Book Image

Android Studio 3.5 Development Essentials - Java Edition

By : Neil Smyth
Book Image

Android Studio 3.5 Development Essentials - Java Edition

By: Neil Smyth

Overview of this book

Android applications have become an important part of our daily lives and lots of effort goes into developing an Android application. This book will help you to build you own Android applications using Java. Android Studio 3.5 Development Essentials – Java Edition first teaches you to install Android development and test environment on different operating systems. Next, you will create an Android app and a virtual device in Android Studio, and install an Android application on emulator. You will test apps on physical Android devices, then study Android Studio code editor and constraint layout, Android architecture, the anatomy of an Android app, and Android activity state changes. The book then covers advanced topics such as views and widgets implementation, multi-window support integration, and biometric authentication, and finally, you will learn to upload your app to Google Play console and handle the build process with Gradle. By the end of this book, you will have gained enough knowledge to develop powerful Android applications using Java.
Table of Contents (86 chapters)
86
Index

66.7 Modifying the ViewModel

The ViewModel is responsible for creating an instance of the repository and for providing methods and LiveData objects that can be utilized by the UI controller to keep the user interface synchronized with the underlying database. As implemented in ProductRepository.java, the repository constructor requires access to the application context in order to be able to get a Room Database instance. To make the application context accessible within the ViewModel so that it can be passed to the repository, the ViewModel needs to subclass AndroidViewModel instead of ViewModel. Begin, therefore, by editing the MainViewModel.java file (located in the Project tool window under app -> java -> com.ebookfrenzy.roomdemo -> ui.main) and changing the class to extend AndroidViewModel and to implement the default constructor:

package com.ebookfrenzy.roomdemo.ui.main;

 

import android.app.Application;

import androidx.lifecycle.AndroidViewModel;

...