How can I limit the maximum width of labels in a Swing GroupLayout-managed form to a fraction of the parent frame's width while handling resizing?

Swing GroupLayout: Resizing and Limiting Component Sizes

Question

In a dynamically generated data input form managed by Swing's GroupLayout, how can one limit the maximum width of labels to a specific fraction of the parent frame's width, while adapting to resizing events?

Answer

To effectively limit label width using GroupLayout:

• Leverage the preferred size of the label, which naturally accommodates the largest label.
• Rely on the default behavior of components for resizing.
• Utilize GroupLayout.Alignment.TRAILING to right-justify the labels if desired.

Example Code

import javax.swing.GroupLayout;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class LabelWidthLimitPanel extends JPanel {

    private JLabel label1 = new JLabel("Primary:");
    private JTextField field1 = new JTextField(16);
    private JLabel label2 = new JLabel("Secondary:");
    private JTextField field2 = new JTextField(16);
    private JLabel label3 = new JLabel("Tertiary:");
    private JTextField field3 = new JTextField(16);

    public LabelWidthLimitPanel() {
        GroupLayout layout = new GroupLayout(this);          
        this.setLayout(layout);
        layout.setAutoCreateGaps(true);
        layout.setAutoCreateContainerGaps(true);
        layout.setHorizontalGroup(layout.createSequentialGroup()
            .addGroup(layout.createParallelGroup(GroupLayout.Alignment.TRAILING)
                .addComponent(label1)
                .addComponent(label2)
                .addComponent(label3))
            .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                .addComponent(field1)
                .addComponent(field2)
                .addComponent(field3))
        );
        layout.setVerticalGroup(layout.createSequentialGroup()
            .addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
                .addComponent(label1)
                .addComponent(field1))
            .addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
                .addComponent(label2)
                .addComponent(field2))
            .addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
                .addComponent(label3)
                .addComponent(field3))
        );
    }
}

In this example:

• GroupLayout effectively resizes the labels without manual intervention.
• The text fields are resizable, ensuring optimal use of space.
• The labels are right-justified using alignment.

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