POLYPOLYGON

[Paul Hung]

DEAR ALL：
POLYPOLYGON IS A METHOD TO DRAWING PLOYGON INSIDE ONE POLYGON. How could I do in java?

[Steve Lovelace]

The basic trick is to subclass JPanel (I'm assuming you're using Swing) and override the paintComponent() method. Your method will use java.awt.Graphics2D.draw(Shape) to render your polypolygon. You could put draw() in a loop and iterate over a collection of polygon edges (java.awt.geom.Line2D), or you could build a java.awt.geom.GeneralPath for each polygon, inner and outer, and then invoke draw() on each one.

[Craig Wood]

import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;
 
public class DrawingPolygons
{
    public static void main(String[] args)
    {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new PolygonPanel());
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}
 
class PolygonPanel extends JPanel
{
    public PolygonPanel()
    {
        setBackground(Color.white);
    }
 
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        int w = getWidth();
        int h = getHeight();
        int R = Math.min(w,h)/10;
        int[][] xy = generateShapeArrays(w/4, h/4, R, 3);
        Polygon p = new Polygon(xy[0],xy[1],3);
        g2.draw(p);
        xy = generateShapeArrays(w*3/4, h/4, R, 4);
        p = new Polygon(xy[0],xy[1],4);
        g2.draw(p);
        xy = generateShapeArrays(w/2, h/2, R, 5);
        p = new Polygon(xy[0],xy[1],5);
        g2.draw(p);
        xy = generateShapeArrays(w/4, h*3/4, R, 6);
        p = new Polygon(xy[0],xy[1],6);
        g2.draw(p);
        xy = generateShapeArrays(w*3/4, h*3/4, R, 7);
        p = new Polygon(xy[0],xy[1],7);
        g2.draw(p);
    }
 
    private int[][] generateShapeArrays(int cx, int cy, int R, int sides)
    {
        int radInc = 0;
        if(sides % 2 == 0)
            radInc = 1;
        int[] x = new int[sides];
        int[] y = new int[sides];
        for(int i = 0; i < sides; i++)
        {
            x[i] = cx + (int)(R * Math.sin(radInc*Math.PI/sides));
            y[i] = cy - (int)(R * Math.cos(radInc*Math.PI/sides));
            radInc += 2;
        }
        // keep base of triangle level
        if(sides == 3)
            y[2] = y[1];
        return new int[][] { x, y };
    }
}