我的JPanel中的GridBagLayout无法正常工作

您对gridHeight和gridWidth常量的使用似乎已关闭，并且似乎期望使用GridBagLayout没有的功能。例如，您不必通过这种方式定义JTextArea的列大小和行大小。而是通过调用适当的构造函数或方法来设置文本组件的行大小和列大小以及JList的原型大小。例如：

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

public class InGameMenu extends JPanel {

   private static final String[] EXAMPLE_TEXT = {"One", "Two", "Three"};
   private static final int COLUMNS = 40;
   private static final int ROWS = 20;
   private JTextArea chatBox;
   private JPanel buttonPanel;
   private TextField chatTextField;
   private JList playersList;
   private DefaultListModel listModel;
   // private ConnectionToServer conn;
   private JFrame mainFrame;

   // public InGameMenu (ConnectionToServer conn, JFrame mainFrame)
   public InGameMenu(JFrame mainFrame) {

      this.setBackground(Color.CYAN);
      // this.conn = conn;
      this.mainFrame = mainFrame;
      mainFrame.setTitle("Game menu");
      super.setLayout(new GridBagLayout());
      // chatBox = new JTextArea("This is player's chat.\n");
      chatBox = new JTextArea("This is player's chat.\n", ROWS, COLUMNS);

      GridBagConstraints gbc = new GridBagConstraints();

      // chat box
      // gbc.gridheight = 10;
      // gbc.gridwidth = 10;
      gbc.fill = GridBagConstraints.BOTH;
      gbc.gridx = 0;
      gbc.gridy = 0;
      // this.add(chatBox, gbc);
      chatBox.setWrapStyleWord(true);
      chatBox.setLineWrap(true);
      JScrollPane scrollPane = new JScrollPane(chatBox);
      this.add(scrollPane, gbc);


      // chat text field
      chatTextField = new TextField("dsadasda", COLUMNS);
      chatTextField.setBackground(Color.GRAY);
      // gbc.gridheight = 1;
      gbc.gridy = 1;
      this.add(chatTextField, gbc);

      // lista graczy
      listModel = new DefaultListModel();
      for (int i = 0; i < EXAMPLE_TEXT.length; i++) {
         listModel.addElement(EXAMPLE_TEXT[i]);
      }
      playersList = new JList(listModel);
      playersList.setPrototypeCellValue(String.format("%40s", " "));

      // gbc.gridheight = 15;
      // gbc.gridwidth = 4;
      gbc.gridx = 1;
      gbc.gridy = 0;
      this.add(playersList, gbc);

      // panel przyciskow
      buttonPanel = new JPanel(new FlowLayout());
      // gbc.gridheight = 1;
      gbc.gridy = 1;
      this.add(buttonPanel, gbc);

   }

   public InGameMenu() {
      // TODO Auto-generated constructor stub
   }

   private static void createAndShowGui() {

      JFrame frame = new JFrame("In Game Menu");
      InGameMenu mainPanel = new InGameMenu(frame);
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

现在，如果要让组件填充视图，则需要将weightx和权重GridBagConstraints设置为非零值。