I wrote a java program which uses a JPanel for drawing. My problem
occurs when I need to draw something that is larger than the size of
the panel on which the drawing panel is put. I'd like to enlarge the
drawing panel so that a JScrollPane would be activated - i.e. scroll
bars will appear.

I've used this nesting: JFrame -> JSplitPane -> JScrollPane -> JPanel -> DrawPanel

This whole thing should be combined in a larger program of mine. So
I've created a sample program to represent the problem.

Here I've drawn only two lines, and enforced the drawing panel's size
to be 1000x1000. The solution should enable choosing the size
dynamically, meaning - enable resizing according to the drawing area.



I've creared two *.java files:
//1: 
import javax.swing.*;
import java.awt.*;


public class MainWindow {

    private final static Dimension formSize = new Dimension(600,400);
    private final static Toolkit toolkit = Toolkit.getDefaultToolkit();
    private final static Dimension scrnSize = toolkit.getScreenSize();
    private final static Point formLoc = new
Point((scrnSize.width-formSize.width)/2,(scrnSize.height-formSize.height)/2);

    private JSplitPane vSplit;
    private JScrollPane drawScrollPane;
    private JPanel drawBasePanel;

    MainWindow() {
        vSplit = new JSplitPane();
        vSplit.setContinuousLayout(false);
        vSplit.setEnabled(true);
        vSplit.setResizeWeight(1.0);
        vSplit.setDividerSize(10);
        vSplit.setDividerLocation(170);
        vSplit.setOneTouchExpandable(false);
        drawScrollPane = new JScrollPane();
        vSplit.setRightComponent(drawScrollPane);
        drawBasePanel = new JPanel();
        drawScrollPane.setViewportView(drawBasePanel);

        JFrame frame = new JFrame("Resize Problems");

        DrawPanel drawPanel = new DrawPanel();

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        drawBasePanel.setLayout(new GridLayout(1,1));
        drawBasePanel.add(drawPanel);

        Dimension minimumSize = new Dimension(300, 300);
        drawBasePanel.setMinimumSize(minimumSize);
        drawPanel.setMinimumSize(minimumSize);
        drawBasePanel.setMinimumSize(minimumSize);

        frame.getContentPane().add(vSplit);
        frame.setSize(formSize);
        frame.setLocation(formLoc);
        frame.setVisible(true);
    }

    public static void main(String[] args){
        MainWindow mainWindow = new MainWindow();
    }
}


//2:
import javax.swing.*;
import java.awt.*;


public class DrawPanel extends JPanel {

    public void paint(Graphics graphics) {
        this.setSize(1000,1000);
        this.setBackground(Color.white);
        super.paintComponent(graphics);
        Graphics2D g2 = (Graphics2D)graphics;

        int width = this.getSize().width;
        int height = this.getSize().height;
        g2.drawLine(1, 1, width, height);

        g2.drawLine(width+50, 1, 1, height+50);
    }
}