GUI RadioButtonJPanel

Question

I need to create a GUI that has red, green and blue radiobuttons. When a radiobutton is clicked they should cause a panel in the centre of the frame to change to the corresponding backcolour colour. Here is my code below: what am I doing wrong. Here is my code below(please help; it compiles but the frame appears tiny and displays nothing):

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class RadioButtons extends JFrame implements ActionListener {
    JFrame f;
    JPanel panel = new JPanel();
    JRadioButton rb1, rb2, rb3;
    JButton b1;
    JButton b2;
    JButton b3;

    public RadioButtons() {
        f = new JFrame();
        rb1 = new JRadioButton("Green");
        //rb1 = new JLabel(, JLabel.RIGHT);
        rb1.setBounds(100, 70, 100, 40);
        rb2 = new JRadioButton("Red");
        rb2.setBounds(100, 90, 100, 40);
        //rb2 = new JLabel("Red", JLabel.RIGHT);
        rb3 = new JRadioButton("Blue");
        rb3.setBounds(100, 100, 100, 40);
        //rb3 = new JLabel("Blue", JLabel.RIGHT);
        ButtonGroup s1 = new ButtonGroup();
        s1.add(rb1);
        s1.add(rb2);
        s1.add(rb3);
        this.setSize(400, 400);
        f.setLayout(null);
        f.setVisible(true);
        f.setTitle("GUI Background Changer");

        b1 = new JButton("Change background color");
        b1.setBounds(200, 200, 50, 50);
        b1.addActionListener(this);
        b2 = new JButton("Change background color");
        b2.setBounds(200, 200, 50, 50);
        b2.addActionListener(this);
        b3 = new JButton("Change background color");
        b3.setBounds(200, 200, 50, 50);
        b3.addActionListener(this);

        add(rb1);
        add(rb2);
        add(rb3);

        f.add(panel);

        //x.setDefaultCloseOperation(XFrame.EXIT_ON_CLOSE);

    }//constructor

    public static void main(String[] args) {
        RadioButtons radiobuttons = new RadioButtons();
        radiobuttons.setJpanelSize(200, 200, 50, 50);//setJPanelSize(200,200,50,50);
        radiobuttons.setDefaultCloseOperation(EXIT_ON_CLOSE);

    }// main

    public void backgroundChanged(ActionEvent e) {
        Color initialcolor1 = Color.RED;
        Color initialcolor2 = Color.BLUE;
        Color initialcolor3 = Color.GREEN;
        if (rb1.isSelected()) {
            panel.setBackground(initialcolor1);
        }// if
        else
            if (rb2.isSelected()) {
                panel.setBackground(initialcolor2);
            }// else if

            else {
                panel.setBackground(initialcolor2);
            }// else
    }

    public void setJpanelSize(int v, int w, int x, int y) {

    }// setJPanel size

    @Override
    public void actionPerformed(ActionEvent e) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

}//class

Answer 1

it compiles but the frame appears tiny and displays nothing):

That is probably because you forgot to pack your JFrame after adding the components. Invoke pack() for your frame after adding the components.

You will also want to:

1. Call setVisible(true) after all other actions.
2. Prevent from using null layout.