Develop Reference

Java Graphics Only Paint on Button Click

I'm not sure how java graphics work. It seems
to be executing something itself so I am trying to break it
down.
I'm trying to create the blank JPanel and then only draw to it
once the JButton has been clicked but it doesn't work
import javax.swing.*;
import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
public class testGui {
// global ======================================================================
static gui gc_gui;
// main ========================================================================
public static void main(String[] args) {
gc_gui = new gui();
gc_gui.cv_frame.setVisible(true);
listeners();
}
// action listeners ============================================================
public static void listeners() {
ActionListener ll_square = new ActionListener() {
public void actionPerformed(ActionEvent event) {
gc_gui.cv_content.draw(graphic);
}
};
gc_gui.cv_button.addActionListener(ll_square);
}
// gui =========================================================================
public static class gui {
JFrame cv_frame;
JButton cv_button;
content cv_content;
public gui() {
cv_frame = new JFrame();
cv_frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
cv_frame.setTitle("Test GUI");
cv_frame.setSize(600, 400);
cv_frame.setLayout(new FlowLayout());
cv_button = new JButton("Square");
cv_content = new content();
cv_content.setBackground(Color.BLACK);
cv_content.setPreferredSize(new Dimension(500, 300));
cv_frame.add(cv_button);
cv_frame.add(cv_content);
}
}
// content =====================================================================
public static class content extends JPanel {
public void paint(Graphics graphic) {
super.paint(graphic);
}
public void update() {
super.repaint();
}
public void draw(Graphics graphic) {
Graphics2D graphic2D = (Graphics2D) graphic;
graphic2D.setPaint(Color.RED);
graphic2D.fillRect(10, 10, 100, 100);
}
}
}
I create the content JPanel without the draw function being
called and then I try to call it using my ActionListener
although it is crashing because of the graphic variable.
What is the correct way to use the java graphics utility?
UPDATE
Maybe I'm not asking this question right but it is possible to
create a blank image.
Then draw additional images to that images (squares) after a button
has been clicked?
not just updating the dimensions using global variables but generating
new images to that existing image

but it is possible to create a blank image. Then draw additional images to that images (squares) after a button has been clicked?
Check out Custom Painting Approaches for two common ways to do painting.
The example allows you to draws Rectangles with the mouse. In your case the logic will be simpler as you would just invoke the addRectangle(...) method when you click a button. Of course you need to set the size/location of the Rectangle somehow.

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.LineBorder;
public class TestGui {
public static Content content;
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setTitle("Test GUI");
frame.setSize(429, 385);
frame.getContentPane().setLayout(null);
JButton cv_button = new JButton("Square");
cv_button.setBounds(10, 159, 70, 23);
frame.getContentPane().add(cv_button);
cv_button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
Content.isToDraw = true;
content.paintImmediately(content.getBounds());
Content.isToDraw = false;
}
});
JButton cv_buttonClear = new JButton("Clear");
cv_buttonClear.setBounds(10, 179, 70, 23);
frame.getContentPane().add(cv_buttonClear);
cv_buttonClear.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
content.paintImmediately(content.getBounds());
}
});
content = new Content();
content.setBorder(new LineBorder(new Color(0, 0, 0)));
content.setBounds(87, 11, 287, 312);
frame.getContentPane().add(content);
frame.setVisible(true);
}
}
class Content extends JPanel {
public static Boolean isToDraw = false;
public void paintComponent(Graphics arg0) {
if (isToDraw) {
arg0.setColor(Color.RED);
arg0.fillRect(0, 0, getWidth(), getHeight());
} else {
super.paintComponent(arg0);
}
}
}

