Java Android App Development Course, Running the App

Android app development is one of the popular fields for many developers today. In particular, Java is one of the most widely used programming languages for Android app development. In this course, we will explain in detail how to develop and run Android apps using Java. This course will comprehensively cover everything from setting up the Android development environment to creating and running a simple example app.

1. Setting Up the Android Development Environment

To start Android app development, you must first set up the development environment. Officially, install Android Studio, which is provided by Google. Android Studio is an integrated development environment (IDE) for developing Android apps that offers various features to help make development easier.

1.1 Installing Android Studio

Visit the Android Studio website (developer.android.com/studio) and download the installation file.
Run the downloaded file and follow the installation wizard to proceed with the installation.
Once installation is complete, run Android Studio.

1.2 Installing JDK

To develop Android apps, you need the Java Development Kit (JDK). If the JDK is not already installed, you must download and install it from Oracle’s official website.

2. Creating a New Project

Once the development environment is set up, let’s create a new Android project. Please follow the steps below.

Run Android Studio and click ‘New Project’.
Select ‘Empty Activity’ and click the ‘Next’ button.
Choose the project name, package name, project location, and language (Java), then click the ‘Finish’ button.

3. Understanding the App Structure

An Android app consists of multiple files and folders. The main components are as follows:

AndroidManifest.xml: A file that defines the app’s metadata. It allows you to configure the app’s components, permissions, API levels, etc.
res/: A folder that stores resource files (images, layouts, strings, etc.) used by the app.
java/: A folder where Java source files are stored, which is where you implement the main logic of the app.

4. Developing a Simple App

Here, we will create a simple app that displays the message “Hello, Android!” when the button is clicked.

4.1 Setting Up the Layout

First, modify the activity_main.xml file to add a button and a text view. This file is located in the res/layout/ folder. Please enter the following code:

<?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/text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello!"
        android:layout_centerInParent="true"
        android:textSize="24sp" />

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

</RelativeLayout>

4.2 Writing the Java Code

Next, modify the main activity file (MainActivity.java) to handle the button click event. It is located in the java/com.example.yourapp/ folder. Please modify it with the following code:

package com.example.yourapp;

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

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

5. Running the App

Now it’s time to run the app. Please follow the steps below.

Click the “Run” button on the Android Studio toolbar.
Select a virtual device or physical device. If you want to use a virtual device, you need to set up an Android Virtual Device (AVD). If AVD is not installed by default, you can set it up through the AVD Manager.
Once the app is built, it will run on the selected device.

5.1 Setting Up AVD

To set up a virtual device, follow these steps:

Click the “AVD Manager” icon in Android Studio.
Click “Create Virtual Device” and choose the desired device.
Select the system image to use for the selected device.
Click “Finish” to create the virtual device.

6. App Execution Result

If the app runs successfully, clicking the button will display the message “Hello, Android!” in the TextView. This simple app helps you understand the basic flow of Android development.

7. Conclusion

In this course, we covered the start of Android app development using Java. We explained the installation of Android Studio, creating a new project, understanding app structure, developing and running a simple app in a total of 7 steps. Through this process, developers can easily create and run basic apps, and later move on to more complex app development.

Now you have the fundamentals to develop your own apps using Java and Android Studio. In the future, explore various features related to Java and Android development through more extensive exploration.

8. Next Steps: Getting Familiar

To take a step further, it is essential to use various resources to enhance your app. It would be beneficial to explore the following topics:

Android UI Components: ListView, RecyclerView, Toolbar, etc.
Data Storage: SQLite, Shared Preferences
Networking: Retrofit, Volley
Multimedia: Camera, audio recording functionality, etc.

All these processes will be important guides to help you grow into a better Android developer.