Question

I have a problem with drawing a polygon in Java applet. I don’t understand what is wrong with this code. I have a class called DrawPoly that contains:

import java.awt.*;
import java.awt.geom.Point2D;
import java.applet.Applet;
import java.util.Vector;

public class DrawPoly extends Applet{
Polygon poly;
public void init(Graphics g){

        Polygon poly=new Polygon();
        poly.addPoint(60,100);

}
public void paint(Graphics g)
{
    Graphics2D gg;
    gg=(Graphics2D) g;
     System.out.println("number is"+ poly.npoints);
    }
 }

I don’t understand why the following code doesn’t work. I would like to create a global polygon, initialize it in init, and then do some 2D transformations such as rotation in paint. What am I missing? I only added one point to see if the initializations are corect. I don’t want to initialize the polygon in paint(), because i may want to use repaint() and the polygon would be initialized every time i call repaint(). If you could please help me out. Thanks a lot.

Answer 1

/* <applet code='DrawPoly' width=200 height=110></applet> */
import java.awt.*;
import java.applet.Applet;

public class DrawPoly extends Applet {

    Polygon poly;

    // init(Graphics) is not an applet method
    //public void init(Graphics g){
    @Override
    public void init() {
        // this declaration is creating a variable local
        // to the init() method
        //Polygon poly=new Polygon();
        poly=new Polygon();
        poly.addPoint(60,100);
        // at least add a 2nd point!
        poly.addPoint(160,60);
    }

    public void paint(Graphics g) {
        Graphics2D gg;
        gg=(Graphics2D) g;
        System.out.println("number is"+ poly.npoints);
        // the Polygon is never painted!
        gg.setColor(Color.BLACK);
        gg.drawPolygon(poly);
    }
}