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

Understanding side effects

In the Using Scaffold() to structure your screen section of Chapter 6, Putting Pieces Together, I showed you how to display a snack bar using rememberCoroutineScope {} and scaffoldState.snackbarHostState.showSnackbar(). As showSnackbar() is a suspending function, it must be called from a coroutine or another suspending function. Therefore, we created and remembered CoroutineScope using rememberCoroutineScope() and invoked its launch {} function.

Invoking suspending functions

The LaunchedEffect() composable is an alternative approach for spawning a suspending function. To see how it works, let's look at the LaunchedEffectDemo() composable. It belongs to the EffectDemo sample, as illustrated in the following screenshot:

Figure 7.1 – The EffectDemo sample showing LaunchedEffectDemo()

LaunchedEffectDemo() implements a counter. Once the Start button has been clicked, a counter is incremented every second. Clicking on...