Book Image

Android Studio 4.1 Development Essentials – Kotlin Edition

By : Neil Smyth
Book Image

Android Studio 4.1 Development Essentials – Kotlin Edition

By: Neil Smyth

Overview of this book

Android 11 has a ton of new capabilities. It comes up with three foci: a people-centric approach to communication, controls to let users quickly access and manage all of their smart devices, and privacy to give users more ways to control how data on devices is shared. This book starts off with the steps necessary to set up an Android development and testing environment, followed by an introduction to programming in Kotlin. An overview of Android Studio and its architecture is provided, followed by an in-depth look at the design of Android applications and user interfaces using the Android Studio environment. You will also learn about the Android architecture components along with some advanced topics such as touch screen handling, gesture recognition, the recording and playback of audio, app links, dynamic delivery, the AndroidStudio profiler, Gradle build configuration, and submitting apps to the Google Play Developer Console. The concepts of material design are also covered in detail. This edition of the book also covers printing, transitions, and cloud-based file storage; foldable device support is the cherry on the cake. By the end of this course, you will be able to develop Android 11 Apps using Android Studio 4.1, Kotlin, and Android Jetpack. The code files for the book can be found here: https://www.ebookfrenzy.com/retail/as41kotlin/index.php
Table of Contents (95 chapters)
95
Index

39.4 The ViewModel Component

The purpose of ViewModel is to separate the user interface-related data model and logic of an app from the code responsible for actually displaying and managing the user interface and interacting with the operating system. When designed in this way, an app will consist of one or more UI Controllers, such as an activity, together with ViewModel instances responsible for handling the data needed by those controllers.

In effect, the ViewModel only knows about the data model and corresponding logic. It knows nothing about the user interface and makes no attempt to directly access or respond to events relating to views within the user interface. When a UI controller needs data to display, it simply asks the ViewModel to provide it. Similarly, when the user enters data into a view within the user interface, the UI controller passes it to the ViewModel for handling.

This separation of responsibility addresses the issues relating to the lifecycle of UI controllers...