Re-positioning the ContentPane of a JFrame

Question

I'm trying to draw a grid inside the content pane of my JFrame but when I do, everything is off. The grid starts too wide and offset (presumably set where the border of the window overlaps the contentpane) and it doesn't draw the entire grid correctly. When i use frame.setUndecorated(true); everything works perfectly.

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.*;

@SuppressWarnings("serial")
class Creator extends JFrame{

    JFrame frame;
    int[][] Grid = new int[18][27];
    public Creator(){
        frame = this;
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        for(int i = 0; i < 18; i++) {
            for(int j = 0; j < 27; j++) {
                Grid[i][j] = 0;
            }
        }
        setSize(864, 544);

        getContentPane().addMouseListener(new MouseAdapter() {            
            @Override
            public void mouseClicked(MouseEvent e) {
                int yLocation = e.getX()/32;
                int xLocation = e.getY()/32;
                System.out.println(xLocation + " " + yLocation);

                if(e.getButton() == 1){
                    if(xLocation < 1 || yLocation < 1){
                        Grid[xLocation][yLocation] = 2;
                        System.out.println("Enemy Added");
                    }else if(xLocation > 16 || yLocation > 25){
                        Grid[xLocation][yLocation] = 2;
                        System.out.println("Enemy Added");
                    }else {
                        Grid[xLocation][yLocation] = 1;
                        System.out.println("Obstacle Added");
                    }
                }else {
                    Grid[xLocation][yLocation] = 0;
                    System.out.println("Item Removed");
                }
                frame.invalidate();
                frame.validate();
                frame.repaint();
            }
        });

    }

    public void paint(Graphics g) {
        g.clearRect(0, 0, 864, 544);
        Graphics2D g2 = (Graphics2D) g;
        for(int i =0; i < 18; i++) {
            for(int j =0; j < 27; j++) {
                if(Grid[i][j] != 0){
                    if( i < 1 || j < 1 || i > 26 || j > 17) {
                        g2.setColor(Color.RED);
                        g2.fillRect(j*32, i*32, 32, 32);
                    }else {
                        g2.setColor(Color.BLUE);
                        g2.fillRect(j*32, i*32, 32, 32);
                    }
                }
                //System.out.print(Grid[i][j]);
            }
            //System.out.println();
        }
        for(int i = 0; i < 27; i++) {
            Line2D lin = new Line2D.Float(i*32, 0, i*32, 544);
            g2.draw(lin);
        }
        for(int i = 0; i < 18; i++) {
            Line2D lin = new Line2D.Float(0, i*32, 864, i*32);
            g2.draw(lin);
        }

    }

    public static void main(String []args){
        Creator s=new Creator();
        s.setVisible(true);
    }
}

Answer 1

Don't set the size of the frame.

Instead, create a subclass of JPanel or JComponent, override paintComponent() to paint your grid, and override getPreferredSize() to return the size it should have (864 x 544). Add this panel to your frame and call pack() to make sure that the frame size adjusts itself to the size needed to display its component with their preferred size.

EDIT: example:

public class GridPanel extends JPanel {
    @Override
    public void paintComponent(Graphics g) {
        // paint the grid here
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(864, 544);
    }
}

and in the JFrame constructor:

GridPanel gridPanel = new GridPanel();
this.add(gridPanel);
this.pack();

Answer 2

JB Nizet, gives you the excellent solution. Change your code as follows:

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.*;

@SuppressWarnings("serial")
class Creator extends JPanel{


    static int[][] Grid = new int[18][27];
    public Creator(){        
        setSize(getPreferredSize());
    }

    public void paint(Graphics g) {
        g.clearRect(0, 0, getWidth(), getHeight());
        Graphics2D g2 = (Graphics2D) g;
        for(int i =0; i < 18; i++) {
            for(int j =0; j < 27; j++) {
                if(Grid[i][j] != 0){
                    if( i < 1 || j < 1 || i > 26 || j > 17) {
                        g2.setColor(Color.RED);
                        g2.fillRect(j*32, i*32, 32, 32);
                    }else {
                        g2.setColor(Color.BLUE);
                        g2.fillRect(j*32, i*32, 32, 32);
                    }
                }
                //System.out.print(Grid[i][j]);
            }
            //System.out.println();
        }
        for(int i = 0; i < 27; i++) {
            Line2D lin = new Line2D.Float(i*32, 0, i*32, getHeight());
            g2.draw(lin);
        }
        for(int i = 0; i < 18; i++) {
            Line2D lin = new Line2D.Float(0, i*32, getWidth(), i*32);
            g2.draw(lin);
        }

    }

    public static void main(String []args){
        JFrame frame=new JFrame();
        Creator s=new Creator();
        frame.setSize(864, 544); 
        frame.add(s);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().addMouseListener(new MouseAdapter() {            
            @Override
            public void mouseClicked(MouseEvent e) {
                int yLocation = e.getX()/32;
                int xLocation = e.getY()/32;
                System.out.println(xLocation + " " + yLocation);

                if(e.getButton() == 1){
                    if(xLocation < 1 || yLocation < 1){
                        Grid[xLocation][yLocation] = 2;
                        System.out.println("Enemy Added");
                    }else if(xLocation > 16 || yLocation > 25){
                        Grid[xLocation][yLocation] = 2;
                        System.out.println("Enemy Added");
                    }else {
                        Grid[xLocation][yLocation] = 1;
                        System.out.println("Obstacle Added");
                    }
                }else {
                    Grid[xLocation][yLocation] = 0;
                    System.out.println("Item Removed");
                }
//                frame.invalidate();
//                frame.validate();
//                frame.repaint();
            }
        });
//        s.setUndecorated(true);
    }
}