Category: Java Android app development

Hello! In this lecture, we will take a closer look at the necessary environment setup, ‘Installing Android Studio’, before starting Android app development using Java. Android Studio is an integrated development environment (IDE) officially provided by Google, and it is the most commonly used tool for developing Android applications.

What is Android Studio?

Android Studio is a powerful tool for developing Android apps. This IDE provides various features such as templates, code assistants, performance analysis tools, and profilers to help developers work efficiently. Android Studio supports multiple languages, such as Java and Kotlin, and is chosen by numerous developers due to its user-friendly UI and rich functionality.

System Requirements

Before installing Android Studio, you need to ensure that your computer meets the following system requirements.

• Operating System: Windows 10/8/7 (64-bit), macOS 10.14 or later, Linux
• RAM: Minimum 8GB (recommended 16GB or more)
• Disk Space: Minimum 4GB (SSD recommended)
• Monitor Resolution: 1280×800 or higher

Installing Android Studio

Now, let’s learn how to download and install Android Studio. Please follow the steps below.

1. Download Android Studio

To download Android Studio, you need to go to Google’s official website. Click the link below to go to the download page.

Android Studio Download Page

2. Run the Installer

Run the downloaded installer file to start the installation. The following installation steps are required.

1. When the installation wizard starts, click the ‘Next’ button.
2. Read the license agreement and select ‘I Agree’, then click ‘Next’ again.

3. Choose Installation Type

A screen appears where you can select the components to install. You can choose between the two options below:

• Standard: Installs only the basic features.
• Custom: Selects additional features to install.

It is recommended for beginners to choose ‘Standard’. After making your selection, click ‘Next’.

4. SDK Setup

You will be prompted to install the Android SDK (Software Development Kit). In this setup, check the following:

• Confirm SDK path (you can leave it as default)
• Select the required Android API level for SDK components (latest stable version recommended)

Once you’ve completed the setup, click ‘Next’.

5. Finish Installation

When the installation is complete, click the ‘Finish’ button to close the installation wizard. If you check ‘Start Android Studio’, it will automatically launch Android Studio.

First Launch of Android Studio

Now that the installation is complete, let’s launch Android Studio for the first time. When the program runs, a welcome screen will appear as follows:

1. Configuration Settings

In the welcome screen, you can set the following:

• Select UI Theme: Options include Light, Darcula, etc.
• Import Settings: If you have existing settings, you can import them.

If you are starting fresh, you can proceed with the defaults.

2. Starting a Project

In the welcome screen, you can start a new project by clicking ‘Start a new Android Studio project’. Choose a template, and set the project name, package name, and storage path.

Creating a Simple Hello World App

Once the Android Studio installation is complete, let’s create a simple Hello World app. Follow the steps below.

1. Create a New Project

Click the ‘New Project’ option and select the ‘Empty Activity’ template. Enter the project name, select Java as the language, and then click ‘Finish’.

2. Modify the Layout File

Open the ‘res/layout/activity_main.xml’ file in Android Studio and modify it as follows:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/hello_world"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:layout_centerInParent="true"/>

</RelativeLayout>

3. Modify the Java File

Open the ‘MainActivity.java’ file and add the following content:

package com.example.helloworld;

import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

4. Run the App

Once all settings are complete, click the ‘Run’ button to execute the app. You can choose to test the app on an emulator or a physical device. If it runs successfully, the phrase ‘Hello World!’ will be displayed in the center of the screen.

Conclusion

In this lecture, we explained the installation process of Android Studio and how to create a simple Hello World app. We have taken an important step in beginning Android development, and now you have learned the basics of Android app development using Java. In the next lecture, we will cover how to create more complex apps and utilize Java’s features.

Additional Resources

Additional resources for Android app development are as follows:

• Android Developer Docs
• Gradle Documentation
• Stack Overflow

Wishing you success in your Android app development journey!

Android is a mobile operating system (OS) developed by Google, widely used on various devices such as smartphones and tablets. It is an open-source system, allowing developers to freely create applications. This course will provide the basic information needed for developing Android apps using the Java language and will include practical coding examples.

History of Android

Android started in 2003 when Android Inc. was founded, and was acquired by Google in 2005. The first Android device was launched in 2008, and it has since been used on various devices, experiencing rapid growth. It currently occupies about 80% of the global smartphone market, with many developers distributing countless apps through the Android platform.

