Drawing java grid using swing

Question

I want to draw a grid(10x10) using java,but we have to implement it using drawRectMethod in a JFrame,This is my program so far

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

public class Grid extends JFrame {

    public Grid() {
        setSize(500, 500);
        setVisible(true);
    }

    // draw grid
    public void paint(Graphics g) {
        for (int x = 30; x <= 300; x += 30)
            for (int y = 30; y <= 300; y += 30)
                g.drawRect(x, y, 30, 30);
    }

    public static void main(String args[]) {
        Grid application = new Grid();
        application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

This program does not give a output, am i missing something? — Mariyam Mohammed Jalil, Dec 02 '15 at 06:28
Looks good so far, but you shouldn't be extending from `JFrame` and overriding it's `paint` method — MadProgrammer, Dec 02 '15 at 06:28
Read http://www.oracle.com/technetwork/java/painting-140037.html — Leet-Falcon, Dec 02 '15 at 06:36

score 1 · Accepted Answer · answered Dec 02 '15 at 06:36

This code is working.

Just remove 25

import java.awt.*;
 import javax.swing.*;
 public class Grid extends JFrame {

 public Grid()    {       
 setSize( 500, 500 );
 setVisible( true );   
 } 
public void paint( Graphics g )    
 {  
 for ( int x = 30; x <= 300; x += 30 )
 for ( int y = 30; y <= 300; y += 30 ) 
 g.drawRect( x, y, 30, 30 );

 } 
 public static void main( String args[] ) 
 {
     Grid application = new Grid();
 application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );   }  }

score 1 · Answer 2 · edited May 23 '17 at 10:31

I'm not sure what your question is, but your implementation is slightly off...

Don't extend from JFrame, you're not adding any new functionality to the class and it's not a good candidate for performing custom painting against, as it's not double buffered and it has a JRootPane and contentPane between frame's surface and the user. Also, you run the risk of painting under the frames decorations. Have a look at How can I set in the midst? and How to get the EXACT middle of a screen, even when re-sized for more details.
Don't override paint of top level containers (or generally), see the previous point. Instead, start with a component which extends from something like JPanel and override paintComponent instead. Also don't forget to call the paint methods super method in order to maintain the paint chain contract. Have a look at Painting in AWT and Swing and Performing Custom Painting for more details
Don't rely on magic numbers, instead, use known values to make decisions about what you want to do.

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

public class Grid {

    public static void main(String[] args) {
        new Grid();
    }

    public Grid() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            int size = Math.min(getWidth() - 4, getHeight() - 4) / 10;
            int width = getWidth() - (size * 2);
            int height = getHeight() - (size * 2);

            int y = (getHeight() - (size * 10)) / 2;
            for (int horz = 0; horz < 10; horz++) {
                int x = (getWidth() - (size * 10)) / 2;
                for (int vert = 0; vert < 10; vert++) {
                    g.drawRect(x, y, size, size);
                    x += size;
                }
                y += size;
            }
            g2d.dispose();
        }

    }
}

Drawing java grid using swing

2 Answers2

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