Drawline 不适用于 JPanel 或 JFrame

Question

我似乎无法显示该行。我有背景颜色和一些图片。如果我有 frame.setSize(x, y); 和 frame.setVisible(true); 那么结果就如预期的那样，但那里没有线。如果我更改代码并从这两行中删除 frame.，留下 setSize(x,y); 和 setVisible(true);。我试过使用 extends JPanel 和 extends JFrame 但都不起作用。我尝试添加和删除 @Override、paintComponent 和 g2d.drawLine.

两者都可以，我如何才能使两者都起作用？

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);
    }
}

这是我的主要内容：

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

Answer 1

简介

Oracle 有一个有用的教程，Creating a GUI With Swing。跳过使用 NetBeans 学习 Swing IDE 部分。

由于您 post 编写的代码不可执行，我继续创建了以下 GUI。

您可以在 GUI 的右下方看到一条黑线。

说明

所有 Swing 应用程序必须以调用 SwingUtilities invokeLater 方法开始。此方法确保 Swing 组件在 Event Dispatch Thread.

上创建和执行

在不同的方法中创建 JFrame 和 JPanels。这使代码更易于阅读和理解。

使用Swing layout managers。 JFrame 有一个默认值 BorderLayout。我对 JPanels.

都使用了 FlowLayout

代码

这是完整的可运行代码。我将 Picture class 设为内部 class 这样我就可以 post 将代码作为一个块。

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;
        }
        
    }

}

Drawline 不适用于 JPanel 或 JFrame

Drawline not working with JPanel or JFrame

java

swing

jframe

简介

说明

代码