Repainting a graphic paintComponent using an ActionListener

I am struggling a bit with how to repaint a circle graphic to a different color on a button click. Further, I also have to do the same with a JColorChooser. Getting the chooser dialog to show is fairly straightforward but what do I need to add to the action listener to get the color of the circle changed?

I am kind of at a loss, though I know that the method repaint() is involved. Please have a look at my code and tell me where I am going wrong or "painting" myself into a corner. Thanks!

package P3;

// ******************************************************************
//   CirclePanel.java
//
//   A panel with a circle drawn in the center and buttons on the 
//   bottom that move the circle.
// ******************************************************************
import java.awt.*;
import java.awt.Graphics;
import javax.swing.*;
import java.awt.event.*;

public class CirclePanel extends JPanel {

    public JButton btnChoice;
    private JButton btnRed;
    private JButton btnYellow;
    private JButton btnBlue;
    private final int CIRCLE_SIZE = 50;
    private int x, y;
    private Color c;

    //---------------------------------------------------------------
    // Set up circle and buttons to move it.
    //---------------------------------------------------------------
    public CirclePanel(int width, int height) {
        // Set coordinates so circle starts in middle
        x = (width / 2) - (CIRCLE_SIZE / 2);
        y = (height / 2) - (CIRCLE_SIZE / 2);
        //set recentering coordinates - need to find a position relative to
        //center of panel and not location of circle (for position reset)

        c = Color.green;

        // Need a border layout to get the buttons on the bottom
        this.setLayout(new BorderLayout());

        // Create buttons to move the circle
        JButton left = new JButton("Left");
        JButton right = new JButton("Right");
        JButton up = new JButton("Up");
        JButton down = new JButton("Down");
        JButton center = new JButton("+");

        // Add listeners to the buttons
        left.addActionListener(new MoveListener(-20, 0));
        right.addActionListener(new MoveListener(20, 0));
        up.addActionListener(new MoveListener(0, -20));
        down.addActionListener(new MoveListener(0, 20));
        //reset circle position to start position
        //center.addActionListener(new MoveListener());

        // Need a panel to put the buttons on or they'll be on top of each other.
        GridBagLayout layout = new GridBagLayout();
        // create GridBagConstraints object "gbc" to position the buttons we want to use
        GridBagConstraints gbc = null;

        //position of up button
        gbc = new GridBagConstraints();
        gbc.gridx = 1;
        gbc.gridy = 0;
        gbc.insets = new Insets(0, 0, 3, 0);
        layout.setConstraints(up, gbc);
        //position of left button
        gbc = new GridBagConstraints();
        gbc.gridy = 1;
        gbc.insets = new Insets(0, 0, 0, 3);
        layout.setConstraints(left, gbc);
        //position of center button
        gbc = new GridBagConstraints();
        gbc.gridx = 1;
        gbc.gridy = 1;
        layout.setConstraints(center, gbc);
        //position of right button
        gbc = new GridBagConstraints();
        gbc.gridx = 2;
        gbc.gridy = 1;
        gbc.insets = new Insets(0, 3, 0, 0);
        layout.setConstraints(right, gbc);
        //position of down button
        gbc = new GridBagConstraints();
        gbc.gridx = 1;
        gbc.gridy = 2;
        gbc.insets = new Insets(3, 0, 0, 0);
        layout.setConstraints(down, gbc);

        // apply GridBagLayout to a JPanel
        JPanel btnPanel = new JPanel(layout);
        //add the buttons to the panel
        btnPanel.add(left);
        btnPanel.add(right);
        btnPanel.add(up);
        btnPanel.add(down);
        btnPanel.add(center);

        //new panel with buttons to choose colors
        JPanel chooserBtnPnl = new JPanel();
        chooserBtnPnl.setLayout(new GridLayout(1, 4, 3, 3));
        //red button
        btnRed = new JButton("Red");
        btnRed.setBackground(c.RED);
        btnRed.addActionListener(new ColorListener(Color.RED));
        //yellow button
        btnYellow = new JButton("Yellow");
        btnYellow.setBackground(c.YELLOW);
        btnYellow.addActionListener(new ColorListener(Color.YELLOW));
        //blue button
        btnBlue = new JButton("Blue");
        btnBlue.setBackground(c.BLUE);
        btnBlue.addActionListener(new ColorListener(Color.BLUE));
        //button used for choosing a color with JColorChooser
        btnChoic开发者_运维技巧e = new JButton("Choose Color");
        btnChoice.addActionListener(new ColorListener());

        chooserBtnPnl.add(btnRed);
        chooserBtnPnl.add(btnYellow);
        chooserBtnPnl.add(btnBlue);
        chooserBtnPnl.add(btnChoice);

        // Add the chooser panel to the top of the main panel
        this.add(chooserBtnPnl, "North");
        // Add the button panel to the bottom of the main panel
        this.add(btnPanel, "South");

    }


    //---------------------------------------------------------------
    // Draw circle on CirclePanel
    //---------------------------------------------------------------
    public void paintComponent(Graphics page) {
        super.paintComponent(page);
        page.setColor(c);
        page.fillOval(x, y, CIRCLE_SIZE, CIRCLE_SIZE);
    }

    //---------------------------------------------------------------
    // Class to listen for button clicks that move circle.
    //---------------------------------------------------------------
    private class MoveListener implements ActionListener {

        private int dx;
        private int dy;
        //---------------------------------------------------------------
        // Parameters tell how to move circle at click.
        //---------------------------------------------------------------

        public MoveListener(int dx, int dy) {
            this.dx = dx;
            this.dy = dy;
        }
        //---------------------------------------------------------------
        // Change x and y coordinates and repaint.
        //---------------------------------------------------------------

        public void actionPerformed(ActionEvent e) {
            x += dx;
            y += dy;
            repaint();
        }
    }

    private class ColorListener implements ActionListener {

        private Color color;

         ColorListener(){}
        //tells what color to change the circle to
        public ColorListener(Color c) {
            this.color = c;
        }

        //change color and repaint
        public void actionPerformed(ActionEvent e) {

            JColorChooser jcc = new JColorChooser();
            if (e.getSource() == btnChoice) {
                jcc.showDialog(btnChoice, "Choose Circle Color", Color.BLUE);


            } else {
                if (e.getSource() == btnRed) {
                    repaint();
                } else if (e.getSource() == btnYellow) {
                    repaint();
                } else if (e.getSource() == btnBlue) {
                    repaint();
                }

            }
        }
    }
}

and file MoveCircle.java

package P3;

// ******************************************************************
//   MoveCircle.java
//
//   Uses CirclePanel to display a GUI that lets the user move
//   a circle by pressing buttons.
// ******************************************************************
import java.awt.*;
import javax.swing.*;

public class MoveCircle {

    public static void main(String[] args) {
        JFrame frame = new JFrame("MoveCircle");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500,500);
        frame.getContentPane().add(new CirclePanel(400,300));
        frame.setLocationRelativeTo(null);
        frame.setResizable(false);
        frame.setVisible(true);

    }
}

Actually you forgot to set the new color to your field c (the color the circle is painted) in your ColorListener. The following code should do the trick.

    // change color and repaint
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == btnChoice) {
            JColorChooser jcc = new JColorChooser();
            c = jcc.showDialog(btnChoice, "Choose Circle Color", Color.BLUE);
        } else {
            c = this.color;
        }
        repaint();
    }