Gui does not paint the panel

hi guys i have wird problem i have here my GUI class is working good at begining just by showing loggin screen. but i have second class called DataLayer that is responsible for reading from files and creating objets with infromaton.
the problem is that when i try to create new DataLayer() in GUI class the panel doesn show until i resize screen and even after that the keylistener doesn't work.
`package View;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JPanel;
import dto.DataLayer;
import dto.ProductDTO;
public class GUI extends JPanel {
private DataLayer dt;
private ComponentAbstract korzen;
private GUI self;
public GUI() {
this.setFocusable(true);
this.dt=new DataLayer();`
self=this;
this.stworz_PanelLogowania();
this.addKeyListener(new KeyAdapter() {
#Override
public void keyPressed(KeyEvent e) {
korzen.tryPressKey(e);
repaint();
}
});
this.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
super.mouseClicked(e);
korzen.tryClick(e.getX(), e.getY());
repaint();
}
});
this.repaint();
}
#Override
protected void paintComponent(Graphics g ) {
super.paintComponent(g);
korzen.repaint();
System.out.println("omatko");
korzen.draw((Graphics2D)g);
}
private void zmien_panel(ComponentAbstract newkorzen){
korzen=newkorzen;
self.repaint();
}
private void stworz_PanelLogowania(){
LinearPanel lp=new LinearPanel(220, 10, 300, 300);
lp.setOrientarion(Orientation.VERTICAL);
LinearPanel labels_panel=new LinearPanel(220,0,50,80);
labels_panel.setOrientarion(Orientation.VERTICAL);
labels_panel.addComponent(new Label(0, 0, 350, 40, "Witamy w castorama APP"));
lp.setPadding(6);
LinearPanel textpanel1=new LinearPanel(0, 0, 350, 80);
textpanel1.setPadding(0);
textpanel1.addComponent(new Label(0,0,350,40,"Login:"));
textpanel1.addComponent(new TextBox(0, 0, 350, 40));
LinearPanel textpanel2=new LinearPanel(0, 0, 35, 80);
textpanel2.setPadding(0);
textpanel2.addComponent(new Label(0,0,350,40,"Hasło:"));
textpanel2.addComponent(new TextBox(0, 0, 350, 40));
lp.addComponent(labels_panel);
lp.addComponent(textpanel1);
lp.addComponent(textpanel2);
LinearPanel buttons_panel=new LinearPanel(00, 00, 350, 40);
buttons_panel.setOrientarion(Orientation.HORIZONTAL);
buttons_panel.addComponent(new Button(170,40,"Zaloguj"){
#Override
public void onClick() {
TextBox tlogin=(TextBox)korzen.getComponent(1).getComponent(1);
TextBox tpass=(TextBox)korzen.getComponent(2).getComponent(1);
if(dt.autoryzacja_uzytkownika(tlogin.getText(), tpass.getText())){
System.out.println("Puszczamy typa");
}
}
});
buttons_panel.addComponent(new Button(170,40,"Wyjdz"){
#Override
public void onClick() {
System.exit(0);
}
});
lp.addComponent(buttons_panel);
korzen=lp;
System.out.println("kuniec");
}
private void stworz_panelGlowny(){
LinearPanel glowny=new LinearPanel(220,0,50,80);
}
}

the problem is that when i try to create new DataLayer() in GUI class the panel doesn show until i resize screen
When you add (or remove) components from a visible GUI the basic code is:
panel.add(...);
panel.revalidate(); // to invoke the layout manager
panel.repaint(); // to paint the components.
even after that the keylistener doesn't work.
Probably because some other component has focus and KeyEvents area only dispatched to the component with focus. Try using the requestFocusInWindow() method on the panel.
panel.requestFocus

Java JLayeredPane doesn't show it's elements

I am trying to use JLayeredPane to overlay one JPanel on top of another. For some reason the added panels don't show up.
This is the code that creates the JLayeredPane and adds elements to it:
import java.awt.BorderLayout;
import java.awt.Dimension;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLayeredPane;
import javax.swing.SwingUtilities;
public class CarAnimator extends JFrame {
public CarAnimator()
{
JLayeredPane racingOverlay = new JLayeredPane();
CarAnimatorJPanel animation = new CarAnimatorJPanel();
Racetrack racetrack = new Racetrack();
racingOverlay.add(racetrack,JLayeredPane.DEFAULT_LAYER);
racingOverlay.add(animation,new Integer(2));
racingOverlay.setBorder(BorderFactory.createTitledBorder("Can't see a thing"));
this.getContentPane().add(racingOverlay,BorderLayout.CENTER);
this.setLocationByPlatform(true);
this.setPreferredSize(new Dimension(850,650));
this.setMaximumSize(new Dimension(850,650));
this.setMinimumSize(new Dimension(850,650));
this.setResizable(false);//prevents user from resizing the window
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.pack();
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(() -> {
(new CarAnimator()).setVisible(true);
});
}
}
This is the code for the racing track JPanel:
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
public class Racetrack extends JPanel
{
Graphics g = this.getGraphics();
#Override
public void paintComponent(Graphics g)
{
Color c1 = Color.green;
g.setColor( c1 );
g.fillRect( 150, 200, 550, 300 ); //grass
Color c2 = Color.black;
g.setColor( c2 );
g.drawRect(50, 100, 750, 500); // outer edge
g.drawRect(150, 200, 550, 300); // inner edge
Color c3 = Color.yellow;
g.setColor( c3 );
g.drawRect( 100, 150, 650, 400 ); // mid-lane marker
Color c4 = Color.white;
g.setColor( c4 );
g.drawLine( 425, 500, 425, 600 ); // start line
}
}
And this is the JPanel animation example, taken from Java: How to Program book (http://java.uom.gr/~chaikalis/javaLab/Java_HowTo_9th_Edition.pdf), adapted to work with my code:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.Timer;
public class CarAnimatorJPanel extends JPanel
{
protected ImageIcon images[];
private int currentImage=0;
private final int ANIMATION_DELAY=50;
private int width;
private int height;
private Timer animationTimer;
public CarAnimatorJPanel()
{
try
{
File directory = new File("C://Users/eltaro/Desktop/Car images");
File[] files = directory.listFiles();
images = new ImageIcon[files.length];
for (int i=0;i<files.length;i++)
{
if (files[i].isFile())
{
images[i]=new ImageIcon(ImageIO.read(files[i]));
}
}
width = images[0].getIconWidth();
height = images[0].getIconHeight();
}
catch(java.io.IOException e)
{
e.printStackTrace();
}
}
#Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
images[currentImage].paintIcon(this,g,0,0);
if(animationTimer.isRunning())
{
currentImage=(currentImage+1)%images.length;
}
}
public void startAnimation()
{
if(animationTimer==null)
{
currentImage=0;
animationTimer=new Timer(ANIMATION_DELAY, new TimerHandler());
animationTimer.start();
}
else
{
if(!animationTimer.isRunning())
{
animationTimer.restart();
}
}
}
public void stopAnimation()
{
animationTimer.stop();
}
#Override
public Dimension getMinimumSize()
{
return getPreferredSize();
}
#Override
public Dimension getPreferredSize()
{
return new Dimension(width,height);
}
private class TimerHandler implements ActionListener
{
#Override
public void actionPerformed(ActionEvent actionEvent)
{
repaint();
}
}
}
When I add the two JPanels to the JLayeredPane inside CarAnimator constructor, they fail to show:

