How Can I Limit JLabel Width in Swing's GroupLayout While Maintaining Responsiveness to Frame Resizing?

Resizing and Limiting Component Sizes in Swing GroupLayout

Swing's GroupLayout provides flexible layout management for complex user interfaces. However, controlling component sizes within a GroupLayout can be challenging when dealing with dynamic resizing. This article will present a solution to limit the maximum width of component labels in a GroupLayout while maintaining their responsiveness to frame size changes.

The Issue

Consider a GroupLayout with parallel groups for horizontal layout and a sequential group for vertical layout, as follows:

*-----------------------------------------------*
| label A     |   field A                       | 
| label B     |   field B                       |
| label C     |   field C                       |
*-----------------------------------------------*

The task is to limit the width of the labels (instances of JLabel) to one-third of the frame's width while the frame can be resized.

Solution

1. Rely on Preferred Size

Instead of manually setting size constraints, GroupLayout can utilize the preferred size of the labels. Labels have a default preferred size that adapts to their text content. By default, GroupLayout respects these preferred sizes for component resizing behavior.

2. GroupLayout Alignment

To right-justify the labels, GroupLayout.Alignment.TRAILING can be used:

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))
);

3. Example Code

The following code demonstrates the implementation of this solution:

public class GroupPanel 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 GroupPanel(int n) {

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