applets

[eddoPCT]

can anyone help me with an applet that allows users to drag circles with the mouse?


thanks . . .

[sjalle]

It does not handle 'backwards' dragging (negative rectangles) but that i
figured you could mess with yourself

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;

/**
 * A JPanel extension for drawing and moving circles using the mouse
 *
 * I have ignored 'backwards' circles,  DIY
 *
 * @author sjalle
 * @version 1.0
 */
class DrawPanel extends JPanel implements MouseListener, MouseMotionListener {

  private ArrayList circleRectList=null; // all the rectangles for the ovals
  private Point startP=null; // mouse was last pressed at this point
  private Point endP=null; // mouse was last moved to/released at this point
  private Rectangle activeRectangle=null; // the rectangle of the currently dragged oval
  private Point dragOffset=null; // the offset between the mouse click point and an ovals top-left
  private boolean isDragging=false; // true when an oval is being dragged

  /**
   * Constructor
   */
  public DrawPanel () {
    super();
    circleRectList=new ArrayList();
    this.addMouseListener(this);
    this.addMouseMotionListener(this);
  }
  /**
   * The screen update
   * @param g
   */
  public void update (Graphics g) {
    Color c=g.getColor(); // save current context color
    /**
     * color background
     */
    g.setColor(Color.blue);
    g.fillRect(0,0,
               this.getSize().width,
               this.getSize().height);
    /**
     * draw circles
     */
    for (int i=0; i<circleRectList.size(); i++) {
      Rectangle cRect=(Rectangle)circleRectList.get(i);
      // color a dragged cirlce cyan
      if (cRect==activeRectangle) {
        g.setColor(Color.cyan);
      } else {
        g.setColor(Color.white);
      }
      g.drawOval(cRect.x,
                 cRect.y,
                 cRect.width,
                 cRect.height);

      drawOvalData(g, cRect.x,
                   cRect.y,
                   cRect.width,
                   cRect.height);

    }
    /**
     * Draw current rectangle if user is drawing, if there is an
     * activeRectangle then the user is just dragging, not drawing.
     */
    if (startP!=null && activeRectangle==null) {
      g.setColor(Color.cyan);
      g.drawOval(startP.x,
                 startP.y,
                 endP.x-startP.x,
                 endP.y-startP.y);

      drawOvalData(g, startP.x,startP.y,
                   endP.x-startP.x,
                   endP.y-startP.y);

    }
    g.setColor(c);// restore  current context color
  }
  /**
   * draw oval data
   */
  private void drawOvalData(Graphics g, int x, int y, int w, int h) {
    g.setColor(Color.yellow);
    g.drawString("( X "+x+"  Y "+y+" W "+w+" H "+h+" )", x+2, y-2);
  }
  /**
   * Remove all current circles
   */
  public void clearCircles () {
    this.circleRectList.clear();
    repaint(); // show new state
  }
  /**
   * Just do the update
   * @param g
   */
  public void paint (Graphics g) {
    update(g);
  }

  /**
   * Mouse is pressed, reset all activeRectangle values
   * @param e
   */
  public void mousePressed(MouseEvent e) {

    startP=endP=e.getPoint();
    /**
     * check if mouse is pressed down inside the rectangle of
     * an old circle (oval).
     * Scan the ld circles list and check for hit.
     */
    for (int i=0; i<circleRectList.size(); i++) {

      Rectangle r=(Rectangle)circleRectList.get(i);

      if (r.contains(e.getPoint())) {
        activeRectangle=r;
        isDragging=true;
        dragOffset=new Point(r.x-e.getPoint().x,
                             r.y-e.getPoint().y);

        break;
      }
    }
  }
  /**
   * Finish dragging/Store new cirlce in list
   * if the mouse release was preceded by mouse dragging.
   * @param e
   */
  public void mouseReleased(MouseEvent e) {

    if (startP==null)
      return; // nothing has happened since last mouseReleased

    if (activeRectangle==null) {
      /**
       * this is a newly drawn oval,
       * create the rectangle and add to ist
       */
      Rectangle r=new Rectangle (new Point(startP),
                                 new Dimension(endP.x-startP.x,
                                              endP.y-startP.y));
     if (!r.isEmpty())
       circleRectList.add(r);
    }
    repaint(); // show all circles
    /**
     * Initiate
     */
    startP=null;
    endP=null;
    activeRectangle=null;
    isDragging=false;
  }
  /**
   * Mouse is held down while moving, either a circle is being
   * drawn or a circle is being dragged
   * @param e
   */
  public void mouseDragged(MouseEvent e) {

    endP = e.getPoint();

    if (isDragging) {
      /**
       * just set the new location
       */
      activeRectangle.setLocation(e.getPoint().x+dragOffset.x,
                                  e.getPoint().y+dragOffset.y);
    } else {
      /**
       * move bottom-right corner of new oval's rectangle
       */
      endP.setLocation(e.getPoint());
    }
    repaint(); // resfresh display
  }
  /**
   * Unused mouse interface methods
   * @param e
   */
  public void mouseEntered(MouseEvent e) { }
  public void mouseExited(MouseEvent e) {  }
  public void mouseClicked(MouseEvent e) { }
  public void mouseMoved(MouseEvent e) { }
}
/**
 * Driver frame for showing a DrawPanel
 * @author sjalle
 * @version 1.0
 */
public class DrawDragCircles extends JFrame implements ActionListener {

  BorderLayout borderLayout1 = new BorderLayout();
  JPanel buttonPanel = new JPanel();
  JButton clearButton = new JButton();
  JButton closeButton = new JButton();
  DrawPanel drawPanel = new DrawPanel();

  public DrawDragCircles() {
    try {
      jbInit();
      // ensure proper program termination
      addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
          System.exit(0);
        }
      });
    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }
  /**
   * ************************* MAIN ************************
   * @param args
   */
  public static void main(String[] args) {
    DrawDragCircles ddc = new DrawDragCircles();
    ddc.setBounds(20,20,500,500);
    ddc.setVisible(true);
  }
  /**
   * Handle button clicks
   * @param e
   */
  public void actionPerformed(ActionEvent e) {
    if (e.getSource()==clearButton) {
      this.drawPanel.clearCircles();
    } else if (e.getSource()==closeButton) {
      System.exit(0);
    }
  }
  /**
   * Set up GUI (JBuilder style)
   * @throws Exception
   */
  private void jbInit() throws Exception {
    this.getContentPane().setLayout(borderLayout1);
    clearButton.setText("Clear");
    closeButton.setText("Close");
    closeButton.addActionListener(this);
    clearButton.addActionListener(this);
    buttonPanel.setBorder(BorderFactory.createEtchedBorder());
    this.getContentPane().add(buttonPanel, BorderLayout.SOUTH);
    buttonPanel.add(closeButton, null);
    buttonPanel.add(clearButton, null);
    this.getContentPane().add(drawPanel, BorderLayout.CENTER);
  }


}

[eddoPCT]

thanks for the help.

everything compiles except this line:

activeRectangle.setLocation(e.getPoint().x+dragOff set.x,e.getPoint().y+dragOffset.y);

when i compiled, the program says ')' expected and there is a ^ pointing under the x

[sjalle]

Its a little thing with the text transport here, so what you see is the word 'dragOffset'
mangled into two words: 'dragOff set'....

[eddoPCT]

thanks again for the help. i'm not that good at programming applets, you really saved me.

thanks . . .