Switching colors in a GUI

Question

ok so i am trying to make a small java paint program but i am having trouble trying to get my buttons to work. I was able to get one color when i instantiated the MyPanel class, but i changed it around in an attempt to make use of my buttons. I basically have it setup to where each button activates a certain constructor in the MyPanel class and each constructor activates the appropriate methods to change the colors so I can draw. Im really new to programming so any advice you guys could give me would be much appreciated. I also have an extra class that is instantiated in the MyPanel class which i didnt bother putting in because i know the problem isnt in there. All the Red class does is set the color

import javax.swing.SwingUtilities;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseMotionAdapter;

public class Driver
{
public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() 
    {
        public void run() {
            createAndShowGUI();
        }
    });


}

private static void createAndShowGUI()
{
    SwingUtilities.isEventDispatchThread();
    JFrame frame = new JFrame();
    JPanel panel = new JPanel();

    JButton red = new JButton("red");
    JButton blue = new JButton("blue");

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.add(panel);
    frame.setVisible(true);
    frame.pack();
    frame.setSize(1000,1000);

    panel.add(red);
    panel.add(blue);
    blue.addActionListener( new Action() );
    red.addActionListener( new Action() );

}
}//end driver class
public class Action implements ActionListener 
{

    public void actionPerformed( ActionEvent e )
    {
    MyPanel d = new MyPanel(); 

    }

}//end Action
public class MyPanel extends JPanel
{
    private int xCoord = 50;
    private int yCoord = 50;
    private int squareW = 20;
    private int squareH = 20;

    Red red = new Red();

    public MyPanel()
    {

         setBorder(BorderFactory.createLineBorder(Color.yellow));

        addMouseListener(new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                moveSquarer(e.getX(),e.getY());
            }
        });

        addMouseMotionListener(new MouseAdapter() {
            public void mouseDragged(MouseEvent e) {
                moveSquarer(e.getX(),e.getY());
            }
         });

   }
private void moveSquare(int x, int y) 
    {

        if ((xCoord != x) || (yCoord!= y)) {
            repaint(xCoord,yCoord,squareW+1,squareH+1);

            red.setX(x);
            red.setY(y);

            repaint(red.getX(),red.getY(),red.getWidth()+1,red.getLength()+1);
        } 
    }

public void paintComponent(Graphics g) {

         super.paintComponent(g);
         g.drawString("hi",10,20);
         red.paintSquare(g);


    }  //end MyPanel

Answer 1

I basically have it setup to where each button activates a certain constructor in the MyPanel class and each constructor activates the appropriate methods to change the colors so I can draw.

I can't see it since your ActionListener is the same for both buttons:

private static void createAndShowGUI() {
    ...
    blue.addActionListener( new Action() );
    red.addActionListener( new Action() );
    ...
}

public class Action implements ActionListener {
    @Override
    public void actionPerformed( ActionEvent e ) {
        MyPanel d = new MyPanel();
    }
}

This method doesn't even add this new panel to the frame so it will never be visible.

Also what is this object?

Red red = new Red();

Suggested approach

You may follow this suggested tips to achieve your goal:

• Provide MyClass with a method to set the desired color.
• Add an instance of this panel (or many as needed) to the frame when you initialize your GUI. Note: this/these may be added dinamically but you need to follow the hints about adding components to a displayed container described here
• Use action listener to set the panel color as you whish.

For instance:

public class MyPanel extends JPanel {

    private Color color = Color.red;
    // this color should be used within paintComponent() method

    public void setColor(Color newColor) {
        color = newColor;
        repaint();
    }

    ...
}