BorderLayout not working

Question

I cannot get BorderLayout to work. I want the cancel button to be located at the bottom, but it does not work. The code:

import java.awt.BorderLayout;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.ButtonModel;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JRadioButton;

class Test {
    public static JFrame owner;
    public static void main(String[] args) {
        final JDialog frame = new JDialog(owner, "Test");
        frame.setLayout(new BorderLayout());
        frame.setSize(500, 300);
        final JPanel panel = new JPanel();
        final ButtonGroup group = new ButtonGroup();
        String[] options = {"1", "2", "3"};
        for (String text : options) {
            JRadioButton option = new JRadioButton(text);
            option.setActionCommand(text);
            group.add(option);
            panel.add(option);
        }
        JButton okButton = new JButton("OK");
        okButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                ButtonModel selectedModel = group.getSelection();
                if (selectedModel != null) {
                    System.err.println(selectedModel.getActionCommand());
                }
            }
        });
        panel.add(okButton);
        JButton cancelButton = new JButton("Cancel");
        cancelButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                frame.setVisible(false);
                frame.dispose();
            }
        });
        panel.add(cancelButton, BorderLayout.SOUTH);
        frame.add(panel);
        frame.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
        frame.setVisible(true);
    }
}

Answer 1

You can try to change

panel.add(cancelButton, BorderLayout.SOUTH);

to

frame.add(cancelButton, BorderLayout.SOUTH);

Result:

Answer 2

You add cancelButton to the panel using the BorderLayout.SOUTH constant:

  panel.add(cancelButton, BorderLayout.SOUTH);

But where do you set up the BorderLayout panel layout? Since you never installed this container layout, it will use the default layout for JPanel, which is FlowLayout.

Solution: set the JPanel panel layout to BorderLayout to get the BorderLayout behavior.

, :

  for (String text : options) {
     JRadioButton option = new JRadioButton(text);
     option.setActionCommand(text);
     group.add(option);
     panel.add(option);
  }

JRadioButton JPanel . , JRadioButtons JPanel, , , GridLayout(1, 0) GridLayout(0, 1), , JPanel , , BorderLayout.CENTER.

okButton , .

Answer 3

Hovercraft Full Of Eels , JPanel - FlowLayout, , . , :

panel = new JPanel(new BorderLayout())