Android Architecture

The Android architecture is primarily composed of four main layers:

• Linux Kernel Layer: It provides stability and security and connects to the hardware abstraction layer (HAL) of Android and key services.
• Framework Layer: It provides APIs that app developers can access and includes key components such as Activity, Service, Content Provider, and Broadcast Receiver.
• App Layer: This consists of the applications provided to the actual user and includes the user interface (UI) and business logic.
• Manifest File: It defines the app’s metadata and specifies the app’s components, permissions, and hardware requirements.

Setting Up the Development Environment

To develop Android apps, you first need to set up your development environment. The required tools are as follows:

1. Java Development Kit (JDK): This is the software needed to set up the Java environment. It can be downloaded from the Oracle website.
2. Android Studio: This is the Android integrated development environment (IDE) provided by Google. Android Studio offers a range of tools, including a code editor, debugger, and emulator.

After setting up the environment, you can run Android Studio and create a new project.

How to Install Android Studio

1. Download and install the JDK from the Oracle website.
2. Download the installation file from the official Android Studio website.
3. Run the downloaded file and follow the installation process.

Creating a New Project

Run Android Studio, and click “Start a new Android Studio project” to create a new project. The next step is to select a project template and enter the project name and package name. You can also set the minimum supported SDK version during this process.

Basic Concepts of Java-Based Android App Development

Android apps are composed of the following basic components:

• Activity: The basic element that composes the user interface (UI) and constructs the screen.
• Service: Handles tasks that run in the background. It runs without a UI.
• Broadcast Receiver: Receives and processes events occurring from the system or apps.
• Content Provider: Provides a standard interface for data sharing between apps.

Simple Android App Example

Now let’s create a simple ‘Hello World’ app. This app implements the functionality of displaying the text “Hello, World!” when the button is clicked.

MainActivity.java

package com.example.helloworld;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    private TextView textView;
    private Button button;

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

        textView = findViewById(R.id.textView);
        button = findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                textView.setText("Hello, World!");
            }
        });
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Click the button"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="100dp" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Click Me"
        android:layout_below="@id/textView"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="20dp" />

</RelativeLayout>

Running the App

After writing the code, click the “Run” button in the Android Studio menu to execute the app on the emulator. The emulator provides a virtual environment for Android devices, allowing various device configurations to be emulated.

Conclusion

This course introduced the basics of Android app development using Java. We covered the history and architecture of the Android platform, how to set up the development environment, and implemented a simple example app. In future lessons, we will cover more diverse functionalities and explore content that can be applied in practice. Step into the world of Android app development!

1. Introduction

In today’s mobile environment, the Android platform is one of the most widely used operating systems. In particular, using the Java language to develop apps is a familiar approach for many developers. In this course, we will start from the basics of app development through integration with basic Android apps and take it a step further to implement various features. Through this course, you will understand the interaction between Android apps and basic apps (e.g., contacts, camera, etc.) and develop the ability to implement them yourself.

2. Setting Up the Android App Development Environment

To develop Android apps, you first need to set up the development environment. Using Android Studio provides many convenient tools and features. Below are the installation steps for Android Studio.

1. Download Android Studio: Download from the official Google site.
2. Installation: Follow the installation wizard.
3. SDK Installation: The necessary SDKs and tools will be installed automatically.
4. Creating a Project: Click on ‘New Project’ to create a new Android project.

3. Understanding Android Basic Apps

Android has several types of basic apps. These apps provide functionalities that developers can easily use without the need for external libraries. For example, there are contacts apps, camera apps, maps apps, etc. In this section, we will use an example connected to the contacts app to explore the functionalities of basic apps.

4. Integrating with the Contacts App

We will implement a feature that retrieves contact information by integrating with the contacts app. The following are the steps to implement this feature.

4.1. Requesting Permissions

To access the contacts, you need to request permission from the user. Add the following permission to the AndroidManifest.xml file.

                
                <uses-permission android:name="android.permission.READ_CONTACTS" />
                
            

4.2. Retrieving Contact Information

Now, open the MainActivity.java file and write the code to retrieve contact information.

