The Complete Guide to Android App Development in 2026

The usage of mobile phones has skyrocketed with the emergence of smartphones. Smartphones have changed the way we consume content, do business, and go about our daily lives. 85% of the smartphones run on Android, as a result, building an android apps are a prerequisite for any online business worth its salt. This has led to the Google Playstore being flooded by thousands of apps every day. Everything from ordering food, taking a cab, finding employment or entertainment is now just a few clicks away. While hiring an app development agency or company can be a quick way to get to apps, if you have the drive to learn Android App Development, you can develop any number of apps yourself.

In this guide, we will explore how to build an Android app from scratch. This guide is divided into the following sections:

Introduction To Android

About 2.5 billion devices run on the Android operating system. Phones, Televisions, Tablets, Cameras, Game consoles, Car systems, and Smart wearables are some of the device types powered by Android. Hardware configurations of android devices differ from one device to another, but an android operating system provides support for common features such as storage, cameras, connectivity, messaging, and more.

Through the Android platform, Android devices provide notable features, some of them include: Widgets-allows access of information at a glance on the home screen, such as weather information; Custom ROMs-a feature that allows modification/customization of android operating systems to suit one’s interest; and QR code reader are some of the common features.

Getting Started On Your Android App Development Journey

Introduction to Android Application Development

Android app development refers to the creation of an android-based mobile application for your business. As an Android app developer your basic toolkit should include proficiency in Java and C++. It is a basic requirement for getting into android mobile app development.

To get started as an Android developer Android provides the following software toolkits for Android app development:

SDK provides tools to create, debug, and emulate an application. IDE provides a GUI for SDK tools access and an interface to write codes.Android Studio is the preferred IDE.SDK packages come bundled up in Android Studio inform of SDK Manager. JDK is installed on your computer; it provides an interpretation of the Java program.

Programming Languages for Android Application Development

Android Apps can be written in different programming languages (PL). The choice of a language depends on the level of your skillset in different programming languages; strengths and weaknesses of each PL; and more importantly, what you are trying to achieve with your app.

Some of the languages to build Android Mobile Application:

Java: Android applications are officially developed in Java Language. Java is freely available, secure and user-friendly.

Kotlin: Recently added as, among the official language for Android App development by Google, Kotlin is cross-platform and can interoperate with Java through Java Virtual Machine(JVM).

C/C++: Android through Native Development Kit (NDK) allows development in other indigenous languages such as C and C++. This language is more complicated though.

HTML, CSS, and JavaScript: This can be achieved through the Adobe PhoneGap framework. PhoneGap offers a platform to create an app in web-based languages that run on "WebView."

Android Mobile App Development Bundles

An Android Application Kit (APK) is a file that contains all the components required for your android app to execute. Components contained in an APK file are your written code library and resources like images, languages, and screen size binaries.

Before Android OS 5, an android app could only have one APK, subsequent Android versions support multiple APKs within a single app. Generation of multiple APKs was an inconvenience for developers, Android, therefore, came up with Android Application Development Bundle. This feature is available in Android Studio 3.2 and subsequent versions. It is a recently added upload feature that involves auto generation and the signing of app’s APK files.

You build a mobile app in Android Studio, creating an app bundle in the process. Once you have uploaded your app to Google Play; Dynamic Delivery uses the app bundle you created to automatically generate, sign and serve optimized APK files to your app users as per their device configurations.

Some of the advantages of Android App Bundle system are:

Learn To Create An Android App From Scratch

In this section, we discuss the process of creating an android app from the ground up. Let us start with a simple task; go over to Android Studio, write a code in Java to display ‘Hello Android Studio.' Afterward, build a GUI interface that accepts textual input and displays the text.

Fundamental Concepts

Foremost, there are two essential conceptions a novice android app developer must understand; the workings of the android app's components and adaptation of your app to different devices.

Android App’s Components

An Android App is made of loosely coupled components that are separately and independently invoked but interoperate within the app ecosystem. App’s AndroidManifest.xml file contains essential information about each component, how they interact, and their hardware configurations, for example. There are four main components:

Android App’s Device Compatibility

Android Studio provides tools and environment to build an application that can be successfully used in different kinds of android devices. This is done through the type of resources offered. For example, you must provide a resource that allows your application to adapt to different screen sizes, or display in multiple languages. The system decides the kind of resources required based on its hardware specifications.

