Shrink JLabel inside a GridBagLayout cell

Question

The problem

I have a JPanel with the GridBagLayout as a layout manager. I want the columns of the layout to have certain widths. Sometimes the width of a column might be lower than the preferred width of a component inside. In this case, the column should force a component to take only the available space of the column. But, for now, a component inside a cell doesn't shrink if the column width constraint is less than the component's preferred width.

Example

Below is the demo with 4x4 grid. I want the JLabel in the top-left corner to shrink in accordance with the min widths I have set when initialized GridBagLayout (10 px)

As I run the example below, the following result is obtained:

The cell in the top-left takes more space than it was allowed initially by the GridBagLayout

public class ResizeDemo extends JFrame {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            ResizeDemo resizeDemo = new ResizeDemo();
            resizeDemo.pack();
            resizeDemo.setDefaultCloseOperation(EXIT_ON_CLOSE);
            resizeDemo.setVisible(true);
        });
    }

    public ResizeDemo() {
        GridBagLayout gridBagLayout = new GridBagLayout();
        gridBagLayout.columnWidths = new int[]{0, 0};
        gridBagLayout.rowHeights = new int[]{0, 0};
        gridBagLayout.columnWeights = new double[]{1.0, Double.MIN_VALUE};
        gridBagLayout.rowWeights = new double[]{1.0, Double.MIN_VALUE};
        getContentPane().setLayout(gridBagLayout);

        JPanel panel = new JPanel();
        GridBagConstraints gbc_panel = new GridBagConstraints();
        gbc_panel.fill = GridBagConstraints.BOTH;
        gbc_panel.gridx = 0;
        gbc_panel.gridy = 0;
        getContentPane().add(panel, gbc_panel);
        GridBagLayout gbl_panel = new GridBagLayout();
        
        
        // ============  Set the column widths here ============
        //  Note that the width of the first column is 10 px 
        gbl_panel.columnWidths = new int[] {10, 150, 0};
        // =====================================================
        
        gbl_panel.rowHeights = new int[]{0, 0, 0};
        gbl_panel.columnWeights = new double[]{0.0, 0.0, 0.0};
        gbl_panel.rowWeights = new double[]{0.0, 0.0, Double.MIN_VALUE};
        panel.setLayout(gbl_panel);

        JLabel label1 = new JLabel("A very long string here");
        label1.setHorizontalAlignment(SwingConstants.CENTER);
        GridBagConstraints gbc_label1 = new GridBagConstraints();
        gbc_label1.fill = GridBagConstraints.HORIZONTAL;
        gbc_label1.gridx = 0;
        gbc_label1.gridy = 0;
        panel.add(label1, gbc_label1);

        JLabel label2 = new JLabel("Label");
        GridBagConstraints gbc_label2 = new GridBagConstraints();
        gbc_label2.gridx = 1;
        gbc_label2.gridy = 0;
        panel.add(label2, gbc_label2);

        JLabel label3 = new JLabel("Label");
        GridBagConstraints gbc_label3 = new GridBagConstraints();
        gbc_label3.fill = GridBagConstraints.HORIZONTAL;
        gbc_label3.gridx = 0;
        gbc_label3.gridy = 1;
        panel.add(label3, gbc_label3);

        JLabel label4 = new JLabel("Label");
        GridBagConstraints gbc_label4 = new GridBagConstraints();
        gbc_label4.gridx = 1;
        gbc_label4.gridy = 1;
        panel.add(label4, gbc_label4);

    }
}

Question:

How can I force the JLabel inside a GridBagLayout cell to shrink itself?

Answer 1

The GridBagLayout sizes each column based on the largest "preferred size" of any component added to the column.

The "columnWidths" is used to set the minimum value for any column. This is used when you resize the frame. If there is not enough space to display the component at it preferred size and you have set a resize weight for the component, then the component will shrink in size from its preferred size to its minimum size.

How can I force the JLabel inside a GridBagLayout cell to shrink itself?

One possibility is to wrap the label in a panel using a BoxLayout. The BoxLayout will respect the maximum size of size of the component. The basic logic would be:

//panel.add(label1, gbc_label1);
Dimension max = label1.getPreferredSize();
max.width = 10;
label1.setMaximumSize(max);
Box wrapper = Box.createHorizontalBox();
wrapper.add(label1);
panel.add(wrapper, gbc_label1);

Don't know what your real application is, but if you are only using labels, then maybe you can use a JTable. With a JTable you can control the actual column width.