我似乎無法讓這條線出現。我有背景顏色和幾張圖片。如果我有frame.setSize(x, y);，frame.setVisible(true); 那么結果與預期的一樣，但那里沒有這條線。如果我更改代碼并frame.從這兩行中洗掉，留下setSize(x,y);和setVisible(true);. 我嘗試過使用extends JPanel，extends JFrame但都沒有作業。我試過添加和洗掉@Override,paintComponent和g2d.drawLine.

無論是其中一個還是另一個，我如何讓兩者都作業？

import javax.swing.*;
import java.awt.*;
import javax.imageio.*;
import java.io.*;


public class CodeBreaker extends JPanel
{
    JFrame frame = new JFrame("Code Breaker!"); 
    Picture picture = new Picture("Empty.png"); 
    JLabel label = new JLabel(picture);
    JLabel label2 = new JLabel(picture);
    JLabel label3 = new JLabel(picture);
    JLabel label4 = new JLabel(picture);

    JLabel label5 = new JLabel(picture);
    JLabel label6 = new JLabel(picture);
    JLabel label7 = new JLabel(picture);
    JLabel label8 = new JLabel(picture);

    JPanel panel = new JPanel();
    JPanel panel2 = new JPanel();
    
    public CodeBreaker()
    {

        frame.setSize(600, 900); 
        frame.setContentPane(panel); 
        frame.add(panel2);
        frame.setResizable(true); 
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);   
        frame.getContentPane().setBackground(new Color(141, 100, 21));  

        panel.add(label);
        panel.add(label2);
        panel.add(label3);
        panel.add(label4);
    
        panel2.add(label5);
        panel2.add(label6);
        panel2.add(label7);
        panel2.add(label8);
        
        panel2.setOpaque(false);  
        
        frame.setVisible(true); 
    }

    /*
    void drawLines(Graphics g)
    {
        Graphics2D g2d = (Graphics2D) g;
 
        g2d.drawLine(120, 50, 360, 50);
 
    }
    */

    @Override
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g.setColor(Color.white);
        g.drawLine(120, 50, 360, 50);
    }
}

這是我的主要內容：

public class CodeBreakerDriver
{
    public static void main(String[] args)
    {
        CodeBreaker cb = new CodeBreaker();
    }
}

uj5u.com熱心網友回復：

介紹

Oracle 有一個有用的教程，

您可以在 GUI 的右下方看到一條黑線。

解釋

所有 Swing 應用程式都必須以呼叫該SwingUtilities invokeLater方法開始。此方法確保在Event Dispatch Thread上創建和執行 Swing 組件。

在單獨的方法中創建JFrameand 。JPanels這使得代碼更容易閱讀和理解。

使用Swing 布局管理器。有JFrame一個默認值BorderLayout。我FlowLayout對兩者都使用了 a JPanels。

代碼

這是完整的可運行代碼。我將該Picture類設為內部類，因此我可以將代碼作為一個塊發布。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.image.BufferedImage;

import javax.swing.BorderFactory;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class CodeBreakerGUI implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new CodeBreakerGUI());
    }
    
    private final Picture picture;
    
    public CodeBreakerGUI() {
        this.picture = new Picture();
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("Code Breaker!");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        frame.add(createTopPanel(), BorderLayout.NORTH);
        frame.add(createBottomPanel(), BorderLayout.SOUTH);
        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }
    
    public JPanel createTopPanel() {
        JPanel panel = new JPanel(new FlowLayout(FlowLayout.CENTER, 25, 25));
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        
        JLabel label = new JLabel(new ImageIcon(picture.getEmptyImage()));
        panel.add(label);
        
        JLabel label2 = new JLabel(new ImageIcon(picture.getEmptyImage()));
        panel.add(label2);
        
        JLabel label3 = new JLabel(new ImageIcon(picture.getEmptyImage()));
        panel.add(label3);
        
        JLabel label4 = new JLabel(new ImageIcon(picture.getEmptyImage()));
        panel.add(label4);
        
        return panel;
    }
    
    public JPanel createBottomPanel() {
        JPanel panel = new JPanel(new FlowLayout(FlowLayout.CENTER, 25, 25)) {
            private static final long serialVersionUID = 1L;

            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                g.setColor(Color.black);
                g.drawLine(120, 50, 360, 50);
            }
        };
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        
        JLabel label5 = new JLabel(new ImageIcon(picture.getEmptyImage()));
        panel.add(label5);
        
        JLabel label6 = new JLabel(new ImageIcon(picture.getEmptyImage()));
        panel.add(label6);
        
        JLabel label7 = new JLabel(new ImageIcon(picture.getEmptyImage()));
        panel.add(label7);
        
        JLabel label8 = new JLabel(new ImageIcon(picture.getEmptyImage()));
        panel.add(label8);
        
        return panel;
    }
    
    public class Picture {
        
        private final BufferedImage emptyImage;
        
        public Picture() {
            this.emptyImage = new BufferedImage(64, 64, BufferedImage.TYPE_INT_RGB);
        }

        public BufferedImage getEmptyImage() {
            return emptyImage;
        }
        
    }

}

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