Creating an Android App with Java in Android Studio

To start, you first need to click on the new project button to start configuring your Android app.

On the first page, you need to select what activity you want to use for creating your app. Since we don’t want any pre-created buttons or menus in this app we are just using the Empty Views Activity.

FYI: An activity is one screen of an app. If you are for example creating an app with a login mechanism you would have the following activities:

• Login Activity
• Registration Activity
• Home Activity

The app would probably start with the login activity. On this activity, you could now have two fields for email and password and two buttons. One for new users which would open the registration activity and one login button which would redirect the user to the home activity.

After pressing next you will see the actual configuration screen of your project. There you can change various settings for your app. You can enter whatever you like regarding the name and the package name. This applies also to the save location. However, if you change the directory, no new folder will be created with the project name so the project gets generated exactly in the folder you choose. So don’t choose a parent folder without creating a subfolder.

For the language you should also choose whatever you know the best. For this tutorial, I am choosing Java. The next point is the minimum SDK. This means any device with an Android version below this version won’t be able to download and use this app. A good minimum SDK is API 24 which is already preselected. Below the drop-down menu, you can also see how many smartphones can use this app. The last configuration option is the build configuration language. You can choose between Kotlin and Groovy and since Kotlin is superior we are choosing it.

After every configuration option is set it should look similar to the screenshot below. If this is the case you can start the generating process of your Android app with Java by clicking Finish.

After your project is generated you should locate two important files in the project explorer on the left of the screen. The MainActivity class contains all the programming logic for our activity. The activity_main.xml file contains the information on how your MainActivity will look like.

When opening the activity_main.xml you will probably see a white screen with a Hello World! text since this is the default option. But there is also an option to see the code of the actual file side by side with the live preview of it which is mandatory for developing an app. To switch to this view click on the symbol in the top right corner highlighted in the screenshot below. You can also see another highlighted button. With that, you can switch from seeing a blueprint beneath the actual preview of the activity to just previewing the activity. For that, you have to switch to Design only.

Extending the Source Code of Your App

Now that you know the basics we are extending the source code of your Android app with Java a bit so there will be a Button that can be pressed which increases a counter that is displayed in a TextView. For this, we are giving the already existing TextView in the activity_main.xml an ID. An ID is needed so we can access the TextView via the logic inside the MainActivity Java class. To add an ID you need to add the line below inside the TextView tag.

android:id="@+id/counterLabel"

After adding this line we are also adding a Button to the activity with this code:

    <Button
        android:id="@+id/countUpButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Count up"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/counterLabel" />

Now our activity_main.xml is done and should look like this:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/counterLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/countUpButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Count up"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/counterLabel" />

</androidx.constraintlayout.widget.ConstraintLayout>

The user interface is now done. There is a Button and a TextView. Now we need to access these two components inside the MainActivity.java and work with them.
First of all, we are adding 3 variables to the class.

• private TextView counterLabel; This will be set to our TextView
• private Button counterButton; This will be set to our Button
• private int currentCount = 0; This will work as our counter variable

Then we initialize the TextView and Button variables. This can be done in the onCreate method since this method is only once called at the very start of the activity. To get different components of your XML files you call findViewById(R.id.<IDInsideXMLFile>). So the assignments will look like this.

counterLabel = findViewById(R.id.counterLabel);
counterButton = findViewById(R.id.countUpButton);

The next step is to set the text of the counter label to 0. For setting an initial value there are always two options. The first one is to set it directly inside the activity_main.xml file with the android:text attribute or you can do it via code like this:

counterLabel.setText(String.valueOf(currentCount));

Last, we need to add an onClickListener with which we can override the onClick method to increase our counter and set the new value to our TextView. To do this you can either use a lambda expression or not. That depends entirely on what you prefer to use. You can see the difference below:

counterButton.setOnClickListener(v -> {
    currentCount++;
    counterLabel.setText(String.valueOf(currentCount));
});

counterButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        currentCount++;
        counterLabel.setText(String.valueOf(currentCount));
    }
});

Finally, your finished MainActivity class will look like this:

package com.example.myfirstandroidapp;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private TextView counterLabel;
    private Button counterButton;
    private int currentCount = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        counterLabel = findViewById(R.id.counterLabel);
        counterButton = findViewById(R.id.countUpButton);

        counterLabel.setText(String.valueOf(currentCount));

        counterButton.setOnClickListener((v) -> {
            currentCount++;
            counterLabel.setText(String.valueOf(currentCount));
        });
    }
}

Always call findViewById after super.onCreate(savedInstanceState); and setContentView(R.layout.activity_main);. Otherwise, it will not work.

