I was just trying to add Graphics2D to a Frame this way:

Game.java
import java.awt.Component;

public class Game
{
public static void main(String[] args)
{
MainFrame mainFrame = new MainFrame();
MainGraphics mainGraphics = new MainGraphics();
mainFrame.getContentPane().add(mainGraphics);
}
}
That file contains the main function, where I create a new frame and a new graphics (both classes made in separate files), and then I try to add the graphics to the frame.

The problem is, though, I get:

Exception in thread "main" java.lang.Error: Unresolved compilation problems:
   Cannot instantiate the type MainGraphics
   The method add(Component) in the type Container is not applicable for the arguments (MainGraphics)

I can only add components to frames and content panes.

So I tried to make mainGraphics a component, like this:

Component mainGraphics = new MainGraphics();
However, I get (in this line):

Exception in thread "main" java.lang.Error: Unresolved compilation problems:
   Type mismatch: cannot convert from MainGraphics to Component
   Cannot instantiate the type MainGraphics

Does anybody know how to solve this? Thanks! Also, MainGraphics is an abstract class, here's its code:

import java.awt.Graphics2D;


public abstract class MainGraphics extends Graphics2D {
public MainGraphics()
{
this.create();
this.drawLine(5, 5, 10, 10);
}
}


Nemo, what if I use Graphics instead of Graphics2D? The example you gave me is good, but the problem is I need my code organized in separate files, I am expecting this to be a rather large project.

Thanks for the quick response too!

Thanks nemo! I have this now:

Runner.java
public class Runner
{
    public static void main(String[] args)
    {
        new Game().run();
    }
}

Game.java
import java.awt.Graphics2D;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class Game extends JPanel
{
    JFrame mainFrame = new JFrame("Game");

public Game()
{
        mainFrame.setSize(800, 600);
    }
    public void run()
    {
        mainFrame.setVisible(true);
    }
    public void paintComponent(Graphics2D g)
    {
        super.paintComponent(g);
        g.drawLine(5, 5, 10, 10);
    }
}
Right now, my only question is adding the Graphics to the Game Panel. Thanks!

Game.java
import java.awt.Graphics2D;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class Game extends JPanel
{
    JFrame mainFrame = new JFrame("Game");

public Game()
{
        mainFrame.setSize(800, 600);
    }
    public void run()
    {
        mainFrame.setVisible(true);
    }
    public void paintComponent(Graphics2D g)
    {
        super.paintComponent(g);
        g.drawLine(5, 5, 10, 10);
    }
}
Runner.java
public class Runner
{
    public static void main(String[] args)
    {
        new Game().run();
    }
}
Well, the line I'm drawing is not appearing, do you know what's wrong? Thanks!

Hm, I tried adding this in public Game():

mainFrame.getContentPane().add(this);
So that I had the panel to the frame, but I still don't see the line.

Thanks a lot!

the exact some code is working on my computer. are you sure you saved/recompiled before you ran the code? also, what's the project you're working on?

I just created those two files and then used "javac" to compile Game.java and then Runner.java, then used "java Runner" to run the program.

@Nemo: It's no project yet, it's more like testing.

Again, you cannot add Graphics to the panel. JPanels have a Graphics instance variable already. i just noticed your method header for paintComponent is incorrect. it's parameter should be of type Graphics, not Graphics2D.