If your Android application requires specific hardware (like a camera) for it to successfully execute, build it to enquire for the hardware’s availability during runtime, and maybe terminate the execution if the hardware is unavailable. The same goes to permission to access particular information stored in the system or other applications; build your application to request permission, either during runtime or installation. For more on device compatibility, visit Android’s Device compatibility overview.

Steps to Create an Android Project

If you want to build an Android application, you must be ready to invest your resources to ensure your project becomes a success.

As a developer, before installing the Android studio, ensure that your system meets the following minimum requirements.

Minimum System Requirements for Android Studio

Setting up Android App Development Environment

• Download and Install Java Development Kit and Android Studio.
• Download the rest of SDK components inside SDK Manager in the Android Studio.

Steps for developing a new Android Studio project

• Open Android Studio, on its welcoming home page, click on Start a new Android Studio project.

• After that, you will see “New Project Android Studio”. Enter the “Application Name” and the “Company Domain” on their respective text boxes, now click Next.

N/B: “Company Domain” uniquely identifies the application name. Additionally, “Company Domain” is written in reverse, for example, ‘com.mynewapp’.

• “Target Android Devices” appears on the next screen. Select the form factors your app will run on. Below every option, there is a must filled field on “Minimum SDK”. Click Next.

N/B: Refer to “Help me choose” link below the Phone/Tablet selection for more guidelines on the minimum SDK requirement.

On the next page, there is “Add an activity to Mobile”. Select Empty Activity. Activity is based on what you are trying to achieve. Examples of Activities on display are; login, scrolling and empty. Click Next .

The next window that appears is titled “Configure your project”. Complete the following:

After some time, Android main window appears. Now go to View > Tool Windows > Project and review if all the following files are available:

app > java > com.mynewtapp > MainActivity: This is the entry point to your application. After your application is installed and run, the system triggers this Activity.

app > res > layout > activity_main.xml: The XML file dictates the UI layout of your application.

app > manifests > AndroidManifest.xml: Manifest file contains descriptions of your app’s components.

Gradle Scripts > build.gradle: Two files are contained here; one for the project and the other for app module. App module is used to create builds.

Running an Android App

After creating your first Android App, it is time to test your app by running. This section describes how you can run your android application; on a real device and on an emulator.

Testing the app on a Real Device or an Emulator

Connect your phone device to your computer system you have used to develop your app. You have to enable a phone setting called “USB Debugging” for you to run an app on your phone. Here is how to:

Your phone device is now ready to run your android application. Now, open Android Studio and follow the following steps to test your app.

And that’s it! Your phone should be able to display what you had coded to be displayed during development.

Running on an Emulator

Android Studio provides a tool for creation and running of an app emulator. It is done through Android Virtual Device (AVD).Following are guidelines one can refer in creating one:

Now that you have prepared a virtual device, it is time to emulate your application. Follow the following steps:

Android Studio installs and runs your application on the virtual device, and you should be able to see the display of what you had coded your app to output.

Using Android Studio Layout Editor to Create a Simple UI

As a developer, your obligation is not only to code a fully functional application, but must also address the physical layout of your application in order to appease the user. A good app, apart from device compatibility and functionalities, must have a user friendly user interface. In this part, we review how to build a basic textual form that accepts input and send it to another activity by use of an Android Studio Layout Editor.

Let us start off with two definitions here:

User interface is made of Layouts and Widgets.

Layouts are ViewGroup entities that define how child views are placed on an android device screen. Widgets are Views that interact with the user, a text input area being an example.

Now, here are steps on how to build a User Interface (UI) with a text box and button.

This is how your Layout Editor looks like

Add a text box

To add a text box, follow the steps below:

• First, click TextView to delete what is contained in the layout.
• Click Text in the Palette to reveal the existing text controls.
• Click the Plain Text control bar (text editor widget) and drag it to the design editor.
• Resize the view using the square handles by clicking on the design editor.
• Create a right side constraint by dragging the anchor on the top side until it snaps. Creating a constraint helps to restrict the view within the default margins.

