JPanel in GridBagLayout does not keep proportion (weightx)

Question

I have the following situation. I've created a JPanel with GridBagLayout with the following proportions. I want to get this straight, and after that I will add more components. For now I have something like

------------------------------------
|LABEL 45%  | LABEL 10% | LABEL 45%|
------------------------------------

Each label takes 1 cell horizontally and vertically (gridwidth/height = 1)

Weights (x) are 0.45, 0.1 and 0.45 (from left to right)

Weights (y) are 0.0

All labels have fill GBC.HORIZONTAL and the anchors are WEST, WEST, EAST.

JPanel topPanel = new JPanel(new GridBagLayout());

    topPanel.add(new JLabel("1"), new GridBagConstraints(
        0, 0, 1, 1, 0.45, 0.0, GridBagConstraints.WEST,
        GridBagConstraints.HORIZONTAL, INSETS_0PX, 0, 0));
    topPanel.add(new JLabel("2"), new GridBagConstraints(
        1, 0, 1, 1, 0.1, 0.0, GridBagConstraints.WEST,
        GridBagConstraints.BOTH, INSETS_0PX, 0, 0));
    topPanel.add(new JLabel("3"), new GridBagConstraints(
        2, 0, 1, 1, 0.45, 0.0, GridBagConstraints.EAST,
        GridBagConstraints.HORIZONTAL, INSETS_0PX, 0, 0));

At this point everything is OK, the first label gets the exact same space as the right label (which is 45% of the width available, and the other one gets 10%). Perfect.

But when I try to add, instead of a label (either left/right), another JPanel with a GridBagLayout, the proportions are not kept as defined.

In the left I want to add a JPanel which is defined as follows

----------------------
|JLabel..............|
|--------------------|
|JTextArea...........|
|....................|
----------------------

JLabel has weights 0.0 (for both x/y), WEST anchor, and fill NONE

JTextArea - weights 1.0(x), 1.0, WEST anchor, fill BOTH (in order to stretch)

myPanel = new JPanel(new GridBagLayout());
myPanel.add(new JLabel("TITLE", new GridBagConstraints(0, 0, 1, 1, 0.0, 0.0,
        GridBagConstraints.WEST, GridBagConstraints.NONE, INSETS_0PX, 0, 0));
myPanel.add(new JTextArea(5,25), new GridBagConstraints(0, 1, 1, 1, 1.0, 1.0,
        GridBagConstraints.WEST, GridBagConstraints.BOTH, INSETS_0PX, 0, 0));

In the right, I want to add a JPanel with a GridBagLayout which holds two other JPanels with GridBagLaouts (there's no point in describing now how is defined).

--> therefore, at the moment when I add the left panel instead of the label, it gets somewhere around 60% of the screen (which is not right, it should get 45%).

Can you spot what is wrong? I'm out of ideas

LE: here's the simple example

public class Example extends JFrame {

public Example() {
    init();
}

private JPanel createPanel(Component comp) {
    JPanel topPanel = new JPanel(new GridBagLayout());

    topPanel.add(comp, new GridBagConstraints(
        0, 0, 1, 1, 0.45, 0.0, GridBagConstraints.WEST,
        GridBagConstraints.HORIZONTAL, new Insets(0,0,0,0), 0, 0));
    topPanel.add(new JLabel("2"), new GridBagConstraints(
        1, 0, 1, 1, 0.1, 0.0, GridBagConstraints.WEST,
        GridBagConstraints.BOTH, new Insets(0,0,0,0), 0, 0));
    topPanel.add(new JLabel("3"), new GridBagConstraints(
        2, 0, 1, 1, 0.45, 0.0, GridBagConstraints.EAST,
        GridBagConstraints.HORIZONTAL, new Insets(0,0,0,0), 0, 0));

    return topPanel;
}

private JPanel getPanelWithLabel() {
    return createPanel(new JLabel("1"));
}

private JPanel getPanelWithPanel() {
    JPanel myPanel = new JPanel(new GridBagLayout());
    myPanel.add(new JLabel("TITLE"), new GridBagConstraints(0, 0, 1, 1, 0.0, 0.0,
            GridBagConstraints.WEST, GridBagConstraints.NONE, new Insets(0,0,0,0), 0, 0));
    myPanel.add(new JTextArea(5,25), new GridBagConstraints(0, 1, 1, 1, 1.0, 1.0,
            GridBagConstraints.WEST, GridBagConstraints.BOTH, new Insets(0,0,0,0), 0, 0));
    return createPanel(myPanel);
}

private void init() {
    setTitle("Simple example");
    setSize(800, 200);
    setLocationRelativeTo(null);
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    JPanel panel = new JPanel(new BorderLayout());
    panel.add(getPanelWithLabel(), BorderLayout.CENTER);
//panel.add(getPanelWithPanel(), BorderLayout.CENTER);

    add(panel);
    setVisible(true);
}

public static void main(String[] args) {

    EventQueue.invokeLater(new Runnable() {

        @Override
        public void run() {
            Example ex = new Example();
        }
    });

