Question

I would like to rotate pie chart about his center, how can I do this? I would like to rotate whole pie chart. This is my code:

import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.util.Random;
import javax.swing.JComponent;
import javax.swing.JFrame;

class Slice{

    double value;
    Color color;
    public Slice(double _value){
        Random numGen = new Random();
        int R =  numGen.nextInt(256);
        int G = numGen.nextInt(256);
        int B = numGen.nextInt(256);
        this.setColor(new Color(R,G,B));
        this.value = _value;    
    }
    public void setColor(Color _color){
        this.color = _color;

    }
}



class Component extends JComponent {

    int movx = 0;
    int movy = 0;
    private double angle = 0;
    private double radius = 0.0D;
    private  Random numGen;
    private int w = 500;
    private int h = 500;



    Slice[] slice = {new Slice(5),new Slice(20),new Slice(33),new Slice(42)};
    public Component(){
        numGen = new Random();
        Listener listener = new Listener();
        addMouseListener(listener);
        addMouseMotionListener(listener);
    }

    class Listener extends MouseAdapter{
        private double LastAngle;
        @Override
        public void mousePressed(MouseEvent e) {
            LastAngle = getAngle(e.getPoint());
        }
        @Override
        public void mouseDragged(MouseEvent e) {
            double curAngle = getAngle(e.getPoint());
            double deltaAngle = curAngle - LastAngle;
            angle += deltaAngle;
            repaint();
            LastAngle = curAngle;
        }
        private double getAngle(Point point) {
            double x = point.getX() - 0.5 * 500;
            double y = point.getY() - 0.5 * 500;
            return Math.atan2(y, x);
        }

    }

    public void paint(Graphics g){
        Graphics2D g2 = (Graphics2D)g;
       //g2.translate(250, 250);
        g2.rotate(angle,w/2-5,h/2-5);
        drawPie(g2, getBounds(), slice);

    }
    public void drawPie(Graphics2D g, Rectangle area, Slice[] s){
        double total = 0.0D;

        //calculate total value
        for(int i=0;i<s.length;i++)
            total+=s[i].value;
       radius = total/2*Math.PI;
        double curentValue = 0.0D;
        int startAngle = 0; 
        for(int i = 0;i<s.length;i++){

            //s[i].setColor(new Color(numGen.nextInt(256), numGen.nextInt(256), numGen.nextInt(256)));
            startAngle = (int)((curentValue*360)/total);
            int arcAngle = (int)((s[i].value*360)/total) ;
            g.setColor(s[i].color);
            //g.rotate(angle);//row AA
           for(int j=1;j>0;j--){
            g.fillArc(j, j, w, h, startAngle, arcAngle);   

           }
            curentValue+=s[i].value;

        }
    }


}

public class PieChart {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        JFrame frame = new JFrame();
        frame.getContentPane().add(new Component());
        frame.setSize(600,600);
        frame.setVisible(true);
    }
}

How can I do this. I write w/2,h/2, because in fillArc I write width and heght 500, but it not rotate about the center.

Answer 1

You are using

g2.rotate(angle,w/2-5,h/2-5);

which will rotate the pie chart about an off-center point. You could use:

g2.rotate(angle, (w / 2) + 1, (h / 2) + 1);