如何在JPanel中画圆(java) 1D

Question

你好，我是JAVA的新手，最近学习了图形，但一直卡在如何画圆上（我通过Google自学）如果你能帮助我，我会很高兴以下代码行（不涉及后台子按钮）

public class Panel_ {
    static JPanel panel1 = new JPanel();

    public static Color randomColor() {
        int r = (int) Math.round(Math.random() * 255 - 1);
        int g = (int) Math.round(Math.random() * 255 - 1);
        int b = (int) Math.round(Math.random() * 255 - 1);
        Color R_col = new Color(r, g, b);
        System.out.println(R_col);
        return R_col;
    }

    public static void Panel() {

        var color_changer = new JButton("To change color");

        color_changer.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                panel1.setBackground(randomColor());
            }
        });

        var Panel = new JPanel();
        Panel.add(color_changer);
        Panel.setBackground(Color.blue);

        panel1.setBackground(Color.black);
        panel1.setPreferredSize(new Dimension(400, 430));

        var frame = new JFrame("Color changer");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(panel1, BorderLayout.NORTH);
        frame.getContentPane().add(Panel, BorderLayout.SOUTH);
        frame.pack();
        frame.setSize(500, 500);
        frame.setBackground(Color.blue);
        frame.setVisible(true);
    }

    public void paintCircle(Graphics g) {
        g.setColor(Color.blue);
        g.fillOval(60, 80, 100, 100);

    }

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

Answer 1

将 paintComponent 用于 panel1，我在下面的可运行代码中将名称更改为 topPanel：

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import javax.swing.*;

public class Panel extends JFrame {

    private static final long serialVersionUID = 1L;
    private JPanel topPanel;
    private JPanel panel;
    private JButton color_changer;
    
    
    public Panel() {
        initializeForm();
    }
    
    private void initializeForm() {
        setAlwaysOnTop(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBackground(Color.blue);
        
        color_changer = new JButton("To change color");
        color_changer.addActionListener((ActionEvent e) -> {
            topPanel.setBackground(randomColor());
        });

        topPanel = new JPanel() {
            private static final long serialVersionUID = 1L;
            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                g.setColor(Color.blue);
                g.fillOval(60, 80, 100, 100);
            };
        };
        
        panel = new JPanel();
        panel.add(color_changer);
        panel.setBackground(Color.blue);

        topPanel.setBackground(Color.black);
        topPanel.setOpaque(true);
        topPanel.setPreferredSize(new Dimension(400, 430));
        
        getContentPane().add(topPanel, BorderLayout.NORTH);
        getContentPane().add(panel, BorderLayout.SOUTH);
        pack();
        setLocationRelativeTo(null);
    }
    
    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(() -> {
            new Panel().setVisible(true);
        });
    }
    
    public static Color randomColor() {
        int r = (int) Math.round(Math.random() * 255 - 1);
        int g = (int) Math.round(Math.random() * 255 - 1);
        int b = (int) Math.round(Math.random() * 255 - 1);
        Color R_col = new Color(r, g, b);
        System.out.println(R_col);
        return R_col;
    }
    
}

如何在JPanel中画圆(java) 1D

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