                
                import android.Manifest;
                import android.content.ContentResolver;
                import android.content.pm.PackageManager;
                import android.database.Cursor;
                import android.net.Uri;
                import android.os.Bundle;
                import android.provider.ContactsContract;
                import android.view.View;
                import android.widget.Button;
                import android.widget.TextView;
                import androidx.annotation.NonNull;
                import androidx.appcompat.app.AppCompatActivity;
                import androidx.core.app.ActivityCompat;

                public class MainActivity extends AppCompatActivity {
                    private static final int REQUEST_CODE_CONTACT = 1;
                    private TextView textView;

                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        
                        textView = findViewById(R.id.textView);
                        Button button = findViewById(R.id.button);
                        
                        button.setOnClickListener(new View.OnClickListener() {
                            @Override
                            public void onClick(View view) {
                                checkPermission();
                            }
                        });
                    }

                    private void checkPermission() {
                        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_CONTACTS) != PackageManager.PERMISSION_GRANTED) {
                            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_CONTACTS}, REQUEST_CODE_CONTACT);
                        } else {
                            getContacts();
                        }
                    }

                    private void getContacts() {
                        ContentResolver resolver = getContentResolver();
                        Uri uri = ContactsContract.Contacts.CONTENT_URI;
                        Cursor cursor = resolver.query(uri, null, null, null, null);
                        
                        StringBuilder contactsList = new StringBuilder();
                        
                        while (cursor.moveToNext()) {
                            String name = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME));
                            contactsList.append(name).append("\n");
                        }
                        cursor.close();
                        textView.setText(contactsList.toString());
                    }

                    @Override
                    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
                        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
                        if (requestCode == REQUEST_CODE_CONTACT && grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                            getContacts();
                        }
                    }
                }
                
            

4.3. Building the UI

Open the activity_main.xml file and build the UI. You will add a Button and a TextView by default.

                
                <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:orientation="vertical">
                    <Button
                        android:id="@+id/button"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Get Contacts" />

                    <TextView
                        android:id="@+id/textView"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content" />
                </LinearLayout>
                
            

4.4. Running the App

Now, run the project. When you click the ‘Get Contacts’ button, the list of contacts will be displayed in the TextView. If a permission request dialog appears, you must click allow to retrieve contact information.

5. Integrating with the Camera App

Next, we will implement a feature to take a photo by integrating with the camera app. Integrating with the camera is also a great example of integration between basic apps.

5.1. Requesting Permissions

The method for requesting permissions to access the camera is similar to that of the contacts app. Add the following to the AndroidManifest.xml.

                
                <uses-permission android:name="android.permission.CAMERA" />
                <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
                
            

5.2. Taking a Photo

Add the function for taking a photo in the MainActivity.java file.

                
                import android.content.Intent;
                import android.graphics.Bitmap;
                import android.net.Uri;
                import android.os.Bundle;
                import android.provider.MediaStore;
                import android.widget.Button;
                import android.widget.ImageView;
                import androidx.appcompat.app.AppCompatActivity;

                public class MainActivity extends AppCompatActivity {
                    private static final int REQUEST_IMAGE_CAPTURE = 1;
                    private ImageView imageView;

                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        
                        Button button = findViewById(R.id.button);
                        imageView = findViewById(R.id.imageView);
                        
                        button.setOnClickListener(view -> {
                            Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                            if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
                                startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
                            }
                        });
                    }

                    @Override
                    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
                        super.onActivityResult(requestCode, resultCode, data);
                        if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
                            Bundle extras = data.getExtras();
                            Bitmap imageBitmap = (Bitmap) extras.get("data");
                            imageView.setImageBitmap(imageBitmap);
                        }
                    }
                }
                
            

5.3. Building the UI

Add an ImageView in the activity_main.xml file to display the captured photo.

                
                <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:orientation="vertical">
                    <Button
                        android:id="@+id/button"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Take Photo" />

                    <ImageView
                        android:id="@+id/imageView"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent" />
                </LinearLayout>
                
            

5.4. Running the App

Now run the program and click the ‘Take Photo’ button. If it works correctly, the camera will launch, and after taking the photo, the result will be displayed in the image view.

6. Conclusion

In this course, we learned how to integrate with basic Android apps using Java. Through the integration of contacts and camera apps, we explored how to utilize the functionalities of basic apps in app development. Based on this example, you can expand your own app functionalities and try various forms of integration. Continue to learn and practice Android app development to further your skills!

