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Creating a draw rectangle (filled with black color) function in Java for a grid

Asked 2013-04-08T03:01:56.357
10

I have created a grid in my program. Below is the code used to create the grid.

import java.awt.Graphics;

import javax.swing.JComponent;
import javax.swing.JFrame;

class Grid extends JComponent {
    public void paint(Graphics g) {
        g.drawRect (10, 10, 800, 500);    

        for (int i = 10; i <= 800; i+= 10)
            g.drawLine (i, 10, i, 510);

        for (int i = 10; i <= 500; i+= 10)
            g.drawLine (10, i, 810, i);
    }
}

public class CoreControl {

    public static void main(String[] a) {
        JFrame window = new JFrame();
        window.setSize(840,560);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.getContentPane().add(new Grid());
        window.setVisible(true);
    }

}

What I want to do is to create a function which will draw a rectangle (filled with black color) based on the coordinates that I give it. Basically I want to populate certain cells of the grid with black color and my idea is to draw black filled rectangles on the cell coordinates. How do I make this function?

I tried making another class called drawRectangle and called it in the main function like so window.getContentPane().add(new drawRectangle()); however that did not work (only drawRectangle shows up and not the grid).

I also want to be able to use this function repeatedly to keep creating rectangles.

How do I do create this function?

Also if you know a better way that I should structure this program please let me know (I am new to Java so I am open to any suggestions).

java swing graphics grid paint
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1 Answer

28
  1. Don't use paint, use paintComponent and don't forget to call super.paintComponent
  2. JComponent may not be the best choice, JPanel is probably a better choice
  3. What's wrong with Graphics#fillRect(int, int, int, int)?

You might to take a look at Performing Custom Painting and 2D Graphics for more details.

I'd advice against trying to have a second component to performing the filling. Simply provide a method in you grid class that supplies the cell's x/y position (in grid terms) and fill the cell within the paintComponent method

Updated with example

enter image description here

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Point;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class CoreControl {

    public static class Grid extends JPanel {

        private List<Point> fillCells;

        public Grid() {
            fillCells = new ArrayList<>(25);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            for (Point fillCell : fillCells) {
                int cellX = 10 + (fillCell.x * 10);
                int cellY = 10 + (fillCell.y * 10);
                g.setColor(Color.RED);
                g.fillRect(cellX, cellY, 10, 10);
            }
            g.setColor(Color
answered 2013-04-08T03:05:43.533

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