Book Image

Android UI Development with Jetpack Compose

By : Thomas Künneth
Book Image

Android UI Development with Jetpack Compose

By: Thomas Künneth

Overview of this book

Jetpack Compose is Android’s new framework for building fast, beautiful, and reliable native user interfaces. It simplifies and significantly accelerates UI development on Android using the declarative approach. This book will help developers to get hands-on with Jetpack Compose and adopt a modern way of building Android applications. The book is not an introduction to Android development, but it will build on your knowledge of how Android apps are developed. Complete with hands-on examples, this easy-to-follow guide will get you up to speed with the fundamentals of Jetpack Compose such as state hoisting, unidirectional data flow, and composition over inheritance and help you build your own Android apps using Compose. You'll also cover concepts such as testing, animation, and interoperability with the existing Android UI toolkit. By the end of the book, you'll be able to write your own Android apps using Jetpack Compose.
Table of Contents (16 chapters)
Part 1:Fundamentals of Jetpack Compose
Part 2:Building User Interfaces
Part 3:Advanced Topics

Looking closer at composable functions

The UI of a Compose app is built by writing and calling composable functions. We have already done both in the previous chapters, but my explanations regarding the structure of a composable, as well as its internals, have been quite basic – it's time to fix that.

Building blocks of composable functions

A composable function is a Kotlin function that has been annotated with @Composable.
All composables must be marked this way because the annotation informs the Compose compiler that the function converts data into UI elements.

The signature of a Kotlin function consists of the following parts or building blocks:

  • An optional visibility modifier (private, protected, internal, or public)
  • The fun keyword
  • A name
  • A list of parameters (can be empty) or, optionally, a default value
  • An optional return type
  • A block of code

Let's explore these parts in greater detail.

The default visibility...