button in jpanel should change background of jframe?

[Chris Song]

Hello I have created 2 classes

First class is a jpanel and it has a button

Second class is a jframe and displays an object of jpanel.

I wrote this program so that i can understand object oriented programming.

My question is How can i change the jframe background colour by clicking the button that is in the jpanel class?

Could somebody provide me with a similar example. I would really apreciate it.

Thanks

[Michael Dunn]

this changes the color of the containing JPanel of the main class, not the
JFrame itself.

I've included 2 ways
1) passing a reference of the parent class to the child class
2) just using getParent()

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class MainApp extends JFrame
{
  JPanel frame = new JPanel();
  public MainApp()
  {
    setLocation(300,200);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    frame.setPreferredSize(new Dimension(400,300));
    frame.add(new MyPanel(this));
    getContentPane().add(frame);
    pack();
  }
  public static void main(String args[]){new MainApp().setVisible(true);}
}
class MyPanel extends JPanel
{
  MainApp mainFrame;
  Color[] colors = {Color.WHITE,Color.BLUE,Color.RED,Color.YELLOW,Color.BLACK};
  int colorNum = 0;
  public MyPanel(MainApp ma)
  {
    mainFrame = ma;
    setLayout(new BorderLayout());
    setPreferredSize(new Dimension(150,75));
    add(new JLabel("Hello World",SwingConstants.CENTER),BorderLayout.NORTH);
    JButton btn = new JButton("Change color");
    btn.addActionListener(new ActionListener(){
      public void actionPerformed(ActionEvent ae){
        colorNum = (colorNum+1) % colors.length;
        //mainFrame.frame.setBackground(colors[colorNum]);}});
        getParent().setBackground(colors[colorNum]);}});
    add(btn,BorderLayout.SOUTH);
  }
}