Book Image

Android Studio 4.0 Development Essentials - Java Edition

By : Neil Smyth
Book Image

Android Studio 4.0 Development Essentials - Java Edition

By: Neil Smyth

Overview of this book

Android rolls out frequent updates to meet the demands of the dynamic mobile market and to enable its developer community to lead advancements in application development. This book focuses on the updated features of Android Studio (the fully integrated development environment launched by Google) to build reliable Android applications using Java. The book starts by outlining the steps necessary to set up an Android development and testing environment. You’ll then learn how to create user interfaces with the help of Android Studio Layout Editor, XML files, and by writing the code in Java. The book introduces you to Android architecture components and advanced topics such as intents, touchscreen handling, gesture recognition, multi-window support integration, and biometric authentication, and lets you explore key features of Android Studio 4.0, including the layout editor, direct reply notifications, and dynamic delivery. You’ll also cover Android Jetpack in detail and create a sample app project using the ViewModel component. Finally, you’ll upload your app to the Google Play Console and handle the build process with Gradle. By the end of this book, you’ll have gained the skills necessary to develop applications using Android Studio 4.0 and Java.
Table of Contents (88 chapters)
88
Index

37.3 Saving and Restoring State

An object or value can be saved from within the ViewModel by passing it through to the set() method of the SavedStateHandle instance, providing the key string by which it is to be referenced when performing a retrieval:

private static final String NAME_KEY = "Customer Name";

 

savedStateHandle.set(NAME_KEY, customerName;

When used with LiveData objects, a previously saved value may be restored using the getLiveData() method of the SavedStateHandle instance, once again referencing the corresponding key as follows:

MutableLiveData<String> restoredName = savedStateHandle.getLiveData(NAME_KEY);

To restore a normal (non-LiveData) object, simply use the SavedStateHandle get() method:

String restoredName = savedStateHandle.get(NAME_KEY);

Other useful SavedStateHandle methods include the following:

contains(String key) - Returns a boolean value indicating whether the saved state contains a value for the...