Add a button

• Click Buttons on the Palette panel.
• Click the Button widget and drag it into the design editor. Place it after the text widget on the right side.
• Using the steps above, create a constraint from the right side.

Change the UI strings

Use the following steps to adjust the UI strings:

• Open the Project window and click app > res > values > strings.xml.
• Open the Translations Editor by clicking the Open Editor tab. The Translation Editor helps you to edit the default settings.
• To create a new string, click Add Key to create a new string on the text box.
• On the edit_message change the message and add Enter a message as the default value. Then click OK.

Follow the steps below to edit the button UI string.

• Click the text box in the layout.
• Delete the default Name value on the Text property.
• On the right side of the text box, click hint and click Pick a Resource. Then double click on the edit_message.
• Locate the Text property by set as Button, then click Pick a Resource-> button_send.
• Click Apply Changes
• Now you can click Run to install your app and run it.

Components Of Android Software Development

As earlier stated, an Android app is made of components that dependently and independently respond to a user’s needs. This section discusses the types and activation of components and manifest file.

Types of Components

There are four main components:

• Activity - This is the presentation layer of an android application. They dictate the GUI and user interaction with the GUI. Illustratively, an email application can have one activity for sign-in/signup, another one for reading emails, and another for composing a new email. Additionally, activity keeps track of what 's currently on display and previously visited activities.
• Services - This is a backend operating component that manages operations long-running in the background. For example, service may be playing music in the background while the user is engaging a different application on the foreground or retrieving/sending information over the internet while the user is interacting with a separate app.
• Broadcast Receivers - This is an event-driven component, also known as Intent listeners. They listen and receive broadcasts, either from the system or other applications; they then act according to the triggers set in the broadcast. Examples are alarm sets and reminders.
• Content Providers - As the name suggests, they avail content stored in the file system, databases, or other applications. They act as a bridge between data and an app. For example, a media player application accesses music stored in phone storage through its content provider.

Component Activation

Objects managing Component Activation

Your app’s Activity, Services, and Broadcast Receivers’ components are activated by Intent.

Intent is your Android App’s messaging object that provides a platform for applications to call for functionalities from other components. It enables you as a user to engage other components within and outside the application.

For activities and services, Intent manages requests and dictates how those requests are served. For example, an intent may convey a request to an activity to open a URL. An activity represents a single screen on the app and can be initiated by StartActivity().

Intent also provides a value passing mechanism between activities; for example, an activity from your application can request for a photo from activity of another app managing photos.

For a Broadcast Receiver, an Intent can simply decide the message to be broadcasted. For example, an Intent pushing for a new email notification from your email app.

Android supports two types of Intents:

• Implicit Intent only defines an action or data that a particular component requires from other components; the request is passed along to Android System which in turn evaluates and return registered components responsible for the requested action/data.
• Explicit Intent explicitly defines the component responsible for action/data it is requesting.

Content Provider component, on the other hand, is activated by an Android Object called ContentResolver. The ContentResolver is an object that acts as an intermediary between two communicating Content provider components.

Methods by which Components are activated

• Activity: An activity can be activated by passing a method startActivity (Intent)
• Service: You start service through startService (Intent).
• Broadcast Receiver: You can initiate a broadcast by sendBroadcast (Intent).
• Content Provider: You can query a Content Provider by calling query () to a ContentResolver.

Manifest File

For Android System to engage any of your application’s component, it has to be aware of the existence of the component, its functionalities and hardware specifications. All this information about your app's components is stored in a file called Manifest (AndroidManifest.xml).

This file should be located at the root of your project. The file also contains metadata of your app’s components; including themes and icons.

Roles of a Manifest file are as follows:

• It describes the type of components your application is composed of. Besides; it details the functionalities of these components, together with the kind of classes that implements them.
• It declares permissions your app must be afforded. Furthermore, it states permissions other components must have to access your app’s components.
• Declares the minimum level of Android API your app must have.
• Declares your app’s hardware and software requirements; for example, a camera.

Declaring Components and their Capabilities

Declaring Components

The essential purpose of your Manifest file is to declare your app’s components. Any component included in your app but not declared in the Manifest file will be at the bottom of this guide?

