how can i repaint using different colors in a separate method?

Question

I am trying to use my fillCell method to be able to change the color based on what color was put in the parameter, however i dont know how to utilize graphics to change the color and repaint it and i am not importing objectdraw for this. I am trying to do this for a snake game i am trying to create. The class is meant to draw the grid, color the snake's body and head as well as clear the end of the snake and color the obstacles . So far i have:

import java.awt.*;
import java.util.ArrayList;
import javax.swing.*;
import java.awt.event.*;
public class GraphicsGrid extends JPanel
{
    private ArrayList<Point> fillCells;
    private int wid, hei, pix;
/**
 * Creates an arraylist and sets the default width, height and pixel
 * for a grid.
 */
    public GraphicsGrid() {
        fillCells = new ArrayList<Point>();
        wid = 400;
        hei = 400;
        pix = 10;
    }
/**
 * Creates an arraylist and sets the inputted width, height and pixel
 * for a grid.
 * @param width size of the width for the grid
 * @param height size of the height for the grid
 * @param pixel size for each cell 
 */ 
    public GraphicsGrid(int width, int height, int pixel) {
        fillCells = new ArrayList<Point>();
        wid = width;
        hei = height;
        pix = pixel;
    }
/**
 * fills and paints the current cell and creates the grid with lines
 * @param g creates an instance of graphics that has been imported
 */
    @Override
    protected synchronized void paintComponent(Graphics g) {
        super.paintComponent(g);
        for (Point fillCell : fillCells) {
            int cellX = (fillCell.x * pix);
            int cellY = (fillCell.y * pix);
            g.setColor(Color.GREEN);
            g.fillRect(cellX, cellY, pix, pix);
        }
        g.setColor(Color.BLACK);
        g.drawRect(0, 0, wid*pix, hei*pix);    

        for (int i = 0; i < wid*pix; i += pix) {
            g.drawLine(i, 0, i, hei*pix);
        }    

        for (int i = 0; i < hei*pix; i += pix) {
            g.drawLine(0, i, wid*pix, i);
        }
    }
/* *
 * adds a point to the cell and repaints the cell
 * @param x x-coordinate of the cell
 * @param y y-coordinate of the cell
 */
    public void fillCell(int x, int y, Color block) {
        Graphics g = new Graphics();
        super.paintComponent(g);
        fillCells.add(new Point(x, y));
        if(block.equals("black"))
        {
            g.setColor(Color.BLACK);
            repaint();
        }
        else if(block.equals("red"))
        {
            g.setColor(Color.RED);
            repaint();
        }
        else if(block.equals("white"))
        {
            g.setColor(Color.WHITE);
            repaint();
        }
        else
        {
            g.setColor(Color.Green);
            repaint();
        }
        repaint();
    }

I cannot create another class file for this program either.

Answer 1

Graphics g = new Graphics(); Graphics is an abstract class, and so this will never work.

Suggestions:

• Create a Cell class, give it a Point and a Color field and any other fields it needs, and give it any getters/setters/constructors that it needs.
• Give Cell a draw(Graphics g) method that allows it to draw itself using its own Point's x and y and Color fields.
• Give your class above an ArrayList<Cell> and fill it as needed.
• In your paintComponent method override, iterate through the ArrayList above, calling draw(g) on each Cell in the ArrayList.
• I'm not sure why you've made your paintComponent method synchronized but that looks a bit sketchy to me, and I recommend that you get rid of that key word.
• Only call the super.paintComponent(g) method within the paintComponent override method.
• Have you gone through the Graphics tutorials yet? If not I suggest you do so soon. You can find them at this link.