}
}

For better help sooner, post a minimal reproducible example or Short, Self Contained, Correct Example. — Andrew Thompson
If you add the JPanel alone with the JLabel without the JTextArea? To know if the problem is the JPanel or the JTextArea... — Yassin Hajaj
@YassinHajaj I've removed the myPanel.add(new JTA()..), but still the same result. The left part gets 445px, right one 400px — Marius Manastireanu

Yassin Hajaj Yassin Hajaj · Accepted Answer · 2015-11-19T13:37:20

The problem lays with the rows of your JTextArea.

As 25 rows is wider than the 45%, it expends itself.

Instead of using 25, I'd use the WIDTH of the container (myPanel)

Solution

myPanel.add(new JTextArea(5,myPanel.WIDTH), new GridBagConstraints(0, 1, 1, 1, 1.0, 1.0,
                GridBagConstraints.WEST, GridBagConstraints.BOTH, INSETS_0PX, 0, 0));

Output

EDIT

Since the sizes are still different with this method. I tried to create first a JPanel and to add the JLabel to it.

Solution

JPanel threeCont = new JPanel(new GridBagLayout());
threeCont.add(new JLabel("3"), new GridBagConstraints(0, 0, 1, 1, 0.0, 0.0,
        GridBagConstraints.WEST, GridBagConstraints.NONE, INSETS_0PX, 0, 0));
// We add myPanel and two(JLabel) to topPanel first and than the below.
topPanel.add(threeCont, new GridBagConstraints(
    2, 0, 1, 1, 0.45, 0.0, GridBagConstraints.EAST,
    GridBagConstraints.HORIZONTAL, INSETS_0PX, 0, 0));

Output

System.out.println("First Panel's Size : " + myPanel.getSize());
System.out.println("Second Panel's Size : " +two.getSize());
System.out.println("Third Panel's Size : " +threeCont.getSize());

Console

First Panel's Size : java.awt.Dimension[width=441,height=96]
Second Panel's Size : java.awt.Dimension[width=98,height=96]
Third Panel's Size : java.awt.Dimension[width=441,height=16]

Full code

public static void main(String[]a) {
    JFrame fr = new JFrame();
    fr.setSize(new Dimension(1000,1000));
    fr.setLocationRelativeTo(null);
    JPanel topPanel = new JPanel(new GridBagLayout());
    Insets INSETS_0PX = new Insets(0,0,0,0);
    JLabel one = new JLabel("1");
    JLabel two = new JLabel("2");
    one.setBackground(Color.yellow);
    two.setBackground(Color.blue);

    JPanel myPanel = new JPanel(new GridBagLayout());
    myPanel.add(new JLabel("TITLE"), new GridBagConstraints(0, 0, 1, 1, 0.0, 0.0,
            GridBagConstraints.WEST, GridBagConstraints.NONE, INSETS_0PX, 0, 0));
    myPanel.add(new JTextArea(5,myPanel.WIDTH), new GridBagConstraints(0, 1, 1, 1, 1.0, 1.0,
            GridBagConstraints.WEST, GridBagConstraints.BOTH, INSETS_0PX, 0, 0));

    JPanel threeCont = new JPanel(new GridBagLayout());
    threeCont.add(new JLabel("TITLE"), new GridBagConstraints(0, 0, 1, 1, 0.0, 0.0,
            GridBagConstraints.WEST, GridBagConstraints.NONE, INSETS_0PX, 0, 0));

    topPanel.add(myPanel, new GridBagConstraints(
        0, 0, 1, 1, 0.45, 0.0, GridBagConstraints.WEST,
        GridBagConstraints.HORIZONTAL, INSETS_0PX, 0, 0));

    topPanel.add(two, new GridBagConstraints(
        1, 0, 1, 1, 0.1, 0.0, GridBagConstraints.WEST,
        GridBagConstraints.BOTH, INSETS_0PX, 0, 0));

    topPanel.add(threeCont, new GridBagConstraints(
        2, 0, 1, 1, 0.45, 0.0, GridBagConstraints.EAST,
        GridBagConstraints.HORIZONTAL, INSETS_0PX, 0, 0));


    fr.add(topPanel);

    fr.setVisible(true);

    System.out.println("First Panel's Size : " + myPanel.getSize());
    System.out.println("Second Panel's Size : " +two.getSize());
    System.out.println("Third Panel's Size : " +threeCont.getSize());
}

JPanel in GridBagLayout does not keep proportion (weightx)

3 Answers

Solution

Output

EDIT

Solution

Output

Console

Full code