Testing Your First Android App with Java

To test your newly created Android app with Java you have two options.
The first one is to use your real mobile phone. You can either connect it via cable or connect via Wi-Fi. To do this you first need to enable the respective debugging mode on your smartphone in the developer settings. This can vary from brand to brand so the best thing is to Google how to do it on your device. After enabling the mode you can connect your device via cable and the smartphone will automatically show up on the devices list, or you use ‘Pair Devices Using Wi-Fi’ from the options in the screenshot below and follow the steps displayed.

The second option to test your Android app with Java is, to use a virtual device. The advantage of a virtual device is, that you can have multiple. So you can test your app on devices with different sizes and Android versions. Furthermore, you can test device categories that you may not even own, like a smartwatch. To learn how to add a virtual device you can click here.

After you have added/selected the correct device you can now click on the play button next to the drop-down list, which is also highlighted in the screenshot below to start your app.

After clicking the button the app will be built. When the build process is finished the virtual device will start and launch your app. If you use your personal device the app will also launch itself. After the application is started on your device it should look like the preview from the activity_main.xml file. To test the logic we implemented you can click on the counter button. You will then see the counter getting increased with each click.

This was the process of creating your first Android app with Java in Android Studio. If you have any problems or questions feel free to comment below. To read more about creating an app in Android Studio you can visit the documentation of Google.

Why You Should Have One or More Virtual Devices

After developing mobile applications you will ask yourself how to test your app. There are two options: The first option is, to load your program on your smartphone. The benefits are clear. Once uploaded on your phone you can show it to friends and family members but there are also downsides. The phone must be either connected via cable or wirelessly. Additionally, debugging has to be enabled in the developer settings. Furthermore, it always has to be nearby and the uploading process often takes quite a long time.

With a virtual device, you don’t need to have your phone always with you to test your mobile applications. You can press ‘Run’ inside Android Studio and a virtual smartphone will be powered up where your app gets deployed. Also with the virtual device, you can simulate different things like a bad internet connection.

Another big advantage is, that you can have multiple virtual devices with different screen sizes and Android versions, which is extremely useful for developing apps, which have to work for older phones and should also look good on foldable phones or phones with rather small displays.

Add a Powerful Virtual Device in Android Studio

To add a powerful virtual device in Android Studio the first thing you need to do is to check if Hyper-V is enabled. To learn how to enable it, you can click here. After you have enabled it, you need to open the device manager in Android Studio. This can be done with the menu on the very right in Android Studio. There you have to click on the icon with a smartphone and the android logo. You can see the location in the screenshot below. After opening it, you have to click on the plus symbol to add a new powerful virtual device in Android Studio.

After clicking on the plus icon, a new dialog will be displayed on your screen. Now the real process to add a powerful virtual device in Android Studio begins. First of all, you have to decide which device you want to create. You can choose from different categories like phones, tablets, watches, or even TVs. In this tutorial, we are using the Google Pixel 8 since the size is rather common. After choosing the device you can confirm your selection with a click on Next.

In the next dialog window, you can choose your desired Android version for your new virtual device in Android Studio. If you have already downloaded the desired version, you can select it and click on next. Otherwise, you have to click on the small download icon next to the Android version name. In this case, I am choosing the newest version, 14.

After pressing on download another window will appear where you must accept the license agreement. Just select Accept and press Next to start downloading the SDK.

The download will take some time. After it is finished you can press the Finish button in the bottom right corner of the download dialog.

After clicking on Finish you will be back at the window where you can choose the desired Android version. You can now select the downloaded version and confirm the selection by pressing Next on the bottom.

After clicking Next you will see the last dialog to create a virtual device in Android Studio. There you will see a quick overview of your selections and you can also give the device a name. I would recommend that you include the API version (Android version) in the name, so you quickly know what version the device is running on. After you have checked your previous selections and named your device you can finish the process to add a virtual device in Android Studio with a click on the Finish button.

Now your device will show up in the device overview of the device manager. You can start the virtual smartphone directly by launching your app with the play icon on the top or you can start the device without starting your mobile application via the play button next to your device inside the device manager.

