Book Image

Android Studio 4.0 Development Essentials - Kotlin Edition

By : Neil Smyth
Book Image

Android Studio 4.0 Development Essentials - Kotlin Edition

By: Neil Smyth

Overview of this book

Kotlin as an Android-compatible programming language is becoming increasingly popular. Fully updated for Android Studio 4.0, this book will teach you the skills necessary to develop Android-based applications using Kotlin. Starting with the basics, this book outlines the steps necessary to set up Android development and testing environments, and goes on to introduce you to programming in Kotlin. You’ll practice Java to Kotlin code conversion and explore data types, operators, expressions, loops, functions, as well as the basics of OOP in Kotlin. You’ll then learn about Android architecture components and advanced topics, such as intents, touchscreen handling, gesture recognition, multi-window support integration, and biometric authentication. As you make progress, you’ll explore Android Studio 4.0’s key features, including layout editor, direct reply notifications, and dynamic delivery. You’ll also delve into Android Jetpack and create a sample app project using ViewModel, the Android Jetpack component. Finally, you will upload your app to Google Play Console and model the build process using Gradle. By the end of this Android book, you’ll be fully prepared to develop applications using Android Studio 4.0 and Kotlin.
Table of Contents (97 chapters)
97
Index

44. An Android ViewModel Saved State Tutorial

The preservation and restoration of app state is all about presenting the user with continuity in terms of appearance and behavior after an app is placed into the background. Users have come to expect to be able to switch from one app to another and, on returning to the original app, to find it in the exact state it was in before the switch took place.

As outlined in the chapter entitled “Understanding Android Application and Activity Lifecycles”, when the user places an app into the background that app becomes eligible for termination by the operating system in the event that resources become constrained. When the user attempts to return the terminated app to the foreground, Android simply relaunches the app in a new process. Since this is all invisible to the user, it is the responsibility of the app to restore itself to the same state it was in when the app was originally placed in the background instead of presenting...