Int value in MousePressed in one JPanel not updating when the Int changes

Question

I'm coding an application to print bricks in the grids, and I have set it up so that ideally, to change the colour, the menu selection changes an int which sets the colour in the bricks class.

I have two panels, one for the grid (where things are drawn) and one for the menu bar. If I manually change the number in the grid, it works, so I think it might be a problem with the menu, but I'm not sure. I'm wondering how I can get the int from the menu jpanel to the grid jpanel whenever it changes.

This is the menu code:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Selector extends JPanel implements Common, ActionListener{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    public Color colorValues[] = {Color.BLACK, Color.YELLOW, Color.RED, Color.ORANGE};
    public String colors[] = {"Black", "Yellow", "Red", "Orange"};
    public JMenuItem colorItems[];
    public int display;

    //constructor
    public Selector(){
        //set size and layout
        setPreferredSize(new Dimension(SELECTOR_WIDTH, SELECTOR_HEIGHT));
        setLayout(new BorderLayout());

        //menu bar
        JMenuBar bar = new JMenuBar();
        Font f = new Font("Helvetica", Font.BOLD, 15);

        //menus
        JMenu colorMenu = new JMenu("Colour");

        //create Color menu
        String colors[] = {"Black", "Yellow", "Red", "Orange"};
        colorItems = new JMenuItem[colors.length];

        for (int i = 0; i<colors.length; i++){
            colorItems [i] = new JMenuItem(colors[i]);
            colorMenu.add(colorItems[i]);
            colorItems[i].addActionListener(this);
        }// end of for loop


        //set all font the same
        UIManager.put("Menu.font", f);
        UIManager.put("MenuBar.font", f);
        UIManager.put("MenuItem.font", f);

        //add menus
        bar.add(colorMenu);

        //add menu bar
        add(bar, BorderLayout.PAGE_START);

    }//constructor end

    public void actionPerformed(ActionEvent e){

        if (e.getSource()==colorItems[0]){
            display=0;
        }
        else if (e.getSource()==colorItems[1]){
            display=1;
        }
        else if (e.getSource()==colorItems[2]){
            display=2;
        }
        else if (e.getSource()==colorItems[3]){
            display=3;
        }
    }
}//class end

This is the Map Grid code:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MapGrid extends JPanel implements Common, MouseListener{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    //brick array
    public Bricks [] brick = new Bricks[COLUMN*ROW];

    //number array to save
    public int [] cell = new int[COLUMN*ROW];

    //coordinate variables
    private int x=0;
    private int y=0;

    Selector s = new Selector();

    //constructor
    public MapGrid(){
        //sets size, layout, and background colour
        setPreferredSize(new Dimension(MAPGRID_WIDTH, MAPGRID_HEIGHT));
        setLayout(new GridLayout(ROW, COLUMN));

        addMouseListener(this);

        //draws grid of bricks
        for (int i = 0; i <COLUMN*ROW; i++){
            cell[i] = 4;
            if ((i%COLUMN==0)&&(i>COLUMN-1)){
                x=0;
                y+=22;
            }
            brick[i] = new Bricks(x,y);
            x+=40;
        }
    }//constructor end

    //draws bricks
    public void paint(Graphics g){
        super.paint(g);
        for (int i = 0; i <COLUMN*ROW; i++){
            brick[i].draw(g);
        }
    }//paint end

    public void mousePressed(MouseEvent evt) {
        //gets mouse  and y coordinates
        int x = evt.getX();
        int y = evt.getY();

        //gets column and row of mouse location
        int c =x/BRICK_WIDTH;
        int r =y/BRICK_HEIGHT;

        //checks if mouse is within range
        if ((c>=0&&c<=COLUMN)&&(r>=0&&r<=ROW)){
            int index = (r)*COLUMN+c; //calculates brick number

            //right click - delete brick
            if (evt.isMetaDown()) {
                brick[index].setChoice(4);
                cell[index]=4;
            }
            //left click - draws brick
            else{
                brick[index].setChoice(s.display);
                cell[index]=s.display;
            }
        }
        repaint();
    }//mousePressed end

    //unused
    public void mouseEntered(MouseEvent evt) {}  
    public void mouseExited(MouseEvent evt) {}   
    public void mouseClicked(MouseEvent evt) {}  
    public void mouseReleased(MouseEvent evt) {}
}//class end

this is the brick code:

import java.awt.*;

public class Bricks implements Common{

    //variables
    public int x=0;
    public int y=0;
    public int choice=3;
    public boolean clear = true;

    //size of bricks
    private static final int width = BRICK_WIDTH;
    private static final int height = BRICK_HEIGHT;

    //constructor
    public Bricks(int x, int y){
        this.x=x;
        this.y=y;
    }//constructor end

    //draw bricks
    public void draw(Graphics g){
        //set color or blank
        switch(choice){
            case 0: g.setColor(Color.BLACK);
                break;
            case 1: g.setColor(Color.YELLOW);
                break;
            case 2: g.setColor(Color.RED);
                break;
            case 3: g.setColor(Color.ORANGE);
                break;
            case 4: clear = true;
                break;
        }

        //check if set blank
        if (clear==true){
            g.setColor(Color.BLACK);
            g.drawRect(x,y,width,height);
        }
        else{
            g.fillRect(x,y,width,height);
        }
    }//draw end

    //set choice of color
    public void setChoice (int c){
        choice=c;
        clear = false;
    }//choice end
}//class end

Answer 1

Your problem is here:

public class MapGrid extends JPanel implements Common, MouseListener{
    //...

    Selector s = new Selector();  // ******* HERE **********

    // ...

    public void mousePressed(MouseEvent evt) {
        // ....

            else{
                brick[index].setChoice(s.display);
                cell[index]=s.display;
            }
        // ....
    }

    //...
}

You're creating a new Selector object above, but it is likely completely distinct from the Selector object that is displayed in your GUI. So changes to the state of the Selector held and displayed by the GUI will not be reflected in the Selector object that you're using above.

To solve this, make sure that the Selector variable refers to the one and same Selector that is displayed in the GUI.

e.g., change it to something like so:

public class MapGrid extends JPanel implements Common, MouseListener{
    //...

    Selector s = null;

    public MapGrid(Selector s) {
      this.s = s;
    }

    // .... etc....

and then when you create your MapGrid object, be sure to pass in a reference to the displayed true Selector instance.