Parallel dragging

[Olaf Enulfson]

Hello coders,


I'm experimenting with mouseListeners and I have an interesting problem (I think). I've searched the forum for similar posts but found none. Sorry if I missed any.

In my program I'm trying to move parts of shapes by dragging one of its points. I've already implemented the mousePressed() and mouseDragged() methods, and I can move single points. But I need to find out how many pixels the mouse pointer moved in X and Y and in which direction, so that I can apply the same vector to the other points.

In the mouseWheelEvent there is a method called getWheelRotation(), which returns the direction of the wheel. I need something alike for X and Y, instead of the actual new position getX() and getY() are returning.


Any thoughts? Thanks a bunch in advance,

O.
--
Sex is an emotion in motion.
-- Mae West

[pete stein]

Olaf Enulfson wrote:In my program I'm trying to move parts of shapes by dragging one of its points. I've already implemented the mousePressed() and mouseDragged() methods, and I can move single points. But I need to find out how many pixels the mouse pointer moved in X and Y and in which direction, so that I can apply the same vector to the other points.

One way is to simply have your Mouse input listener or mouse adapter save the location of the mouse on mousePressed method and store this in a variable local to this listener. Then it is trivial to calculate the change in x and y from this point in the mouseDragged method.

[pete stein]

Olaf Enulfson wrote:I'm trying to move parts of shapes

Also, much will depend on the details of just what you are trying to do. If you are trying to move a complete shape, then you may wish to use the Shape interface and affinetransforms. Otherwise you could encapsulate your shape yourself, and give it a move method. For instance:

SimpleBox.java

import java.awt.Color;
import java.awt.Graphics;

public class SimpleBox {
   private int x;
   private int y;
   private int width;
   private int height;
   private Color color;
   
   public SimpleBox(int x, int y, int width, int height, Color color) {
      this.x = x;
      this.y = y;
      this.width = width;
      this.height = height;
      this.color = color;
   }
   public int getX() {
      return x;
   }
   public void setX(int x) {
      this.x = x;
   }
   public int getY() {
      return y;
   }
   public void setY(int y) {
      this.y = y;
   }
   public int getWidth() {
      return width;
   }
   public void setWidth(int width) {
      this.width = width;
   }
   public int getHeight() {
      return height;
   }
   public void setHeight(int height) {
      this.height = height;
   }
   public Color getColor() {
      return color;
   }
   public void setColor(Color color) {
      this.color = color;
   }
   
   public void paint(Graphics g) {
      g.setColor(color);
      g.fillRect(x, y, width, height);
   }
   
   public boolean contains(int x2, int y2) {
      if (x2 >= x && x2 <= x + width && y2 >= y && y2 <= y + height) {
         return true;
      } else {
         return false;
      }
   }
   
   public void deltaMove(int deltaX, int deltaY) {
      x += deltaX;
      y += deltaY;
   }
   
   public void move(int x, int y) {
      this.x = x;
      this.y = y;
   }

}

DragBoxPanel.java

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import javax.swing.*;

@SuppressWarnings("serial")
public class DragBoxPanel extends JPanel {
   private static final Color[] COLORS = {
      Color.black, Color.white, Color.red, Color.orange, Color.yellow,
      Color.green, Color.blue, Color.magenta
   };
   private static final int SIDE = 50;
   private static final int MAIN_SIDE = 600;
   private static final Dimension MAIN_SIZE = new Dimension(MAIN_SIDE, MAIN_SIDE);
   private List<SimpleBox> boxes = new ArrayList<SimpleBox>();
   private Random random = new Random();
   
   public DragBoxPanel() {
      setPreferredSize(MAIN_SIZE);
      setBackground(Color.darkGray);
      for (Color color : COLORS) {
         int x = random.nextInt(MAIN_SIDE - SIDE);
         int y = random.nextInt(MAIN_SIDE - SIDE);
         SimpleBox box = new SimpleBox(x, y, SIDE, SIDE, color);
         boxes.add(box);
      }
      
      MyMouseListener mymListener = new MyMouseListener();
      addMouseListener(mymListener);
      addMouseMotionListener(mymListener);
   }
   
   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      for (SimpleBox box : boxes) {
         box.paint(g);
      }
   }
   
   private class MyMouseListener extends MouseAdapter {
      private SimpleBox selectedBox = null;
      private Point delta = null;
      
      @Override
      public void mousePressed(MouseEvent e) {
         selectedBox = null;
         delta = null;
         for (int i = boxes.size() - 1; i >= 0; i--) {
            SimpleBox box = boxes.get(i);
            if (box.contains(e.getX(), e.getY())) {
               selectedBox = box;
               delta = new Point(e.getX() - box.getX(), e.getY() - box.getY());
               return;
            }
         }
      }
      
      @Override
      public void mouseReleased(MouseEvent e) {
         selectedBox = null;
         delta = null;
      }
      
      @Override
      public void mouseDragged(MouseEvent e) {
         if (selectedBox != null) {
            selectedBox.move(e.getX() - delta.x, e.getY() - delta.y);
            DragBoxPanel.this.repaint();
         }
      }
   }
   
   private static void createAndShowUI() {
      JFrame frame = new JFrame("DragBoxPanel");
      frame.getContentPane().add(new DragBoxPanel());
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            createAndShowUI();
         }
      });
   }
}

[Olaf Enulfson]

Pete, you are incredible.

I came up with your first suggestion too. I feel kind of bad for posting the question so soon. I should have given it more thought first.
But your second post blew me away. You're in a league of your own.

Thanks man. I appreciate it.

O.