Question

The following problem boggled my mind, so I came here for some help.

After experimenting I ended up with this block of code:

JTextArea chatPanel = null;
JScrollPane scrollPanel = null;

if(chatPanel == null)
{
    chatPanel = new JTextArea("derp");
    chatPanel.setEditable(false);
    chatPanel.setForeground(new Color(10,191,26));
    chatPanel.setOpaque(false);
    scrollPanel = new JScrollPane(chatPanel);
    scrollPanel.setOpaque(false);
    scrollPanel.getViewport().setOpaque(false);
    scrollPanel.setBorder(BorderFactory.createEmptyBorder());
}

//## marked area ##         
scrollPanel.setBounds(9,596,435,138);
pane.add(scrollPanel);              

The result? Nothing shows up. The text area with “derp” in it I expected is not there, just an empty scroll panel. Now, if I go to the ## marked area ## and replace it with this:

chatPanel.append("Hello.");

the chatPanel shows up fine in the scrollPanel, with its text being “derpHello.”. Any ideas as per what’s going on?

For the record, pane is a simple container with a null layout that otherwise displays eveyrthing fine. Declaration, just for the record:

Container pane = getContentPane()
pane.setLayout(null);

Answer 1

I have no problem with the following code, I can see the “derp” in green just fine:

import java.awt.Color;
import java.awt.Container;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class TestTextArea {

    private void initUI() {
        JFrame frame = new JFrame("test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JTextArea chatPanel = null;
        JScrollPane scrollPanel = null;
        Container pane = frame.getContentPane();
        pane.setLayout(null);
        if (chatPanel == null) {
            chatPanel = new JTextArea("derp");
            chatPanel.setEditable(false);
            chatPanel.setForeground(new Color(10, 191, 26));
            chatPanel.setOpaque(false);
            scrollPanel = new JScrollPane(chatPanel);
            scrollPanel.setOpaque(false);
            scrollPanel.getViewport().setOpaque(false);
            scrollPanel.setBorder(BorderFactory.createEmptyBorder());
        }

        // ## marked area ##
        scrollPanel.setBounds(9, 596, 435, 138);
        pane.add(scrollPanel);
        frame.validate();
        frame.setSize(600, 800);
        frame.setVisible(true);
    }

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

            @Override
            public void run() {
                new TestTextArea().initUI();
            }
        });
    }

}

Now, I would really advise you to use an appropriate LayoutManager instead of that null layout. That would allow you to use pack() and revalidate() and have a much simpler and more maintainable code.

There must be something else that your code does not illustrate for now. Try to put an SSCCE.