Swing Component Not Centering

Question

我剛剛在我的GUI中添加了徽標和測試版消息。然而，它正確地完全不是那麼回事中心：

這裏是我的代碼：

package me.nrubin29.quiz.create; 

import me.nrubin29.quiz.MessageUtil; 

import javax.swing.*; 
import java.awt.*; 
import java.awt.event.*; 
import java.io.File; 

public class WelcomeGUI extends JFrame { 

    private static final long serialVersionUID = 1L; 

    private DefaultListModel contents = new DefaultListModel(); 
    private JLabel logo, betaText = new JLabel("This is beta software and should not be distributed without consent from its creator."); 
    private JList list = new JList(contents); 
    private JPanel contentsPanel = new JPanel(), buttonPanel = new JPanel(), logoPanel = new JPanel(), betaPanel = new JPanel(); 
    private JButton open = new JButton("Open"), delete = new JButton("Delete"), rename = new JButton("Rename"), newQuiz = new JButton("New"); 

    public WelcomeGUI() { 
     super("AutoQuiz"); 

     try { logo = new JLabel(MessageUtil.ImageType.LOGO_LANDSCAPE.getImageIcon()); } 
     catch (Exception e) { e.printStackTrace(); } 

     logo.setHorizontalAlignment(SwingConstants.CENTER); 

     betaText.setHorizontalAlignment(SwingConstants.CENTER); 

     list.addMouseListener(new MouseAdapter() { 
      @Override 
      public void mouseClicked(MouseEvent evt) { 
       if (evt.getClickCount() == 2) open.doClick(); 
      } 
     }); 

     list.addKeyListener(new KeyAdapter() { 
      @Override 
      public void keyPressed(KeyEvent e) { 
       if (e.getKeyCode() == KeyEvent.VK_ENTER) open.doClick(); 
      } 
     }); 

     for (String file : FileManager.getInstance().getRootFolder().list()) { 
      try { if (file.substring(file.lastIndexOf(".")).equals(".quiz")) contents.addElement(file.substring(0, file.lastIndexOf("."))); } 
      catch (Exception ignored) { } 
     } 

     if (contents.size() > 0) list.setSelectedIndex(0); 

     open.addActionListener(new ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
       if (list.getSelectedIndex() != -1) { 
        File load = FileManager.getInstance().getFile(contents.get(list.getSelectedIndex()) + ".quiz"); 
        new CreatorGUI(load, WelcomeGUI.this); 
       } 
      } 
     }); 

     delete.addActionListener(new ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
       if (list.getSelectedIndex() != -1) { 
        File choice = FileManager.getInstance().getFile(contents.get(list.getSelectedIndex()) + ".quiz"); 
        contents.remove(list.getSelectedIndex()); 
        if (!choice.delete()) MessageUtil.msg(WelcomeGUI.this, "Error", "Could not delete file.", MessageUtil.MessageType.ERROR, MessageUtil.ImageType.ICON); 
       } 
      } 
     }); 

     rename.addActionListener(new ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
       if (list.getSelectedIndex() != -1) { 
        File load = FileManager.getInstance().getFile(contents.get(list.getSelectedIndex()) + ".quiz"); 
        String name = JOptionPane.showInputDialog(WelcomeGUI.this, "Please enter a new name.", contents.get(list.getSelectedIndex())); 
        if (name == null) return; 
        if (!load.renameTo(FileManager.getInstance().getFile(name + ".quiz"))) MessageUtil.msg(WelcomeGUI.this, "Error", "Could not rename file.", MessageUtil.MessageType.ERROR, MessageUtil.ImageType.ICON); 
        else contents.setElementAt(name, list.getSelectedIndex()); 
       } 
      } 
     }); 

     newQuiz.addActionListener(new ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
       String name = JOptionPane.showInputDialog(WelcomeGUI.this, "Please enter a name for the quiz."); 
       if (name == null) return; 
       else name += ".quiz"; 
       new CreatorGUI(FileManager.getInstance().getFile(name), WelcomeGUI.this); 
       WelcomeGUI.this.dispose(); 
      } 
     }); 

     JScrollPane listPane = new JScrollPane(list); 
     listPane.setPreferredSize(new Dimension(500, 125)); 

     getContentPane().setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS)); 
     buttonPanel.setLayout(new BoxLayout(buttonPanel, BoxLayout.Y_AXIS)); 
     logoPanel.setLayout(new BoxLayout(logoPanel, BoxLayout.Y_AXIS)); 

     logoPanel.add(logo); 
     buttonPanel.add(open); buttonPanel.add(delete); buttonPanel.add(rename); buttonPanel.add(newQuiz); 
     contentsPanel.add(listPane); contentsPanel.add(buttonPanel); 
     betaPanel.add(betaText); 
     add(logoPanel); add(contentsPanel); add(betaPanel); 

     Dimension DIM = new Dimension(640, 250); 
     setPreferredSize(DIM); 
     setSize(DIM); 
     setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); 
     setLocationRelativeTo(null); 
     setResizable(false); 
     pack(); 
     setVisible(true); 
    } 

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

Answer 1

你可以使用

logo.setAlignmentX(Component.CENTER_ALIGNMENT);