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This chapter is an introduction to Android, where you will set up the Android Studio environment and focus on the fundamentals of Android development.You will cover creating an Android project with Android Studio. Then, you will set up a virtual device and run your app on it. You will explore the Android manifest file, which details all the Android app components, features and permissions model. You will learn how to use the Gradle build system and analyze the Android application structure. You will start developing user interfaces (UIs) with the Android UI toolkit, Jetpack Compose.By the end of this chapter, you will have gained the knowledge required to create an Android app from scratch and install it on a virtual Android device. You will be able to analyze and understand the importance of the AndroidManifest.xml file. You will learn how an app project is structured in Android Studio and use...

Technical requirements

The complete code for all the exercises and the activity in this chapter is available on GitHub at https://github.com/PacktPublishing/How-to-Build-Android-Apps-with-Kotlin-Third-Edition/tree/main/Chapter01.

Creating an Android project with Android Studio

In order to be productive building Android apps, it is essential to become confident with using Android Studio. This is the official integrated development environment (IDE) for Android development, built on JetBrains’ IntelliJ IDEA IDE and developed by the Android Studio team at Google. You will use it throughout this course to create apps and progressively add more advanced features.Since Google I/O 2017 (the annual Google developer conference), Kotlin has been Google’s preferred programming language for Android app development. You will be using Kotlin throughout this book to build Android apps.Kotlin was created to address some of the shortcomings of Java in terms of verbosity, handling null types, and adding more functional programming techniques, amongst many other issues.Getting to grips and familiarizing yourself with Android Studio will enable you to feel confident building Android apps. So, let’...

Setting up a virtual device and running your app

As a part of installing Android Studio, you downloaded and installed the latest Android software development kit (SDK) components. This includes a base emulator, which you will configure to create a virtual device to run Android apps on. An emulator mimics the hardware and software features and configuration of a real device. The benefit is that you can make changes and quickly see them on your desktop while developing your app. Although virtual devices do not have all the features of a real device, the feedback cycle is often quicker than going through the steps of connecting a real device.The screen you will have seen (or something similar) when installing Android Studio is as follows:

Let’s take a look at the SDK components that are installed and how the virtual device fits in:

• Android Emulator: This is the base emulator, which...

The Android manifest file

The app you have just created, although simple, encompasses the core building blocks that you will use in all the projects you create. The app is driven from the AndroidManifest.xml file, a manifest file that details the contents of your app. To open it, locate the tool window by selecting View | Tool Windows | Project. Once displayed, the drop-down options on the top of the Project window allow you to change the way you view your project, with the most commonly used displays being Android and Project:

The AndroidManifest.xml file is located at app | manifests in the Android display of the Project window:

<?xml version="1.0" encoding="utf-8"?>
<manifest
    xmlns:android="
        http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">
    <application...

Using Gradle to build, configure, and manage app dependencies

In the course of creating this project, you have principally used the Android platform SDK. The necessary Android libraries were downloaded when you installed Android Studio. However, these are not the only libraries that are used to create your app. To configure and build your Android project or app, a build tool called Gradle is used.Gradle is a multi-purpose build tool that Android Studio uses to build your app. You can either use Kotlin or Groovy, a dynamically typed Java virtual machine (JVM) language, to configure the build process and allow easy dependency management so you can add libraries to your project and specify the versions.As the default language when creating a new project in Android Studio is Kotlin, you will be using this. The files that this build and configuration information is stored in are named build.gradle.kts, which are Kotlin script files. You benefit from the same autocompletion and...

Android application structure

Now that we have covered how the Gradle build tool works, we’ll explore the rest of the project. The simplest way to do this is to examine the folder structure of the app. Open up the Project tool window.When you select it, you will see a view like the screenshot in Figure 1.17. If you can’t see any window bars on the left-hand side of the screen, then go to the top toolbar and select View | Appearance | Tool Window Bars and make sure it is ticked.Open the corresponding folders in the Android display. This view neatly groups the app folder structure, so let’s look at it:

The Kotlin file (MainActivity), which you’ve specified as running when the app starts, is as follows:

import…
class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
 ...

Summary

This chapter has covered a lot about the foundations of Android development. You started with how to create Android projects using Android Studio and then created and ran apps on a virtual device.The chapter then progressed by exploring the AndroidManifest file, which details the contents of your app and the permission model, followed by an introduction to Gradle and the process of adding dependencies and building your app.This was then followed by going into the details of an Android application and the files and folder structure. Jetpack Compose was introduced, and exercises iterated to illustrate how to construct UIs with an introduction to Google’s Material Design.The next chapter will build on this knowledge by learning about the activity life cycle, activity tasks, and launch modes, persisting and sharing data between screens, and how to create robust user journeys through your app