Book Image

How to Build Android Apps with Kotlin

By : Alex Forrester, Eran Boudjnah, Alexandru Dumbravan, Jomar Tigcal
Book Image

How to Build Android Apps with Kotlin

By: Alex Forrester, Eran Boudjnah, Alexandru Dumbravan, Jomar Tigcal

Overview of this book

Are you keen to get started building Android 11 apps, but don’t know where to start? How to Build Android Apps with Kotlin is a comprehensive guide that will help kick-start your Android development practice. This book starts with the fundamentals of app development, enabling you to utilize Android Studio and Kotlin to get started building Android projects. You'll learn how to create apps and run them on virtual devices through guided exercises. Progressing through the chapters, you'll delve into Android’s RecyclerView to make the most of lists, images, and maps, and see how to fetch data from a web service. Moving ahead, you'll get to grips with testing, learn how to keep your architecture clean, understand how to persist data, and gain basic knowledge of the dependency injection pattern. Finally, you'll see how to publish your apps on the Google Play store. You'll work on realistic projects that are split up into bitesize exercises and activities, allowing you to challenge yourself in an enjoyable and attainable way. You'll build apps to create quizzes, read news articles, check weather reports, store recipes, retrieve movie information, and remind you where you parked your car. By the end of this book, you'll have the skills and confidence to build your own creative Android applications using Kotlin.

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Table of Contents (17 chapters)
Preface
About the Book
1
1. Creating Your First App
1. Creating Your First App
Introduction
Creating an Android Project with Android Studio
Setting Up a Virtual Device and Running Your App
The Android Manifest
Using Gradle to Build, Configure, and Manage App Dependencies
Android Application Structure
Summary
Free Chapter
2
2. Building User Screen Flows
2. Building User Screen Flows
Introduction
The Activity Lifecycle
Saving and Restoring the Activity State
Activity Interaction with Intents
Intents, Tasks, and Launch Modes
Summary
3
3. Developing the UI with Fragments
3. Developing the UI with Fragments
Introduction
The Fragment Lifecycle
Static Fragments and Dual-Pane Layouts
Dynamic Fragments
Jetpack Navigation
Summary
4
4. Building App Navigation
4. Building App Navigation
Introduction
Navigation Overview
Navigation Drawer
Bottom Navigation
Tabbed Navigation
Summary
5
5. Essential Libraries: Retrofit, Moshi, and Glide
5. Essential Libraries: Retrofit, Moshi, and Glide
Introduction
Fetching Data from a Network Endpoint
Parsing a JSON Response
Loading Images from a Remote URL
Summary
6
6. RecyclerView
6. RecyclerView
Introduction
Adding RecyclerView to Our Layout
Populating the RecyclerView
Responding to Clicks in RecyclerView
Supporting Different Item Types
Swiping to Remove Items
Adding Items Interactively
Summary
7
7. Android Permissions and Google Maps
7. Android Permissions and Google Maps
Introduction
Requesting Permissions from the User
Showing a Map of the User's Location
Map Clicks and Custom Markers
Summary
8
8. Services, WorkManager, and Notifications
8. Services, WorkManager, and Notifications
Introduction
Starting a Background Task Using WorkManager
Background Operations Noticeable to the User – Using a Foreground Service
Summary
9
9. Unit Tests and Integration Tests with JUnit, Mockito, and Espresso
9. Unit Tests and Integration Tests with JUnit, Mockito, and Espresso
Introduction
JUnit
Android Studio Testing Tips
Mockito
Integration Tests
UI Tests
Test-Driven Development
Summary
10
10. Android Architecture Components
10. Android Architecture Components
Introduction
ViewModel and LiveData
Room
Customizing Life Cycles
Summary
11
11. Persisting Data
11. Persisting Data
Introduction
Repository
Preferences
Files
Scoped Storage
Summary
12
12. Dependency Injection with Dagger and Koin
12. Dependency Injection with Dagger and Koin
Introduction
Manual DI
Dagger
Koin
Summary
13
13. RxJava and Coroutines
13. RxJava and Coroutines
Introduction
RxJava
Coroutines
Transforming LiveData
Coroutines Channels and Flows
RxJava versus Coroutines
Summary
14
14. Architecture Patterns
14. Architecture Patterns
Introduction
MVVM
Data Binding
Retrofit and Moshi
The Repository Pattern
WorkManager
Summary
15
15. Animations and Transitions with CoordinatorLayout and MotionLayout
15. Animations and Transitions with CoordinatorLayout and MotionLayout
Introduction
Activity Transitions
Animations with CoordinatorLayout
Animations with MotionLayout
Summary
16
16. Launching Your App on Google Play
16. Launching Your App on Google Play
Introduction
Preparing Your Apps for Release
Creating a Developer Account
Uploading an App to Google Play
Managing App Releases
Summary

Parsing a JSON Response

Now that we have successfully retrieved a JSON response from an API, it is time to learn how to use the data we have obtained. To do so, we need to parse the JSON payload. This is because the payload is a plain string representing the data object, and we are interested in specific properties of that object. If you look closely at Figure 5.2, you may notice that the JSON contains breed information, an image URL, and some other bits of information. However, for our code to use that information, first we have to extract it.

As mentioned in the introduction, multiple libraries exist that will parse a JSON payload for us. The most popular ones are Google's GSON (https://github.com/google/gson) and, more recently, Square's Moshi (https://github.com/square/moshi). Moshi is very lightweight, which is why we have chosen to use it in this chapter.

What do JSON libraries do? Basically, they help us convert data classes into JSON strings (serialization)...

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