If not, we will have to interlink to iOS not be recognized, hence cannot be executed. Let us look at an example; the following is a short excerpt code from an activity declaration Manifest file, and below it is a brief description of different XML tags appearing in this code.

Declaring Components Capabilities

Among the declarations you create in your app’s Manifest file is the declaration of Intent Filters. Intent Filters are the description of intents your app's components would like to work with. When you declare an implicit Intent, the Android System sorts through the Manifest files of registered components, looking to march your declared Intent with Intent filters declared in other components. The Android System launches the component after it finds a march of intents.

Declaring App Requirements

As stated earlier in this article, there are billions of Android devices with different software and hardware specifications. One of the declarations you make in the Manifest file is device specifications. You describe software and hardware features your application requires for it to install and run successfully. When a user goes to Google Play to search for an app, Google Play filters applications and only return those applications whose declared device specifications conform with the user's device.

For example, if your application requires a camera to function, you must make a Manifest File declaration as shown by a code excerpt below.

With the kind of declaration above, Google Play prevents any device with no camera to install your app. You can declare a hardware/software specification as recommended, but not required; in this case, you set the required attribute to false.

Privacy and App Permissions

At the core of the user's app’s consumption is privacy. An Android App user’s privacy is protected by Android’s permission feature. A user’s sensitive information (such as contact list and messages) and device functionality (such as a camera) are protected through permission. Your app, in installation or runtime, must seek permission from the user to access these features.

By default, your application is not permitted to operate in a manner that destructively impacts user’s information, device system and other applications. For example; it is not permissible for your app to read/write user's and other app's information, or manipulate a device's operating system. You can learn more about the app's permissions here.

App’s Permission Declaration

You must declare permissions your application requires in the Manifest file. Permissions are declared through <uses-permission> element. Permissions are applied using Android:permission attribute. For example; you build a dangerous declaration like the one below if your application requires permission to send an SMS.

Types of Permissions

Components Enforcement of Permissions

Permission enforcement differs according to your app’s components.

Check and Request for Permission

As a developer, you build your app to check whether it has permission to access features and data from the device or other applications. You invoke ContextCompat.checkSelfPermission() method to check for permission. The following Kotlin code except checks whether an app’s activity has a right to write to the calendar.

The invoked method returns PERMISSION_GRANTED if your app automatically has permission; otherwise, PERMISSION_DENIED is returned. You can query the user for permission by invoking requestPermissions(). This method, if successfully executed, brings up a prompt box that requests a user to grant permission. In some instances, it is advisable to provide reasons why your app needs permission. For more information on App permissions, check out Permissions overview and App permissions best practices.

Best Mobile App Development Practices for Android

There are a few best practices to be followed in Android App Development to ensure your apps are seamless in their user experience and blow the competition out of the water. While some of the best Android App Development Companies follow these practices, not everyone out there does. So ensure you keep these practices in mind

Dependency Injection

Dependency is a common characteristic in programming. Classes interoperate, referencing each other within their ecosystem. Dependency injection is a concept in which an app's classes are provided with dependencies rather than creating them themselves. Dependencies are initialized elsewhere and passed on to the classes that require them. Dependency Injection happens in two ways

MainActivityRepo is a dependency initialized elsewhere and passed on to the inMainActivitySample class.

Testing

Testing in App development is one of the core stages. Testing happens before deployment and during use. Employing a modular architectural approach is advisable when building an Android app. With this approach, you separate coding blocks according to the tasks they perform, making testing easier because you are working on a few lines of code at a time.

Setting a Testing Environment

The following are best practices in setting up a testing environment.

Noting down Evaluative Tests

After you have set up a testing environment, write down tests that you can use to evaluate your application. The following are three categories of tests you can use:

Testing up the ladder from small to large tests offers the ability to debug efficiently. Kindly refer to these resources at Android testing samples and Android Testing Codelab for more information on testing and Android app.

Accessibility

As a developer, you are encouraged to build an app that everyone can interact with. Users with visual, hearing, and other disabilities should be considered when developing an Android app. The development guidelines to help you create an easy-to-use Android app are as follows: