将JPanel添加到JPanel

Question

我正在尝试将JPanel添加到当前存在的JPanel中。当前存在的JPanel上面有大量的图像，我正在尝试加载另一个JPanel并将其放在我想要的坐标和我想要的大小的屏幕上。我该怎么做呢？这是我的代码：

当我将chatPanel添加到JFrame时，Demo类运行正常。但是，当我添加到我的面板时，它甚至都没有出现。

主要课程 -

        panel.add(Demo.chatPanel);
    frame.add(panel);

    new ResetEntities();
    frame.repaint();
    frame.setVisible(true);
    frame.setSize(1200, 800);

    //Demo.chatPanel.setLayout(null);
    panel.setLayout(null);

我要添加的面板......一个名为Demo的类

package level;

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.SwingConstants;

public class Demo {

public static JPanel chatPanel = new JPanel();

public Demo() {
    final JTextArea textArea = new JTextArea(5, 30);
    JScrollPane scrollPane = new JScrollPane(textArea);
    scrollPane.setPreferredSize(new Dimension(380, 100));
    textArea.setLineWrap(true);
    textArea.setWrapStyleWord(true);
    textArea.setEditable(false);
    scrollPane
            .setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
    final JTextField userInputField = new JTextField(30);
    userInputField.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent event) {
            String fromUser = userInputField.getText();
            if (fromUser != null) {
                textArea.append("Nic: " + fromUser + "\n");
                textArea.setCaretPosition(textArea.getDocument()
                        .getLength());
                userInputField.setText("");
            }
        }
    });
    chatPanel.add(userInputField, SwingConstants.CENTER);
    chatPanel.add(scrollPane, SwingConstants.CENTER);
}

}