How to develop a simple GUI application using Java

How to use Java to develop a simple GUI application

With the advancement of computer technology, Graphical User Interface (GUI) has become a mainstream application Program Standards. As a powerful programming language, Java provides a wealth of GUI development tools and frameworks, allowing developers to easily create powerful and easy-to-use graphical interface applications.

This article will take a simple calculator application as an example to introduce how to use the Java Swing library to develop a simple GUI application.

1. Create a Java project

First, we need to create a Java project and create a new Java class in the project. Suppose our project is called SimpleCalculator, we can create a Java class called Calculator.

2. Import the required libraries

At the top of the Java class we need to import the required libraries:

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

3. Create the GUI component

In Java classes, we can define various GUI components such as buttons, text boxes, and labels. We can use the JFrame class to create an application window, the JButton class to create buttons, the JLabel class to create labels, the JTextField class to create text boxes, etc.

public class Calculator extends JFrame {
    private JTextField textField;
    private JButton button1;
    private JButton button2;
    // ...
    private JButton button9;
    private JButton buttonAdd;
    private JButton buttonSubtract;
    // ...
    private JButton buttonEquals;

    public Calculator() {
        super("Simple Calculator");
 
        // 设置窗口的大小和布局
        setSize(300, 400);
        setLayout(new BorderLayout());
 
        // 创建文本框和标签
        textField = new JTextField();
        JLabel label = new JLabel("Calculator");
 
        // 创建按钮
        button1 = new JButton("1");
        button2 = new JButton("2");
        // ...
        button9 = new JButton("9");
        buttonAdd = new JButton("+");
        buttonSubtract = new JButton("-");
        // ...
        buttonEquals = new JButton("=");
 
        // 添加组件到窗口中
        add(label, BorderLayout.NORTH);
        add(textField, BorderLayout.CENTER);
        add(button1);
        add(button2);
        // ...
        add(button9);
        add(buttonAdd);
        add(buttonSubtract);
        // ...
        add(buttonEquals, BorderLayout.SOUTH);
 
        // 设置按钮的监听器
        button1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                textField.setText(textField.getText() + "1");
            }
        });
        button2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                textField.setText(textField.getText() + "2");
            }
        });
        // ...
        button9.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                textField.setText(textField.getText() + "9");
            }
        });
        buttonAdd.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                textField.setText(textField.getText() + "+");
            }
        });
        buttonSubtract.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                textField.setText(textField.getText() + "-");
            }
        });
        // ...
        buttonEquals.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String expression = textField.getText();
                // 进行计算并在文本框中显示结果
                textField.setText(calculate(expression));
            }
        });
 
        // 设置窗口可见
        setVisible(true);
    }

    // 实现计算逻辑
    private String calculate(String expression) {
        // TODO: 实现计算逻辑
        return "";
    }
 
    public static void main(String[] args) {
        new Calculator();
    }
}

4. Implementing calculation logic

In the above code, we use a calculate method to implement the actual calculation logic. In this method, we can parse the expression and perform the corresponding calculation operation, and then return the result.

5. Run the program

Finally, we can test our simple calculator application by running the program. In the main method, we create a Calculator object that will create a window and display the GUI components we defined.

public static void main(String[] args) {
    new Calculator();
}

Summary:

By using the Java Swing library, we can easily create a simple GUI application. This article takes a simple calculator application as an example to introduce in detail how to create GUI components, set layout, add event listeners, and implement calculation logic. I hope this article can help you get started developing GUI applications in Java and inspire you to further learn and explore other GUI development tools and frameworks.

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