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Old November 2nd, 2006, 06:20 PM
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Default Moving an ellipse

I have a GUI that is designed to let the user draw lines, curves, rectangles, circles, text, and ELLIPSES. I have modified each class so they can be moved, but i cant figure out how to modify the ELLIPSE sub class.

Below i have the Element.java class and its LINE and ELLIPSE sub class (i didnt include all of the sub classes because its too long).
I just need to know what to do to modify the ELLIPSE sub class so i can move the ellipses.

______________

Element.java
______________

import java.awt.Color;
import java.awt.Shape;
import java.awt.Point;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.geom.Line2D;
import java.awt.geom.Rectangle2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.GeneralPath;
import java.awt.geom.AffineTransform;

public abstract class Element {
  public Element(Color color) {
    this.color = color;
  }

  public Color getColor() {
    return color;
  }

  // Set or reset highlight color
  public void setHighlighted(boolean highlighted) {
    this.highlighted = highlighted;
  }

  // Get the current position of the element
  public Point getPosition() {
    return position;
  }

  // Draw an element in a given graphics context
  protected void draw(Graphics2D g2D, Shape element) {
    g2D.setPaint(highlighted ? Color.MAGENTA : color); // Set the element color
    AffineTransform old = g2D.getTransform(); // Save the current transform
    g2D.translate(position.x, position.y); // Translate to position
    g2D.draw(element); // Draw the element
    g2D.setTransform(old); // Restore original transform
  }

  protected java.awt.Rectangle getBounds(java.awt.Rectangle bounds) {
    AffineTransform at = AffineTransform.getTranslateInstance(position.x,
                                                              position.y);
    return at.createTransformedShape(bounds).getBounds();
  }

  // Move an element
  public void move(int deltax, int deltay) {
    position.x += deltax;
    position.y += deltay;
  }

  public abstract java.awt.Rectangle getBounds();
  public abstract void modify(Point start, Point last);
  public abstract void draw(Graphics2D g2D);

  protected Color color; // Color of a shape
  protected boolean highlighted = false; // Highlight flag
  final static Point origin = new Point(); // Point 0,0
  protected Point position; // Element position

  // Nested class defining a line
  public static class Line extends Element {
    public Line(Point start, Point end, Color color) {
      super(color);
      position = start;
      line = new Line2D.Double(origin, new Point(end.x - position.x, end.y - position.y));
    }

    public void draw(Graphics2D g2D) {
      draw(g2D, line); // Call base draw method
    }

    // Obtain the rectangle bounding the line
    public java.awt.Rectangle getBounds() {
      return getBounds(line.getBounds());
    }

    // Change the end point for the line
    public void modify(Point start, Point last) {
      line.x2 = last.x - position.x;
      line.y2 = last.y - position.y;
    }

    private Line2D.Double line;
  }

  public static class Ellipse extends Element {
    public Ellipse(Point center, Point corner, Color color) {
      super(color);

      // Width is twice the difference between the x coordinates of center and corner
      // Height is twice the difference between the y coordinates
      ellipse = new Ellipse2D.Double(center.x<corner.x ? 2*center.x-corner.x : corner.x,
                                    center.y<corner.y ? 2*center.y-corner.y : corner.y,
                                    2.*Math.abs(center.x-corner.x), 2.*Math.abs(center.y-corner.y) );

    }

    public void draw(Graphics2D g2D) {
      draw(g2D, ellipse);
    }

    public java.awt.Rectangle getBounds() {
      return getBounds(ellipse.getBounds());
    }

    public void modify(Point center, Point corner) {
      ellipse.x = center.x<corner.x ? 2*center.x-corner.x : corner.x;
      ellipse.y = center.y<corner.y ? 2*center.y-corner.y : corner.y;
      ellipse.width = 2.*Math.abs(center.x-corner.x);
      ellipse.height = 2.*Math.abs(center.y-corner.y);
    }

    private Ellipse2D.Double ellipse;
  }
}

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