Book Image

Mastering Android Development with Kotlin

By : Miloš Vasić
Book Image

Mastering Android Development with Kotlin

By: Miloš Vasić

Overview of this book

Kotlin is a programming language intended to be a better Java, and it's designed to be usable and readable across large teams with different levels of knowledge. As a language, it helps developers build amazing Android applications in an easy and effective way. This book begins by giving you a strong grasp of Kotlin's features in the context of Android development and its APIs. Moving on, you'll take steps towards building stunning applications for Android. The book will show you how to set up the environment, and the difficulty level will grow steadily with the applications covered in the upcoming chapters. Later on, the book will introduce you to the Android Studio IDE, which plays an integral role in Android development. We'll use Kotlin's basic programming concepts such as functions, lambdas, properties, object-oriented code, safety aspects, type parameterization, testing, and concurrency, which will guide you through writing Kotlin code in production. We'll also show you how to integrate Kotlin into any existing Android project.
Table of Contents (24 chapters)
Title Page
Credits
About the Author
Acknowledgments
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Understanding fragments


We have mentioned that the central part of our main screen will contain a list of filtered items. We want to have several pages with a different set of filters applied. A user will be able to swipe left or right to change the filtered content and navigate through the following pages:

  • All displayed
  • Items for Today
  • Items for Next 7 Days
  • Only Notes
  • Only TODOs

To achieve this functionality, we will need to define fragments. What are fragments and what is their purpose?

A fragment is a portion of the interface of an Activity instance. You can use fragments to create multiplane screens or screens with view paging, like in our case.

Just like activities, fragments have their own lifecycle. Fragment lifecycle is presented in the following diagram:

There are some additional methods that activities do not have:

  • onAttach(): This is executed when a fragment is associated to an activity.
  • onCreateView(): This instantiates and returns a fragment's view instance.
  • onActivityCreated(): This executes...