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

Hoisting state and passing events

So, state is any value that can change over time. As Jetpack Compose is a declarative UI framework, the only way to update a composable is to call it with new arguments. This happens automatically when state that a composable is using changes. State hoisting is a pattern of moving state up to make a composable function stateless.

Besides making a composable more easily reusable and testable, moving state up is necessary to use it in more than one composable function. You have already seen this in quite a few of my sample apps. For example, in the Composing and recomposing the user interface section of Chapter 3, Exploring the Key Principles of Compose, we used three sliders to create and display a color.

While state controls the visual representation of a composable function (that is, how it looks on screen), events notify a part of a program that something has happened. Let’s focus a little more on this. My sample FlowOfEventsDemo app...