Expanding a node of a JTree minimizes GridBagLayout

Question

I have created a simple Swing application which currently consists of a JToolBar, a JTree and a RSyntaxTextArea, all inside a GridBagLayout.

The JTree has currently only one top node and that has only one child node. Complete UI with JToolBar, JTree and RSyntaxTextArea

When expanding the top node of the JTree, the whole GridBagLayout kind of "minimizes":

I've googled this phenominum, but since there's no error message or something else in the console, I'm kind of helpless right now.

I'm using the following code to create the UI:

RSyntaxTextArea textArea = new RSyntaxTextArea(50, 150);
textArea.setSyntaxEditingStyle(SyntaxConstants.SYNTAX_STYLE_JAVA);
textArea.setCodeFoldingEnabled(true);
RTextScrollPane sp = new RTextScrollPane(textArea);

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

c.gridx = 0;
c.gridy = 0;
cp.add(createToolbar(), c);

c.gridx = 0;
c.gridy = 1;
c.ipadx = 90;
c.fill = GridBagConstraints.BOTH;
cp.add(createTree(), c);

c.gridx = 1;
c.gridy = 1;
c.fill = GridBagConstraints.HORIZONTAL;
cp.add(sp, c);

...

private JToolBar createToolbar() {
    JToolBar tb = new JToolBar("Toolbar", JToolBar.HORIZONTAL);

    JButton ob = new JButton(new ImageIcon("..."));

    tb.add(ob);

    tb.setFloatable(false);
    tb.setRollover(true);

    return tb;
}

...

private JTree createTree() {
    DefaultMutableTreeNode top = new DefaultMutableTreeNode("Projects");
    JTree tree = new JTree(top);

    DefaultMutableTreeNode test = new DefaultMutableTreeNode("I'm a test!");
    top.add(test);

    return tree;
}

Update: A minimal code example to compile on your system for testing purposes:

import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JToolBar;
import javax.swing.JTree;
import javax.swing.SwingUtilities;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class Tester extends JFrame {

    public Tester () {
        initializeComponent();
    }

    private void initializeComponent() {
        JPanel cp = new JPanel(new BorderLayout());
        JTextArea textArea = new JTextArea(50, 150);
        JScrollPane sp = new JScrollPane(textArea);
        cp.setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        c.fill = GridBagConstraints.HORIZONTAL;
        c.gridx = 0;
        c.gridy = 0;
        cp.add(createToolbar(), c);
        c.gridx = 0;
        c.gridy = 1;
        c.ipadx = 90;
        c.fill = GridBagConstraints.BOTH;
        cp.add(createTree(), c);
        c.gridx = 1;
        c.gridy = 1;
        c.fill = GridBagConstraints.HORIZONTAL;
        cp.add(sp, c);
        setContentPane(cp);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();
        setLocationRelativeTo(null);
    }

    private JTree createTree() {
        DefaultMutableTreeNode top = new DefaultMutableTreeNode("Projects");
        JTree tree = new JTree(top);
        DefaultMutableTreeNode test = new DefaultMutableTreeNode("I'm a test!");
        top.add(test);
        return tree;
    }

    private JToolBar createToolbar() {
        JToolBar tb = new JToolBar("Toolbar", JToolBar.HORIZONTAL);
        JButton ob = new JButton("Button");
        tb.add(ob);
        tb.setFloatable(false);
        tb.setRollover(true);
        return tb;
    }

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

}

Please consider creating and posting in your question a valid [mcve] a ***small*** program that we can compile, run, and that demonstrates your problem for us. — Hovercraft Full Of Eels, Jul 25 '17 at 17:01
(1-) @AlexanderLeithner, The code you posted is NOT an `MCVE` since we don't have access to the custom classes. In any case you already have your answer. Time to do some reading. — camickr, Jul 25 '17 at 17:34
@camickr Oh, thank you, overlooked them... Will replace them by simple JTextAreas right now... — Alexander Leithner, Jul 25 '17 at 17:41

camickr · Accepted Answer · 2017-07-25T17:30:36.547

2

When expanding the top node of the JTree, the whole GridBagLayout kind of "minimizes":

The GridBagLayout will shrink to the minimum size of a component when there is not enough space to display the entire component.

Swing application which currently consists of a JToolBar, a JTree and a RSyntaxTextArea, all inside a GridBagLayout.

I would just use the default BorderLayout of the frame:

add(toolbar, BorderLayout.PAGE_START);
add(treeScrollPane, BorderLayout.CENTER);
add(textAreaScrollPane, BorderLayout.PAGE_END);

Note how I added the JTree to a JScrollPane. Now scrollbars will appear for the tree when needed.

If you really want to use the GridBagLayout then read the section from the Swing tutorial on How to Use GridBagLayout for an explanation of how to use the various constraints. You may want to start with the "weightx/y" constraints which control which components get space as the frame size is changed. Also, look at the "fill" constraint.

edited Jul 25 '17 at 17:30

answered Jul 25 '17 at 17:24

camickr

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That would append the RSyntaxTextArea to the end of the dialog, right? That's not how I want it to be displayed, just next to the JTree on its right. But good to know about the shrinking (but I really do not know why there should not be enough space)... – Alexander Leithner Jul 25 '17 at 17:29
@AlexanderLeithner, `I want it to be displayed, just next to the JTree on its right` - so then use a different BorderLayout constraint to put the text area on the right. Read the tutorial. I provided a link to the GridBagLayout. You will also find a section on the BorderLayout. – camickr Jul 25 '17 at 17:31
Thank you, overlooked `weightx/y` (but had read this tutorial before)... – Alexander Leithner Jul 25 '17 at 17:51

Expanding a node of a JTree minimizes GridBagLayout

1 Answers1