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

14.4 Saving the State

The first step in extending the StateChange application is to make sure that the text entered by the user is extracted from the EditText component within the onSaveInstanceState() method of the MainActivity activity, and then saved as a key-value pair into the Bundle object.

In order to extract the text from the EditText object we first need to identify that object in the user interface. Clearly, this involves bridging the gap between the Java code for the activity (contained in the MainActivity.java source code file) and the XML representation of the user interface (contained within the content_main.xml resource file). In order to extract the text entered into the EditText component we need to gain access to that user interface object.

Each component within a user interface has associated with it a unique identifier. By default, the Layout Editor tool constructs the ID for a newly added component from the object type. If more than one view of the same...