source: liacs/se/RouteGUI/src/routegui/Compass.java@ 143

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package routegui;

import java.awt.Graphics;
import javax.swing.JPanel;

/**
 *
 * @author rick
 */
public class Compass  extends JPanel {
         private int angle = 0;
         private int margin = 10;
         
    @Override public void paintComponent(Graphics g) {
         super.paintComponent(g);    // paints background
         int height = this.getHeight();
         int width = this.getWidth();
         g.drawOval(margin, margin, 
                    height - (2 * margin),  width - (2 * margin));
         /* Make 0 degrees act like north */
         double angle_rad = (angle - 90) * 2.0 * Math.PI/360.0;
         int len = (height / 2) - 2 * margin;
         int xMiddle = width / 2;
         int yMiddle = height / 2;
                
         g.drawLine(xMiddle, yMiddle, 
                    xMiddle + (int)(Math.cos(angle_rad) * len) , 
                    yMiddle + (int)(Math.sin(angle_rad) * len));
    }
    public void setAngle(int angleNew) {
        angle = angleNew;
        this.repaint();
    }
    
    public void setMargin(int marginNew) {
         margin = marginNew;
         this.repaint();
    }
}