Book Image

Android Studio 3.5 Development Essentials - Kotlin Edition

By : Neil Smyth
Book Image

Android Studio 3.5 Development Essentials - Kotlin Edition

By: Neil Smyth

Overview of this book

Popularity of Kotlin as an Android-compatible language keeps growing every day. This book will help you to build your own Android applications using Kotlin. Android Studio 3.5 Development Essentials Kotlin 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 emulators. You will test apps on physical android devices, then study Android Studio code editor, Android architecture, and the anatomy of an Android app. The focus then shifts to Kotlin language. You’ll get an overview of Kotlin language and practice converting code from Java to Kotlin. You’ll also explore Kotlin data types, operators, expressions, loops, functions, and the basics of OOP concept in Kotlin. This book will then cover Android Jetpack and how to create an example app project using ViewModel component, as well as advanced topics such as views and widgets implementation, multi-window support integration, and biometric authentication. Finally, you will learn to upload your app to the 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 Kotlin.
Table of Contents (93 chapters)
93
Index

33.1 Intercepting Touch Events

Touch events can be intercepted by a view object through the registration of an onTouchListener event listener and the implementation of the corresponding onTouch() callback method or lambda. The following code, for example, ensures that any touches on a ConstraintLayout view instance named myLayout result in a call to a lambda expression:

myLayout.setOnTouchListener {v: View, m: MotionEvent ->

            // Perform tasks here

            true

}

Of course, the above code could also be implemented by using a function instead of a lambda as follows, though the lambda approach results in more compact and readable code:

myLayout.setOnTouchListener(object : View.OnTouchListener {

    override fun onTouch(v: View, m: MotionEvent): Boolean {

        // Perform...