Change buttons to a limited frame movement

Hi All,
I want to affect changes in the size of a octagon
drawn and related text size using a different method.
The program below is near what I want in that the button
clicks now resize the image drawn. I want to replace the
buttons with a detectable amount of movement in
resizing the frame then resizes the image and text size.
Do not know how to do this.
TIA
bH

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

public class ShowAPolygon extends JFrame implements
ActionListener {
    private JButton drawLgrBtn = new JButton("Draw Lgr");
    private JButton drawSmrBtn = new JButton("Draw Smlr");
    private JButton closeBtn = new JButton("Close");
    private JPanel btnPanel = new JPanel();
    private int fontSize = 12;//Message Font size
    private String msgStr = "Stop Sign Polygon";

    private static final int width = 300;// frame width
    private static final int height = 320;;// frame height
    int xPosition = 150;// repostions drawing x values
    int yPosition = 200;// repostions drawing y values
    int measureOfDiameter = 90; // image is drawn with circle
    int measureIncreaseBy = 15; // image is dia is incrsd by amt
    int measureDecreaseBy = 15; // image is dia is decrsd by amt
    int numPoints = 8;// num points needed for a octagon
    int[] xPoints = new int [numPoints];// array stores x values
                                                         //for a
polygon
    int[] yPoints = new int [numPoints];// array stores y values
                                                          //for a
polygon

    ShowAPolygon(){
        btnPanel.add(drawLgrBtn);
        drawLgrBtn.addActionListener(this);
        btnPanel.add(drawSmrBtn);
        drawSmrBtn.addActionListener(this);
        btnPanel.add(closeBtn);
        closeBtn.addActionListener(this);
        Container contentPane= getContentPane();
        contentPane.add(btnPanel);
        contentPane.setLayout( new GridLayout(1,1));
        this. setSize(width,height);
        this.setResizable(true);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == drawLgrBtn){
            measureOfDiameter = measureOfDiameter +
                  measureIncreaseBy;
            fontSize = fontSize + 1 ;
           repaint();
        }
        if(e.getSource() == drawSmrBtn){
            measureOfDiameter = measureOfDiameter -
                  measureDecreaseBy;
            fontSize = fontSize - 1 ;
            repaint();
        }
        if(e.getSource() == closeBtn){
            System.exit(0);
        }
    }

    public void paint(Graphics g) {
        super.paint(g);
        Graphics2D g2 = (Graphics2D)g;
        Color rndm= new Color((int)(Math.random()*255),
                              (int)(Math.random()*255),(int)
(Math.random()*255));
        g.setColor(rndm);
        //calculating point locations
        for (int n = 0; n <numPoints; n++) {
            xPoints[n] = (int) (xPosition + measureOfDiameter *
Math.cos
                                    ((2 * Math.PI / numPoints) * (0.5
+n) ));
            yPoints[n] = (int) (yPosition + measureOfDiameter*
Math.sin
                                     ((2 * Math.PI /numPoints) * (0.5
+ n) ));
        }

        g.fillPolygon(xPoints, yPoints, numPoints);
        g.setColor(Color.black);//accents the shape visually
        g.drawPolygon(xPoints, yPoints, numPoints);
        //for message inside the polygon
        g.setFont(new Font("Helvetica", 2, fontSize));
        g.drawString(msgStr,100,200);

    }
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                ShowAPolygon sapg = new ShowAPolygon();
            }
        });
    }
}