Hello! In this course, we will explore one of the very important topics in Android app development: how to understand the system status. Understanding system status in Android development is an essential element for optimizing app performance, improving user experience, and debugging. Through this course, we will learn how to collect system information and how to improve the app based on this information.

1. What is system status?

System status refers to various information and attributes that the current device possesses. This includes CPU usage, memory usage, battery status, network status, and more. This information provides important hints about how the app operates and how to manage resources efficiently.

2. Checking system status in Android

In Android, you can check system status through various APIs. In this section, we will learn how to retrieve the main system status information in Android.

2.1. Checking battery status

To check the battery status, you can use the BatteryManager class. Below is an example code for checking the battery status.

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.BatteryManager;

public class BatteryStatusReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        int level = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
        int scale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
        float batteryPct = level / (float)scale * 100;

        // Print remaining battery
        System.out.println("Current battery level: " + batteryPct + "%");
    }
}

The above code creates a receiver that receives the battery status. The onReceive method is called every time the battery status changes, outputting the current battery level. To register this receiver, you can use the following code.

IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
Intent batteryStatus = context.registerReceiver(null, ifilter);

2.2. Checking memory status

To measure memory usage, Android utilizes the ActivityManager class. Here is a code example to check current memory usage.

ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
ActivityManager.MemoryInfo memoryInfo = new ActivityManager.MemoryInfo();
activityManager.getMemoryInfo(memoryInfo);

long totalMem = memoryInfo.totalMem;
long availMem = memoryInfo.availMem;

// Print memory status
System.out.println("Total memory: " + totalMem + " bytes, Available memory: " + availMem + " bytes");

This code outputs the current total memory and available memory. This provides insights into memory management for the app.

2.3. Checking CPU usage

To check CPU usage, you can use methods provided by the Debug class. Here is a simple way to measure CPU usage.

import android.os.Debug;

// Print CPU usage
Debug.MemoryInfo memoryInfo = new Debug.MemoryInfo();
Debug.getMemoryInfo(memoryInfo);

int totalPss = memoryInfo.getTotalPss();
System.out.println("Total PSS: " + totalPss + " KB");

Through this, you can get information about the current app’s memory usage and CPU usage, contributing to performance optimization.

3. Optimizing resource usage based on system status

After understanding the system status, you can optimize the app’s resource usage based on this. Here are a few optimization methods.

3.1. Appropriate process termination

When the system memory is low, you can ensure system stability by terminating unnecessary processes. You can manage running processes using ActivityManager.

activityManager.killBackgroundProcesses("com.example.app");

3.2. Optimizing battery usage

To minimize battery usage, it is essential to adjust the frequency of background tasks appropriately and stop unnecessary tasks. For example, you can reduce network requests to a minimum or adjust to not use GPS continuously.

3.3. Providing notifications to users

By providing notifications to users based on system status, you can improve the user experience. For example, if the battery level falls below a certain threshold, you can notify the user about switching to battery-saving mode.

if (batteryPct < 20) {
    // Notify the user about battery-saving mode
}

4. Summary

In this course, we learned how to understand system status in Android app development and techniques for optimizing resources based on this understanding. We covered various methods to monitor battery, memory, CPU usage, etc., to enhance app performance and improve user experience. Developing apps based on this system information will lead to more stable and efficient applications.

Now you have the ability to create better apps by understanding and optimizing system status in Android app development. If you have further questions or want to cover more in-depth topics, we recommend referring to additional materials. Thank you!

For modern smartphone users, a clock app is an indispensable tool.
Consequently, many developers are creating clock apps and adding various features.
In this tutorial, we will explore in detail how to implement a stopwatch function while developing an Android app using Java.

1. Setting Up the Development Environment

To develop a stopwatch app, you need Android Studio and a Java development environment.
Follow the steps below to set up the development environment.

1. Download and Install Android Studio:
   Android Studio is the officially supported Android development tool.
   Download the latest version from the [Android Studio Download Page](https://developer.android.com/studio) and install it.
2. Create a New Project:
   Launch Android Studio and select “New Project,” then choose “Empty Activity.”
   Set the project name to “StopwatchApp” and select Java.
3. Gradle Setup:
   Use Gradle builds to add the necessary libraries and set the SDK version.
   Set `compileSdkVersion` and `targetSdkVersion` appropriately in the `build.gradle` file.

