What you need to build an Android app
Building an Android app requires three things: Android Studio (the official development environment from Google), the Android SDK (software development kit — the tools and libraries that let you write Android code), and a programming language. Most Android apps today are written in Kotlin, which Google now recommends over Java. You do not need to pay for any of these; they are all free.
Your computer needs to run Windows, macOS, or Linux. Android Studio itself takes up about 4 to 6 gigabytes of disk space once fully installed. If you have less than 8 gigabytes of RAM total, your computer will be slow but can still work. You also need a way to test your app — either an Android phone connected by USB cable, or the built-in emulator that comes with Android Studio, which simulates a phone on your screen.
Before you start, decide what your app will do. A simple first app might be a calculator, a to-do list, or a weather display. Avoid trying to build something complex like a social network or a game with graphics; those require skills you will build later. The simpler your first project, the faster you will learn whether app development is something you want to continue.
Key Takeaways
- Download Android Studio from Google's official website, install it, and let it download the Android SDK — this is the only setup you need before you can start coding.
- Kotlin is the language Google recommends for new Android apps, and Android Studio includes templates that generate starter code so you do not begin from a blank screen.
- Test your app on a real Android phone connected by USB, or use the built-in emulator if you do not have a phone; both show you exactly how your app behaves.
- Your first app should be small and focused — a single screen with a few buttons or text fields — so you can finish it and understand the full cycle from code to working app.
- Android apps are built in projects; each project is a folder containing all your code, images, and configuration files, and you open the whole folder in Android Studio.
Installing Android Studio and the SDK
Go to developer.android.com/studio and download Android Studio for your operating system. Run the installer and follow the prompts. When the installer asks whether to download the Android SDK, say yes — this is the collection of tools and libraries you need to build Android apps. The download is large (several gigabytes) and may take 10 to 30 minutes depending on your internet speed.
After installation finishes, open Android Studio. The first time you launch it, you will see a welcome screen. Click "Create a New Project" to start. Android Studio will show you a list of templates — pre-built starter projects for common app types. For your first app, choose "Empty Activity," which gives you a blank screen and basic code structure. Name your project something simple like "MyFirstApp" and choose Kotlin as the language.
Android Studio will generate a folder with all the files your app needs. This folder is your project. Inside it, you will find a folder called app, and inside that, a folder called java or kotlin where your code lives. You do not need to understand every file yet; Android Studio created them so you can focus on writing the parts that make your app unique.
Understanding the basic structure of an Android app
Every Android app has at least one Activity, which is a single screen the user sees. When you open an app and see a screen with buttons and text, that screen is an Activity. Most apps have multiple Activities — one for the home screen, one for settings, one for viewing details — and the user taps buttons to move between them.
Each Activity has two parts: the layout (what the screen looks like) and the code (what happens when the user taps a button or enters text). The layout is written in XML, a markup language similar to HTML. You do not write XML by hand; Android Studio has a visual editor where you drag buttons and text fields onto the screen, and it generates the XML for you. The code is written in Kotlin, and it responds to user actions.
When you create a new project with the Empty Activity template, Android Studio creates one Activity for you, already connected to a layout. The layout file is called activity_main.xml and the code file is called MainActivity.kt. These are the files you will edit to build your first working app.
Building your first screen with the layout editor
Open the file activity_main.xml in Android Studio. You will see a visual editor showing a phone screen. This is where you design what your app looks like. On the left side of the screen, you will see a panel called "Palette" with widgets — buttons, text fields, images, and other things users interact with.
Drag a Button widget from the Palette onto the phone screen. You will see a button appear. Drag a TextView (which displays text) onto the screen as well. In the panel on the right, you can change the text that appears on the button, its size, its color, and where it sits on the screen. Give your button a clear label like "Click Me" or "Calculate." Give your TextView a starting message like "Hello, World!"
Do not worry about making it beautiful yet. The goal is to get something on the screen that you can interact with. Once your button and text are placed, save the file. Android Studio will automatically update the XML code that describes your layout.
