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 stateful and stateless composable functions

In this section, I will show you the difference between stateful and stateless composable functions. To understand why this is important, let’s first focus on the term state.

In the previous chapters, I described state as data that can change over time. Where the data is held (e.g., a SQLite database, a file, or a value inside an object) does not matter. What is important is that the UI must always show the current data. Therefore, if a value changes, the UI must be notified. To achieve this, we use observable types. This is not specific to Jetpack Compose and is a common pattern in many frameworks, programming languages, and platforms. For example, Kotlin supports observables through property delegates. Let’s see how they work.

Please note that the following code snippet is not an Android app. While you could execute it in Android Studio using a Scratch File, there’s a much easier way – Kotlin...