2. Designing the UI

Now, let’s design the UI of the stopwatch. In Android, we define layouts using XML.
Open the `activity_main.xml` file and write the code as shown below.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/txtTimer"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="00:00:00"
        android:textSize="48sp"
        android:layout_centerInParent="true"/>

    <Button
        android:id="@+id/btnStart"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Start"
        android:layout_below="@id/txtTimer"
        android:layout_marginTop="20dp"
        android:layout_alignParentStart="true"/>

    <Button
        android:id="@+id/btnStop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Stop"
        android:layout_below="@id/txtTimer"
        android:layout_marginTop="20dp"
        android:layout_toEndOf="@id/btnStart"
        android:layout_marginStart="20dp"/>

    <Button
        android:id="@+id/btnReset"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Reset"
        android:layout_below="@id/txtTimer"
        android:layout_marginTop="20dp"
        android:layout_toEndOf="@id/btnStop"
        android:layout_marginStart="20dp"/>

</RelativeLayout>

The UI includes a `TextView` that displays the time in the center and three buttons (Start, Stop, Reset).
These buttons control the stopwatch’s functionality.

3. Implementing Stopwatch Functionality

Now that the UI is ready, it’s time to implement the watch functionality.
Open the `MainActivity.java` file and write the code as follows.

package com.example.stopwatchapp;

import android.os.Bundle;
import android.os.SystemClock;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    private TextView txtTimer;
    private Button btnStart, btnStop, btnReset;
    private long startTime = 0L;
    private boolean isRunning = false;
    private final Handler handler = new Handler();
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        txtTimer = findViewById(R.id.txtTimer);
        btnStart = findViewById(R.id.btnStart);
        btnStop = findViewById(R.id.btnStop);
        btnReset = findViewById(R.id.btnReset);
        
        btnStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!isRunning) {
                    startTime = SystemClock.elapsedRealtime();
                    handler.postDelayed(runnable, 0);
                    isRunning = true;
                }
            }
        });

        btnStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (isRunning) {
                    handler.removeCallbacks(runnable);
                    isRunning = false;
                }
            }
        });

        btnReset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                handler.removeCallbacks(runnable);
                txtTimer.setText("00:00:00");
                isRunning = false;
            }
        });
    }

    private final Runnable runnable = new Runnable() {
        @Override
        public void run() {
            long elapsedMillis = SystemClock.elapsedRealtime() - startTime;
            int seconds = (int) (elapsedMillis / 1000);
            int minutes = seconds / 60;
            seconds = seconds % 60;
            int hours = minutes / 60;
            minutes = minutes % 60;

            txtTimer.setText(String.format("%02d:%02d:%02d", hours, minutes, seconds));
            handler.postDelayed(this, 1000);
        }
    };
}

The above code contains the basic functionality of the stopwatch.
It uses a `Handler` to periodically update the elapsed time.

• Start Button: Starts the stopwatch and begins counting time.
• Stop Button: Stops the stopwatch and retains the current time.
• Reset Button: Resets the stopwatch and displays the time as “00:00:00”.

4. Testing the App

Now it’s time to test the stopwatch app. Click the “Run” button in Android Studio to
launch the app in the emulator. Click the buttons to verify that the stopwatch functionality works correctly.
It is important to test various scenarios to ensure all features operate seamlessly.

5. Implementing Additional Features

In addition to the basic stopwatch functionality, you might consider adding extra features to enhance the user experience.
For example, think about adding lap functionality, notification sounds, or user settings.

1. Lap Functionality:
   Add a feature that allows users to record elapsed times for multiple laps.
2. Sound Notifications:
   Provide feedback by sounding alerts when users start and stop the stopwatch.
3. Theme Settings:
   Offer users the option to change the colors or fonts of the app.

These features can improve the quality of the app and enhance user satisfaction.

6. Conclusion

In this tutorial, you learned how to develop an Android stopwatch app using Java. I hope that setting up the development environment,
designing the UI, and implementing functionality provided a foundation in Android app development.
I encourage you to add more features or continue to evolve your app in your own style.