Dragging a Window

Question

Hello,
I am trying to create a window which can be dragged along the screen using the mouse. The source is as follows:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
public class WindowTest extends Window
implements MouseMotionListener {
   int xDrag = 0;
   int yDrag = 0;
   int x = 0;
   int y = 0;
   int xPos = 0;
   int yPos = 0;
   boolean firstDrag = true;
   public WindowTest(Frame parent) {
      super(parent);
      this.addMouseMotionListener(this);
      this.setSize(200,200);
      this.setBackground(Color.black);
      this.setLocation(200,200);
      this.show();
   public void mouseDragged(MouseEvent e) {
      if( firstDrag) {
         System.out.println("first");
         xDrag = e.getX();
         yDrag = e.getY();
         firstDrag = false;
      else {
         System.out.println("second");
         xPos = (int)(this.getLocation()).getX();
         yPos = (int)(this.getLocation()).getY();
         x = e.getX() - xDrag;
         y = e.getY() - yDrag;
         xDrag = e.getX() - x;
         yDrag = e.getY() - y;
         xPos = xPos + x;
         yPos = yPos + y;
         this.setLocation(xPos,yPos);
         firstDrag = true;
   public void mouseMoved(MouseEvent e){}
   public static void main( String[] args) {
      new WindowTest( new Frame());
}This code works fine when I drag the frame for the first time, however, when I attempt to drag it for a second time the frame positions itself so that the mouse pointer is in the same place as the original drag (try running my code to understand what I mean). How can I correct this bug - any suggestions?
Thank you for your time.

Answer 1

Hmm, I'm not sure why you were checking for the first drag or not, check for a mouse press instead. I used inner classes because I got lazy and didn't want to write out all the methods, but the same thing applies if you want to implement both listeners. Here's the modified code:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
public class WindowTest extends Window {
   int x = 0;
   int y = 0;
   int xPos = 0;
   int yPos = 0;
   public WindowTest(Frame parent) {
      super(parent);
      this.setSize(200,200);
      this.setBackground(Color.black);
      this.setLocation(200,200);
      this.show();
      addMouseListener(new MouseAdapter() {
          public void mousePressed(MouseEvent e) {
          x = e.getX();
             y = e.getY();
          addMouseMotionListener(new MouseMotionAdapter() {
         public void mouseDragged(MouseEvent e) {
            setLocation(getLocation().x+(e.getX()-x),
            getLocation().y+(e.getY()-y));
   public static void main( String[] args) {
      new WindowTest( new Frame());
}