Book Image

Learning Kotlin by building Android Applications

By : Eunice Adutwumwaa Obugyei, Natarajan Raman
Book Image

Learning Kotlin by building Android Applications

By: Eunice Adutwumwaa Obugyei, Natarajan Raman

Overview of this book

<p>Today Kotlin is an official programming language for Android development and is widely adopted. Kotlin is expressive, concise, and powerful. It also ensures seamless interoperability with existing Android languages like JAVA and C++, which means that it's even easier for developers to use.</p> <p>This book adopts a project-style approach, where we focus on teaching Android development by building three different Android Application: a Tic-Tac-Toe application, a location- based alarm and a To-Do list application.</p> <p>The book begins by giving you a strong grasp of the Kotlin language and its APIs as a preliminary to building stunning applications for Android. You'll learn to set up an environment and as you progress through the chapters and the building of the different applications, the difficulty level will steadily grow.</p> <p>The book also introduces you to the Android Studio IDE, which plays an integral role in Android Development. It covers Kotlin's basic programming concepts such as functions, lambdas, properties, object-oriented code, safety aspects and type parameterization, testing, and concurrency, and helps you write Kotlin code to production.</p> <p>Finally, you'll be taken through the process of releasing your app on the Google Play Store. You will also be introduced to other app distribution channels such as Amazon App Store.</p> <p>As a bonus chapter, you will also learn how to use the Google Faces API to detect faces and add fun functionalities.</p>

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Learning Kotlin by building Android Applications
Eunice Adutwumwaa Obugyei | Natarajan Raman
Jun, 2018 | 316 pages
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Table of Contents (21 chapters)
Title Page
Title Page
Packt Upsell
Packt Upsell
Contributors
Contributors
Preface
Preface
Free Chapter
1
Setting Up for Android Development
Setting Up for Android Development
Why develop Android with Kotlin?
Setting up your environment
Summary
2
Configuring Your Environment for Kotlin
Configuring Your Environment for Kotlin
Installing the Kotlin plugin
Making our project Kotlin-ready
Summary
3
Data Types, Variables, and Constants
Data Types, Variables, and Constants
The user interface
Basic types
Summary
4
Classes and Objects
Classes and Objects
Structure of a class
Objects
Summary
5
Type Checks and Null Safety
Type Checks and Null Safety
Null safety
Type checks
Summary
6
Functions and Lambdas
Functions and Lambdas
Functions
Higher–order functions and lambdas
Implementing a game status check
Summary
7
Developing Your Location-Based Alarm
Developing Your Location-Based Alarm
Creating a project
Generation of a Google Maps API key
Understanding the code
Customizing the code
Developing a screen for user input
The AndroidManifest file
Summary
8
Working with Google's Location Services
Working with Google's Location Services
Integrating shared preferences
Adding permissions
Integration of the location API
The Google API client
Matching the location
Summary
9
Connecting the Outside World – Networking
Connecting the Outside World – Networking
Network connectivity
Third-party libraries
Summary
10
Developing a Simple To-Do List App
Developing a Simple To-Do List App
Creating the project
Building your UI
Adding functionality to the user interface 
Summary
11
Persisting with Databases
Persisting with Databases
Introduction to databases
Summary
12
Setting Reminders for Tasks
Setting Reminders for Tasks
AlarmManager
Firebase Cloud Messaging
Summary
13
Testing and Continuous Integration
Testing and Continuous Integration
Testing
Stages of testing
Summary
14
Making Your App Available to the World
Making Your App Available to the World
Key store generation
Publishing the app in Google Play Store
Publishing the app in Amazon Appstore
Summary
15
Building an App Using the Google Faces API
Building an App Using the Google Faces API
Introduction to Mobile Vision
Summary
Other Books You May Enjoy
Other Books You May Enjoy
Leave a review - let other readers know what you think
Index
Index

Understanding the code

We could successfully run the app, and now it is time to delve deeper into the code and understand how it works.

Let's start with the MapsActivity.kt Kotlin class file.

The MapActivity class extends the AppCompatActivity class and also implements the OnMapReadCallback interface. We have a couple of variables, GoogleMap, mMap and btnbutton initialized.

Overriding the onCreate method, the app is set to load the content from the XML file, activity_maps.xml, as and when the app is launched.

The resources for the mapFragment and btn are set from the resources file:

class MapsActivity : AppCompatActivity(), OnMapReadyCallback {

private lateinit var mMap: GoogleMap

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_maps)
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
val mapFragment = supportFragmentManager
.findFragmentById(R.id.map) as SupportMapFragment
   ...
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