Problem: Black Circle on the Screen in Addition to the Camera

Sometimes there might be a problem after you’ve added a powerful virtual device to Android Studio – a black circle is displayed on the screen in addition to the camera punch hole. This is because a display cutout is activated in the developer options of the device. To deactivate it you first have to activate the developer options. You can do this by opening the settings on the smartphone, then clicking on ‘About phone’ and scrolling down to ‘Build number’. You have to click on Build number 7 times to enable the developer options. After clicking on it that many times you will see a message on the screen that the developer options are now enabled.

After the activation, you have to go back to the start of the settings. Now scroll down to ‘System’ and open the ‘Developer options’. You now have to search for ‘Display cutout’. The setting is located approximately two-thirds of the way up the menu. After you have found it you can click on it and select ‘Device default’ so only the normal camera punch hole is visible.

Now everything should be working without any problems. If you have any troubles or questions feel free to leave a comment or visit the official documentation of Google.

Hyper-V to Simulate a Virtual Smartphone

The first thing you need to do before you can set up your Android development environment is to enable Hyper-V. This is necessary to run a simulator for a virtual smartphone on your computer. This simulator is used later for testing the Apps you are going to develop. If you do not want to do that, you always have to use a real smartphone to run your developed Apps. So a smartphone simulator will make your developer’s life a lot easier.

To activate Hyper-V you can read our guide on how to Enable Hyper-V on Windows 11 Pro and Unlock Powerful Virtualization.

Android Studio as Android Development Environment

There are many platforms out there, where you can develop Android apps. But the best development environment will be Android Studio. It is built and distributed directly by Google, which also developed Android.

Android Studio has two major benefits:

• It is specifically designed for developing Android apps. So everything necessary is already integrated including the simulated smartphones – so there is no Plugin installation needed.
• Android Studio is built on JetBrains IntelliJ IDEA – so if you are already familiar with IntelliJ you will love Android Studio because the user interface is almost the same.

Downloading and Installing Android Studio

To download Android Studio, you first need to visit the official download site. There you should already see a Download Android Studio button in the middle of the page. When you click on that, a popup for the terms and conditions will pop up. To start the download you have to scroll down on the page, check the checkbox that you have read and agree with the terms and conditions and press Download Android Studio again. Now the download of the setup .exe file will start

After the download is complete, you can open the setup file to start the installation process. The first page you will see looks like the screenshot below. You just have to press Next.

The next window will ask you what components you want to install. There you can already define if you want to install the Android Virtual Device component as well as the Android development environment itself. If you want to use a simulated smartphone make sure that the checkbox next to the Android Virtual Device is checked and confirm your choice by pressing Next.

On the following device, you can choose your installation path. To speed up your program, I would recommend installing it on an SSD.

The next page asks you if you want to put your Android Studio application in a new Start Menu Folder or if you want to add it to an already existing one. You can choose whatever you like, change the name of the new folder, or also mark the checkbox at the bottom to not create a shortcut at all. After you have decided what you want to do, you can click on Install to start the installation process of your Android development environment.

After pressing Install, the setup will start the installation of Android Studio. When the progress bar is full and the text above it states Completed, you can press the Next button on the bottom to open the final setup window.

If you want to setup and start Android Studio right now, you have to mark the checkbox. Otherwise, you can deselect it. Either way, you need to click on Finish to complete the installation process.

Setting up Android Studio

After starting up Android Studio, you will be confronted with the importing of Android Studio settings. If you do not have exported settings from another computer or you have already installed Android Studio previously, you just have to select ‘Do not import settings’ and click on OK.

After pressing OK you will see the dialog from the screenshot below. It is asking you to send usage statistics to Google to help them improve Android Studio in the future. You can decide if you want to do that or not. In this case, I am pressing Don’t send.

On the following Welcome screen of the Android Studio Setup Wizard, you just need to click Next.

The next window asks you for the Installation Type. There you can just select Standard and start the final installation of all necessary things for your Android development environment with a click on Next.

On the following screen, you see a short overview of the things that get installed. If you want to change your installation type you can do that by pressing previous. If you want to continue with the installation click on Next.

After pressing Next the installation of all required components for your Android development environment will start. After finishing you can click Finish to get to the next page.

On this page, you just have to agree to the licenses of your downloaded components. You have to accept each license separately by clicking on it in the left column and selecting Accept in the bottom right corner. After accepting all, you can click Finish.

Now you will see the starting screen of Android Studio your new Android development environment. If you are using already IntelliJ IDEA you will recognize this page already.

If you have any questions regarding the setup process or the installation feel free to reach out to me via the comments or the contact form!