Writing code to respond to button taps
Now open MainActivity.kt. You will see Kotlin code that looks like this:
class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) } }
This code creates your Activity and tells it to display the layout you just designed. Now you need to add code that responds when the user taps your button. Inside the onCreate function, after the line that says setContentView, add code to find your button and listen for taps. In Kotlin, it looks like this:
val myButton = findViewById<Button>(R.id.button) myButton.setOnClickListener { val myText = findViewById<TextView>(R.id.textview) myText.text = "You tapped the button!" }
This code finds your button by its ID (which Android Studio assigned automatically), and when the user taps it, it changes the text in your TextView. The ID names come from your layout file; if your button or text view has a different ID, use that name instead. Save the file after you add this code.
Testing your app on a phone or emulator
To see your app running, you need to test it. You have two options: connect a real Android phone by USB cable, or use the emulator built into Android Studio.
Using a real phone: Plug your Android phone into your computer with a USB cable. On your phone, go to Settings, then About Phone, and tap "Build Number" seven times. This unlocks Developer Options. Go back to Settings, find Developer Options, and turn on "USB Debugging." Your phone will ask permission to allow debugging; tap Allow. Android Studio will detect your phone automatically.
Using the emulator: In Android Studio, go to Tools, then Device Manager, and click "Create Device." Choose a phone model and Android version, then click Create. Android Studio will download the emulator software (this takes a few minutes the first time). Once it finishes, the emulator will appear in the Device Manager. Click the play button next to it to start it. A simulated phone screen will open on your computer.
Once your phone or emulator is ready, click the green play button at the top of Android Studio. Android Studio will compile your code, send it to your phone or emulator, and launch your app. You will see your button and text on the screen. Tap the button and watch the text change. If something goes wrong, Android Studio will show error messages at the bottom of the screen; read them carefully, as they usually tell you exactly what went wrong and where.
Common mistakes and how to fix them
The most common mistake is a mismatch between the ID you use in your code and the ID in your layout. If you write findViewById<Button>(R.id.myButton) but your button in the layout is actually called button2, your app will crash. To fix this, open your layout file, click your button, and look at the ID field in the right panel. Use that exact name in your code.
Another common issue is forgetting to import the libraries you need. If you use Button or TextView in your code but Android Studio shows a red underline, click the red underline and select "Import." Android Studio will add the necessary import statement at the top of your file.
If your app compiles but does not appear on your phone or emulator, make sure your phone is actually connected and USB Debugging is on. In Android Studio, go to Tools, then Device Manager, and check that your device is listed and shows "Online." If it shows "Offline," unplug and replug the USB cable.
What to learn next after your first app
Once you have a working button that changes text, you have completed the core cycle: design a layout, write code to respond to user actions, and test it. From here, you can expand in several directions. Learn to use multiple Activities so your app has more than one screen. Learn to save data so your app remembers information between sessions. Learn to fetch data from the internet so your app can display live information like weather or news.
Google's official Android documentation at developer.android.com has tutorials for all of these topics, and they include working code you can copy and modify. The Android community also maintains many free courses and video tutorials. The key is to build small projects that each teach you one new skill, rather than trying to learn everything at once.
Frequently Asked Questions
Do I need to know how to code before I start building Android apps?
You should have basic programming knowledge — understanding what variables, loops, and functions are. If you have never coded before, spend a week learning the basics of Kotlin or Java first. Google's Kotlin documentation has a beginner section, and many free online courses teach programming fundamentals in a few hours.
Can I build an Android app on a Mac?
Yes. Android Studio runs on macOS, Windows, and Linux. The process is identical on all three. Download Android Studio from developer.android.com/studio, choose the version for your operating system, and follow the same steps.
What is the difference between Kotlin and Java for Android?
Both languages work for Android, but Google now recommends Kotlin for new projects because it is simpler to read and requires less code. If you learn Kotlin first, you can learn Java later if you need to maintain older apps. For your first app, choose Kotlin.
How do I put my app on the Google Play Store?
You need to create a Google Play Developer account (which costs a one-time fee of $25), sign your app with a digital certificate, and upload it through the Google Play Console. This is a separate process from building the app itself. Build and test your app thoroughly before you worry about publishing it.
Can I build an app without Android Studio?
Technically yes, but Android Studio is the official tool and makes development much faster. Other editors exist, but they require more manual setup and do not include the visual layout editor or built-in emulator. Start with Android Studio; you can explore alternatives later if you want to.