Can't add ActionListener to JPanel?

I have tried for over an hour to test a simple program to change the color of the ball on click, when I try myPanel.addActionListener(new BallListener())

I get one error at compile time

Please help me find the error?

myPanel.addActionListener(new BallListener());
       ^
  symbol:   method addActionListener(Ball.BallListener)
  location: variable myPanel of type MyPanel
1 error





//first Java Program on the new VM
    import java.awt.*;
    import javax.swing.*;
    import java.awt.event.*;
    import java.awt.geom.*;
    import java.util.*;

    public class Ball{

    private MyFrame myFrame;
    private MyPanel myPanel;

    public static void main(String[] args)
    {
    Ball ball=new Ball();
    ball.go();

    }//main ends

    public class BallListener implements ActionListener{

    public void actionPerformed(ActionEvent e)
    {
    myFrame.repaint();
    }

    }//listener ends

    public void go()
    {

    myPanel=new MyPanel();
    //myPanel.addActionListener(new BallListener());
    myFrame=new MyFrame();
    myFrame.add(BorderLayout.CENTER,myPanel);
    myFrame.setVisible(true);
    }

    }//class ends



    //ball panel
    class MyPanel extends JPanel
    {
    public void paintComponent(Graphics g)
    {
    Graphics2D g2d=(Graphics2D)g;
    Ellipse2D ellipse=new Ellipse2D.Double(200,200,400,400);
    int r=(int)Math.random()*256;
    int b=(int)Math.random()*256;
    int g1=(int)Math.random()*256;
    Color color=new Color(r,g1,b);
    g2d.setPaint(color);
    g2d.fill(ellipse);
    }
    }//Class ends

    //a simple JFrame
    class MyFrame extends JFrame{

    public MyFrame()
    {
    setSize(600,600);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setResizable(false);
    }
    }//class ends

      

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2 answers


JPanel

do not support ActionListener

because they have no natural action. For buttons, the natural action is to click on them, so it makes sense to have ActionListener

one that fires when clicked. JPanel

are not buttons.



If you want to detect clicks on JPanel

, you need to add MouseListener

, not ActionListener

.

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for panel events, you can use WindowListener, which override WindowsClosing methods, etc. ActionListener is not used for frame or panel, etc.



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