Book Image

Android Studio 4.0 Development Essentials - Kotlin Edition

By : Neil Smyth
Book Image

Android Studio 4.0 Development Essentials - Kotlin Edition

By: Neil Smyth

Overview of this book

Kotlin as an Android-compatible programming language is becoming increasingly popular. Fully updated for Android Studio 4.0, this book will teach you the skills necessary to develop Android-based applications using Kotlin. Starting with the basics, this book outlines the steps necessary to set up Android development and testing environments, and goes on to introduce you to programming in Kotlin. You’ll practice Java to Kotlin code conversion and explore data types, operators, expressions, loops, functions, as well as the basics of OOP in Kotlin. You’ll then learn about Android architecture components and advanced topics, such as intents, touchscreen handling, gesture recognition, multi-window support integration, and biometric authentication. As you make progress, you’ll explore Android Studio 4.0’s key features, including layout editor, direct reply notifications, and dynamic delivery. You’ll also delve into Android Jetpack and create a sample app project using ViewModel, the Android Jetpack component. Finally, you will upload your app to Google Play Console and model the build process using Gradle. By the end of this Android book, you’ll be fully prepared to develop applications using Android Studio 4.0 and Kotlin.
Table of Contents (97 chapters)
97
Index

78.5 Reading the Content of a File

The exact steps required to read the content of a file hosted by a document provider will depend to a large extent on the type of the file. The steps to read lines from a text file, for example, differ from those for image or audio files.

An image file can be assigned to a Bitmap object by extracting the file descriptor from the Uri object and then decoding the image into a BitmapFactory instance. For example:

val pFileDescriptor = contentResolver.openFileDescriptor(uri, "r")

val fileDescriptor = pFileDescriptor.fileDescriptor

 

val image = BitmapFactory.decodeFileDescriptor(fileDescriptor)

 

pFileDescriptor.close()

 

val myImageView = ImageView(this)

myImageView.setImageBitmap(image)

Note that the file descriptor is opened in “r” mode. This indicates that the file is to be opened for reading. Other options are “w” for write access and “rwt” for read...