practical approach to show you how to write your first composable function. The chapters will also help you master layouts, an important core component of every UI framework, and then move to more advanced topics such as animation, testing, and architectural best practices. By the end of this book, you’ll be able to write your own Android apps using Jetpack Compose and Material Design.
Table of Contents (18 chapters)
Part 1: Fundamentals of Jetpack Compose
Part 2: Building User Interfaces
Part 3: Advanced Topics

Understanding semantics

Unlike the traditional view system, Jetpack Compose does not use references to identify individual UI elements. Please remember that such references are needed in an imperative approach to modify the component tree during runtime. But this is not how Compose works—instead, we declare how the UI should look based on state. Yet, to test if a particular composable looks and behaves as expected, we need to find it among all other children of a Compose hierarchy.

This is where the semantics tree comes into play. As the name implies, semantics give meaning to a UI element or element hierarchies. The semantics tree is generated alongside the UI hierarchy, which it describes using attributes such as Role, Text, and Actions. It is used for accessibility and testing.

In the previous section, I showed you a simple test case that checks if a button text matches a given string. Here is another test case. testLetterAfterButtonClickIsB() performs a click on the...