Some recommendations:
Since I'm guessing that your CarAnimatorJPanel sits on top of a background JPanel, you'd better set CarAnimatorJPanel to be non-opaque via setOpaque(false) so that the JPanel behind it can be seen.
When adding components to a JLayeredPane, you're essentially adding the components to a null layout. This means that you absolutely need to set the sizes (or override getSize()) of those components, not the preferred sizes.
As always, when dealing with image files, debug that you're able to adequately read in the image in a separate small test program. As usual, consider getting the image in as a resource and not as a File.
You have some program logic code in your paintComponent(Graphics g) method -- you change the state of the currentImage field. Never do this since you never have full control over when or even if paintComponent is called. This bit of code belongs in your animation loop, your Swing Timer's ActionListener.

Java Graphics, changing the color of drawings using click event

Ok so basically I'm trying to write a GUI application which draws 2 circles and 2 rectangles in its main window. I'm trying to get it so that whenever the user clicks within the circles or rectangles, that particular circle or rectangle changes to another random colour.
Currently I've got it so that the MouseClick event (anywhere on screen) causes all of the circles or rectangles to change colour, to the same colour.
This is what I've got so far:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Point;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Random;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Question2 {
public static void main(String[] args) {
SecondFrame f = new SecondFrame("Draw and Fill");
f.init();
}
}
class SecondFrame extends JFrame{
SecondFrame(String title) {
super(title);
}
private JPanel mainPanel;
private GridBagConstraints gbc = new GridBagConstraints();
private GridBagLayout gbLayout = new GridBagLayout();
void init() {
mainPanel = new JPanel();
mainPanel.setLayout(gbLayout);
this.setExtendedState(JFrame.MAXIMIZED_BOTH);
this.setContentPane(mainPanel);
gbc.gridheight = 1;
mainPanel.addMouseListener(new MouseListener(){
#Override
public void mouseClicked(MouseEvent e) {
Point mousePosition;
mousePosition = mainPanel.getMousePosition();
repaint();
}
#Override
public void mouseEntered(MouseEvent e) {
}
#Override
public void mouseExited(MouseEvent arg0) {
// TODO Auto-generated method stub
}
#Override
public void mousePressed(MouseEvent arg0) {
// TODO Auto-generated method stub
}
#Override
public void mouseReleased(MouseEvent arg0) {
// TODO Auto-generated method stub
}
});
this.pack();
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
}
public void paint(Graphics g){
super.paint(g);
Random ran = new Random();
// Assumes max and min are non-negative.
int red = 0 + ran.nextInt(255 - 0 + 1);
int green = 0 + ran.nextInt(255 - 0 + 1);
int blue = 0 + ran.nextInt(255 - 0 + 1);
Color myColor = new Color(red,green,blue);
g.setColor(myColor);
g.fillOval(50,50,200,200);
g.fillOval(50, 255, 200, 200);
g.fillRect(255,50,200,200);
g.fillRect(255, 255, 200, 200);
}
}
If you could point me in the right direction that would be much appreciated. Thanks.

