Java BoxLayout Issue [duplicate]

Question

This question already has answers here:

How can I align all elements to the left in JPanel? (3 answers)

Closed 9 years ago.

I encountered an issue that I can't seem to resolve while programming the preferences panel in my Java Swing application.

SSCCE:

import java.awt.BorderLayout;
import java.awt.Dimension;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSeparator;
import javax.swing.JTabbedPane;

/**
 * demonstrates the issue at hand
 */
public class Probs extends JFrame {
    /**
     * 
     */
    private static final long serialVersionUID = -2320457631507860940L;
    JCheckBox one = new JCheckBox("Checkbox One");
    JCheckBox two = new JCheckBox("Checkbox Two");
    JCheckBox three = new JCheckBox("Checkbox Three");
    JCheckBox four = new JCheckBox("Checkbox Four");

    final static int BORDER = 10;
    final static int WIDTH = 440;
    final static int DESC_HEIGHT = 30;

    public Probs () {
        JTabbedPane options = new JTabbedPane();
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //set up the main panel
        JPanel pan = new JPanel();
        pan.setBorder(BorderFactory.createEmptyBorder(Probs.BORDER, Probs.BORDER, Probs.BORDER, Probs.BORDER));
        pan.setLayout(new BoxLayout(pan, BoxLayout.Y_AXIS));

        //construct the descriptor subpanel
        JPanel desc = new JPanel();
        desc.setLayout(new BorderLayout());
        desc.add(new CustomLab("Options Title Goes Here"));
        JSeparator sep1 = new JSeparator();
        desc.add(sep1, BorderLayout.SOUTH);
        desc.setPreferredSize(new Dimension(Probs.WIDTH, Probs.DESC_HEIGHT));
        desc.setMinimumSize(new Dimension(Probs.WIDTH, Probs.DESC_HEIGHT));
        desc.setMaximumSize(new Dimension(Probs.WIDTH, Probs.DESC_HEIGHT));
        pan.add(desc);

        //basic options
        JPanel basic = new JPanel();
        basic.setLayout(new BoxLayout(basic, BoxLayout.Y_AXIS));
        basic.setBorder(BorderFactory.createTitledBorder("Basic"));
        basic.add(one);
        basic.add(two);
        basic.add(three);
        basic.add(four);
        basic.setPreferredSize(new Dimension(Probs.WIDTH, basic.getPreferredSize().height));
        basic.setMinimumSize(new Dimension(Probs.WIDTH, basic.getPreferredSize().height));
        basic.setMaximumSize(new Dimension(Probs.WIDTH, basic.getPreferredSize().height));
        pan.add(basic);

        options.addTab("Panel One", pan);
        add(options);
        setSize(500, 500);
        setVisible(true);
    }

    public static void main(String[] args) {
        new Probs();
    }
}

On my machine (OSX Mountain Lion with Java 7), that produces a result similar to this. I would like to have the Basic panel all the way to the left (and I already tried basic.setAlignmentX(JComponent.LEFT_ALIGNMENT); to no avail (that line of code had no effect). Furthermore, I already checked out questions such as

• this one
• and this one

to no avail as well.
On an interesting note, if the desc panel is removed (so pan.add(desc); is commented out), the basic panel then aligns correctly as can be seen .

How to properly left-align the desc and basic jpanels (as well as anything else you see wrong in the code).
Finally, (on a bit of a tangent): is specifying the minimum, maximum, and preferred sizes the proper way to size a JPanel in BoxLayout (it seems very inelegant)?

Answer 1

Set the alignment x of both components added to the BoxLayout using container to Component.LEFT_ALIGNMENT:

    JPanel desc = new JPanel();

    // ....

    desc.setAlignmentX(Component.LEFT_ALIGNMENT); 

    // ......

    pan.add(desc);

    JPanel basic = new JPanel();

    // ..........

    basic.setAlignmentX(Component.LEFT_ALIGNMENT);
    pan.add(basic);

---

Edit

I've just reviewed your links, and this was already mentioned in BOTH of them. So how did this not work for you? I guess this question will/should be closed as a duplicate.