1. Introduction
Android app development is a very important field in the current technology industry. Various apps are used on smartphones and tablets, making people’s daily lives more convenient. In this course, we will explore the characteristics of Android app development using Java, and conduct practical exercises through example code.
2. History of Android App Development
Android was developed by Android Inc. in 2003. After Google acquired Android Inc. in 2005, Android rapidly grew and became a widely used operating system across various platforms. It primarily operates on the Linux kernel, and apps are developed based on JAVA.
3. Setting Up the Android App Development Environment
To develop Android apps, you need to set up a development environment. The tools commonly used in this process are as follows:
- Java Development Kit (JDK): A development tool for creating programs in Java.
- Android Studio: Google’s official integrated development environment (IDE), which provides various tools and features necessary for creating Android apps.
- Android SDK (Software Development Kit): Includes libraries and APIs needed for Android development.
Once the development environment is set up, run Android Studio and create a new project. After completing the necessary configurations during this process, we will create our first app.
4. Features of Android Apps Using Java
Java is used as the primary programming language for Android, and many developers prefer it due to its stability and portability. Features of Android apps using Java include:
4.1. Object-Oriented Programming
Java is an object-oriented programming (OOP) language that structures code using classes and objects. This increases the reusability of the code and makes maintenance easier.
4.2. Portability
Applications developed in Java run on the JVM (Java Virtual Machine), so they possess portability that allows them to be used on various platforms.
4.3. Rich Libraries and APIs
Java provides various libraries and APIs that help developers implement functionalities more easily. The Android SDK includes UI components, networking, database functionalities, and more.
4.4. Concurrency
Android apps support asynchronous tasks. By using Java’s thread class, UI and backend tasks can be performed simultaneously.
5. Understanding the Structure of Android Apps
Android apps are generally composed of Activity, Service, Broadcast Receiver, and Content Provider.
5.1. Activity
An Activity creates the user interface and represents one screen of the app. Activities are important components for interacting with the user.
5.2. Service
A Service is a component that runs continuously in the background, used for tasks that require long execution time.
5.3. Broadcast Receiver
A Broadcast Receiver is a component that detects events occurring from the system or other apps.
5.4. Content Provider
A Content Provider provides a mechanism for sharing data between apps.
6. Basic Example: Creating Your First Android App
Now let’s create a simple Android app using Java. This app will have the functionality to take input from users and output it. Below are the steps.
6.1. Creating a Project in Android Studio
- Run Android Studio and create a new project.
- Select “Empty Activity” as the project template and enter the project name.
- Next, set the base package name and save path.
- Finally, click the Finish button to complete the project creation.
6.2. Creating the UI Layout
Now we will create the user interface through the XML file. Modify the res/layout/activity_main.xml file 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">
<EditText
android:id="@+id/editText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Enter your input" />
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/editText"
android:text="Submit" />
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/button"
android:text="Result" />
</RelativeLayout>
6.3. Writing Code for MainActivity.java
Now, let’s write the code in the MainActivity.java file to handle user input and display the result.
package com.example.myfirstapp;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
EditText editText = findViewById(R.id.editText);
Button button = findViewById(R.id.button);
TextView textView = findViewById(R.id.textView);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String input = editText.getText().toString();
textView.setText("Input value: " + input);
}
});
}
}
6.4. Running the App
After writing the code, run the app in Android Studio. You can test the app by connecting an emulator or a real Android device.
7. Publishing the Android App
Once app development is complete, it can be distributed on the Google Play Store. You just need to create an App Bundle or APK file for upload. During this process, you need to set the app’s icon, description, screenshots, etc.
8. Conclusion
Developing Android apps using Java is an attractive and challenging experience. I hope this course has helped you understand the basic development process and the characteristics of Android app development through practice. Based on this knowledge, I encourage you to move on to the next step and develop more diverse apps.