JFrame底部的白边

问题描述

我正在使用 Javax swing，无法去掉 JFrame 底部的这个白色小边框。我的 JFrame 的结构方式是我将一堆组件添加到 JPanel（例如按钮、文本字段、标签），然后将其添加到框架中。我尝试将面板的首选大小设置为所需的尺寸，然后在 JFrame 上调用 pack() 但无济于事。提前致谢。

import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;

public class SampleGUI {
    JFrame frame;
    JPanel panel;
    JLabel label;
    JTextField field;

    public SampleGUI()
    {
        this.frame = new JFrame();
        this.panel = new JPanel();
        this.label = new JLabel("test");
        this.field = new JTextField(20);

        panel.setPreferredSize(new Dimension(500,250));
        panel.setLayout(null);

        label.setBounds(50,75,80,25);
        label.setForeground(Color.WHITE);
        panel.add(label);

        field.setBounds(120,20);
        panel.add(field);

        //Background Config
        try
        {
            URL url = new URL("https://watchandlearn.scholastic.com/content/dam/classroom-magazines/watchandlearn/videos/earth-and-space/earth-science-and-space/what-s-in-the-night-sky/english/wall-2018-whatsinthenightskymp4.transform/content-tile-large/image.png");
            BufferedImage image = ImageIO.read(url);
            JLabel img = new JLabel();
            img.setSize(500,250);
            img.setIcon(new ImageIcon(image));
            img.setopaque(false);
            panel.add(img);
        }
        catch(IOException ignored){}

        frame.setSize(500,250);
        frame.pack();
        frame.setLocationRelativeto(null);
        frame.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(panel);

        frame.setResizable(false);
        frame.setVisible(true);
    }
    public static void main(String[] args)
    {
        SampleGUI sample = new SampleGUI();
    }
}

解决方法

这是我放在一起的 GUI。我继续添加其他 Swing 组件。如您所见，底部没有线条。

我通过调用 SwingUtilities invokeLater 方法启动了 Swing 应用程序。此方法可确保在 Event Dispatch Thread 上创建和执行 Swing 组件。

我创建了一个绘图 JPanel，因此我可以在 JPanel 上绘制图像。我使 JPanel 成为图像的大小。我使用 GridBagLayout 来布置 JPanel 的组件。 GridBagLayout 会将 Swing 组件放在列中，并使组件组居中。

JFrame 方法调用必须按特定顺序调用。这是我用于 Swing 应用程序的顺序。

这是完整的可运行代码。我将附加类设为内部类，以便我可以将此代码作为一个块发布。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.image.BufferedImage;
import java.net.URL;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class StarryNightGUI implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new StarryNightGUI());
    }
    
    private BufferedImage image;
    
    private final BackgroundPanel backgroundPanel;
    
    public StarryNightGUI() {
        try {
            URL url = new URL("https://watchandlearn.scholastic.com/content/dam/"
                + "classroom-magazines/watchandlearn/videos/earth-and-space/"
                + "earth-science-and-space/what-s-in-the-night-sky/english/"
                + "wall-2018-whatsinthenightskymp4.transform/"
                + "content-tile-large/image.png");
            this.image = ImageIO.read(url);
        } catch (Exception e) {
            e.printStackTrace();
            this.image = null;
        }
        
         this.backgroundPanel = new BackgroundPanel();
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("Starry Night");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        
        frame.add(backgroundPanel,BorderLayout.CENTER);
        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }
    
    public class BackgroundPanel extends JPanel {
        
        private static final long serialVersionUID = 1L;

        public BackgroundPanel() {
            this.setPreferredSize(new Dimension(image.getWidth(),image.getHeight()));
            this.setLayout(new GridBagLayout());
            
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.anchor = GridBagConstraints.LINE_START;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            gbc.insets = new Insets(5,5,5);
            
            gbc.gridwidth = 2;
            gbc.gridx = 0;
            gbc.gridy = 0;
            String s = "Good Morning: " + LocalDateTime.now().format(
                    DateTimeFormatter.ofPattern("d MMM yyyy  H:mm a"));
            JLabel label = new JLabel(s);
            label.setForeground(Color.WHITE);
            add(label,gbc);
            
            gbc.gridwidth = 1;
            gbc.gridx = 0;
            gbc.gridy++;
            label = new JLabel("Username:");
            label.setForeground(Color.WHITE);
            add(label,gbc);
            
            gbc.gridx++;
            JTextField field = new JTextField(10);
            add(field,gbc);
            
            gbc.gridx = 0;
            gbc.gridy++;
            label = new JLabel("Password:");
            label.setForeground(Color.WHITE);
            add(label,gbc);
            
            gbc.gridx++;
            JPasswordField passwordField = new JPasswordField(10);
            add(passwordField,gbc);
            
            gbc.gridwidth = 2;
            gbc.gridx = 0;
            gbc.gridy++;
            
            JButton button = new JButton("Login");
            add(button,gbc);
        }
        
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawImage(image,this);
        }
        
    }

}

,

如果您只是想让代码正常工作，请将 frame.add(panel); 替换为 frame.setContentPane(panel); 并在框架包之前移动它

    frame.setContentPane(panel);
    frame.pack();

同时删除 frame.setSize(...)，因为 pack 方法会处理大小。

但是，总的来说，我建议您深入了解 Gilber 的回答，这样您就可以学到很多有关在面板中布置元素的知识。