How to call repaint() from one panel for another panel

Question

I have two classes (leftPanel and rightPanel), which extends JPanel. I have added these panels to the container of the JFrame. I have a JButton in my left leftPanel. When I click the button I want that the repaint method of rightPanel is called. Please tell me how to do that.

Answer 1

Ok, the reason it wasn't working is because the two classes don't have a reference to each other. They don't have anything in common at all. The only class hooking them together is the myFrame. Therefore, myFrame is the class that should be the communication link. I've added a few lines of code to myFrame, but didn't change the other classes. Now myFrame has an actionListener and it listens for the leftPanel.leftButton. When the leftButton fires, myFrame tells rightPanel to repaint. Another cool way would be to have an actionListener on rightPanel and register that with leftPanel when you instantiate them in myFrame.
GL
kimoS
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.awt.event.*;
import java.util.*;
public class myFrame extends JFrame implements ActionListener{
leftPanel left;
rightPanel right;
static int st=0;
myFrame(){
left=new leftPanel();
left.leftButton.addActionListener(this);
right=new rightPanel();
this.getContentPane().add(left,BorderLayout.WEST);
this.getContentPane().add(right,BorderLayout.CENTER);
public static void main(String args[]){
myFrame mf=new myFrame();
mf.setSize(500,500);
mf.setVisible(true);
public void actionPerformed(ActionEvent e){
right.repaint();
class leftPanel extends JPanel {
JButton leftButton;
leftPanel(){
leftButton=new JButton("leftButton");
this.add(leftButton);
leftButton.addActionListener(new leftButtonListener());
class leftButtonListener implements ActionListener{
public void actionPerformed(ActionEvent e){
myFrame.st=myFrame.st+1;
System.out.println("st value inside listener="+myFrame.st);
// ??? here I want to call repaint method of rightPanel
class rightPanel extends JPanel{
int flag=-1;
public void paintComponent(Graphics g) {
update(g);
public void update(Graphics g){
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
g2.drawString("If " myFrame.st" increases then repaint() called on click of button",30,100);
flag=flag*(-1);
if(flag==1){
g2.drawString(" painting is working",100,200);
}