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Thread: Dragging and Dropping Rectangle - GUI

  1. #1
    Junior Member
    Join Date
    Jun 2011
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    Default Dragging and Dropping Rectangle - GUI

    I'm writing a program that displays a GUI with two rectangles ... upon clicking inside the area of either rectangle, the user should be able to drag the rectangle wherever they like, during which time, the color of the rectangle should change - but it should go back to its original color upon declicking. I can get my rectangle to move, but I cannot get it to change color. What should I do?

    import javax.swing.*;
    import java.awt.*;
    import java.awt.event.*;
    public class ColorPanel extends JPanel{
    private Rectangle r1, r2, r3;
    private Rectangle selectedRectangle; // Used to track selected shape
    private int x, y ; // Used to track mouse coordinates 
    public ColorPanel(Color backColor){
    r1 = new Rectangle(5, 5, 25, 25, Color.red);
    r2 = new Rectangle(50, 50, 25, 25, Color.blue);
    selectedRectangle = null; 
    addMouseListener(new PanelListener());
    addMouseMotionListener(new PanelMotionListener());
    public void paintComponent(Graphics g){
    if (selectedRectangle == null)
    private class PanelListener extends MouseAdapter{
    public void mousePressed(MouseEvent e){
    x = e.getX();
    y = e.getY();
    if (r1.containsPoint(x, y)){
    selectedRectangle = r1;
    else if (r2.containsPoint(x, y)){
    selectedRectangle = r2; 
    public void mouseReleased(MouseEvent e){
    x = e.getX();
    y = e.getY();
    selectedRectangle = null;
    private class PanelMotionListener extends MouseMotionAdapter{
    public void mouseDragged(MouseEvent e){
    int newX = e.getX();
    int newY = e.getY();
    int dx = newX - x;
    int dy = newY - y;
    if (selectedRectangle == r1){
    selectedRectangle.move(dx, dy);
    x = newX;
    y = newY; 

  2. #2
    Grand Poobah
    Join Date
    Mar 2011
    My Mood
    Thanked 167 Times in 158 Posts

    Default Re: Dragging and Dropping Rectangle - GUI

    I assume Rectangle is a custom class. If so does it have a setColor method? If so how about setting its colour inside your Listener classes.

  3. #3
    Forum old-timer
    Join Date
    Nov 2008
    Faversham, Kent, UK
    My Mood
    Thanked 58 Times in 54 Posts

    Default Re: Dragging and Dropping Rectangle - GUI

    Have you considered the Swing Drag & Drop framework which provides facilities for this kind of thing?

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