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

11.1 Find View by ID

As outlined in the chapter entitled “The Anatomy of an Android Application”, all of the resources that make up an application are compiled into a class named R. Amongst those resources are those that define layouts. Within the R class is a subclass named layout, which contains the layout resources, including the views that make up the user interface. Most apps will need to implement interaction between the code and these views, for example when reading the value entered into the EditText view or changing the content displayed on a TextView.

Prior to the introduction of Android Studio 3.6, the only option for gaining access to a view from within the app code involved writing code to manually find a view based on its id via a method named findViewById(). For example:

TextView exampleView = findViewById(R.id.exampleView);

With the reference obtained, the properties of the view can then be accessed. For example:

exampleView.setText("Hello...