Java GridBagLayout does not fill frame horizontally

Question

I am writing the GUI for a chat program. I can't seem to get the scroller to fill the frame horizontally and vertically and the messageInput to fill the frame horizontally. This is how it looks:

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

public class GUI extends JFrame{

private JPanel panel;
private JEditorPane content;
private JTextField messageInput;
private JScrollPane scroller;
private JMenu options;
private JMenuBar mb;
private JMenuItem item;

public GUI(){
    /** This is the frame**/
    this.setPreferredSize(new Dimension(380,600));
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    panel = new JPanel();
    panel.setLayout(new GridBagLayout());
    GridBagConstraints c = new GridBagConstraints();
    c.fill = GridBagConstraints.HORIZONTAL;

    /** This is where the context shows up **/
    content = new JEditorPane();
    content.setEditable(false);

    /** Scroller that shows up in the context JEditorPane **/
    scroller = new JScrollPane(content);
    c.weightx = 0.0;
    c.weighty = 0.0;
    c.gridx = 0;
    c.gridy = 0;
    panel.add(scroller, c);

    /** This is where you type your message **/
    messageInput = new JTextField();
    c.weightx = 0.0;
    c.weighty = 0.0;
    c.gridx = 0;
    c.gridy = 1;
    c.weighty = 0.5;
    panel.add(messageInput, c);

    mb = new JMenuBar();
    options = new JMenu("Options");
    mb.add(options);
    this.setJMenuBar(mb);

    this.add(panel);
    this.pack();
    this.setVisible(true);

}



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

Answer 1

get the scroller to fill the frame horizontally and vertically and the messageInput to fill the frame horizontally.

You want to fill in both directions, so set

c.fill = GridBagConstraints.BOTH; // not HORIZONTAL

The next part is to fix the weights, which will tell how much space to allocate for each component (relatively):

    scroller = new JScrollPane(content);
    c.weightx = 0.5;
    c.weighty = 1.0;
    c.gridx = 0;
    c.gridy = 0;
    panel.add(scroller, c);

    messageInput = new JTextField();
    c.weightx = 0.5;
    c.weighty = 0.0;
    c.gridx = 0;
    c.gridy = 1;
    panel.add(messageInput, c);

weightx should be a non-zero value to allow the components to stretch horizontally. weighty should be non-zero for the editor, but not for the text field so that it won't take extra vertical space (in this case you don't need to set c.fill = GridBagConstraints.HORIZONTAL for it).