You would keep a track of drawn object. Then check if click occurred within any of these objects. If yes, change its color. For example, you can use Shape to represent simple forms. Its contains() method can be useful to determine if a clicked point is inside the boundary of the shape. Below is an example that introduces ShapeItem that has two properties Shape and Color. And, a panel that uses a list of ShapeItem to paint the actual shapes.
Also consider some minor side notes:
Don't paint directly on top level container such as JFrame. Instead, use JPanel or extension of JComponent;
For painting override paintComponent() rather than paint(), and don't forget to call super.paintComponent(g);
Usually there is no need to extend JFrame unless new functionality is added;
Take a look at Performing Custom Painting tutorial, and Closer Look at the Paint Mechanism section in particular, for more details.
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Shape;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class DemoShapes {
public static final Color DEFAULT_COLOR = Color.BLUE;
public DemoShapes() {
List<ShapeItem> shapes = new ArrayList<ShapeItem>();
shapes.add(new ShapeItem(new Rectangle2D.Double(110, 1, 100, 100),
DEFAULT_COLOR));
shapes.add(new ShapeItem(new Rectangle2D.Double(110, 110, 100, 100),
DEFAULT_COLOR));
shapes.add(new ShapeItem(new Ellipse2D.Double(1, 1, 100, 100),
DEFAULT_COLOR));
shapes.add(new ShapeItem(new Ellipse2D.Double(1, 110, 100, 100),
DEFAULT_COLOR));
JFrame frame = new JFrame("Shapes");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
ShapesPanel panel = new ShapesPanel(shapes);
frame.add(panel);
frame.setLocationByPlatform(true);
frame.pack();
frame.setVisible(true);
}
class ShapeItem {
private Shape shape;
private Color color;
public ShapeItem(Shape shape, Color color) {
super();
this.shape = shape;
this.color = color;
}
public Shape getShape() {
return shape;
}
public void setShape(Shape shape) {
this.shape = shape;
}
public Color getColor() {
return color;
}
public void setColor(Color color) {
this.color = color;
}
}
class ShapesPanel extends JPanel {
private List<ShapeItem> shapes;
private Random rand = new Random();
public ShapesPanel(List<ShapeItem> shapesList) {
this.shapes = shapesList;
addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
Color color = getRandomColor();
for (ShapeItem item : shapes) {
if (item.getShape().contains(e.getPoint())) {
item.setColor(color);
}
}
repaint();
}
});
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
for (ShapeItem item : shapes) {
g2.setColor(item.getColor());
g2.fill(item.getShape());
}
g2.dispose();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
private Color getRandomColor() {
return new Color(rand.nextFloat(), rand.nextFloat(),
rand.nextFloat());
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new DemoShapes();
}
});
}
}

You should use mousePosition to determine if that point is within the bounds of any ovals or rectangles. If it is, perform g.setColor(myColor) and fill that shape. Then change g to a normal, non-randomized color, and fill the rest of the shapes.

Drawing on JPanel behind GlassPane when clicking on GlassPane

Okay So I looked through multiple forums and Google and couldn't find an answer to my specific problem. So I have two panels stacked on top of each other and the one on top is a glassPane. When you drag your mouse around the glassPane it draws a vertical red line at the cursor,which works, but when I click on the glassPane I want it it draw a black line at the cursor position on the panel below the glassPane. I can get it to redirect the mouseClick to the bottom panel but it wont draw the line. It just makes the redline disappear until you move the mouse again. Also If I set the glassPane invisible and click on the bottom panel the line is drawn so the drawing code works just fine. Thanks in advance.
Main Class
import java.awt.AWTException;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.Robot;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Line2D;
import java.awt.event.MouseMotionAdapter;
import java.util.ArrayList;
public class LiveField extends JPanel {
/**
* Create the panel.
*/
static JFrame frame;
static JPanel ContentPane;
private JPanel panel;
private MyGlassPane glassPane;
public static void main(String[] args) throws AWTException
{
LiveField live = new LiveField();
frame.setVisible(true);
}
public LiveField() throws AWTException {
frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(1000, 433);
setLayout(new BorderLayout(0, 0));
ContentPane = new JPanel();
frame.setContentPane(ContentPane);
ContentPane.setLayout(new BorderLayout(0, 0));
panel = new JPanel()
{
public void paintComponent(Graphics g) {
super.paintComponent(g);
panel.setBackground(new Color(50,160,55));
}
};
glassPane = new MyGlassPane(panel);
frame.setGlassPane(glassPane);
glassPane.setVisible(true);
panel.addMouseListener(new MouseAdapter() {
int[] pos = new int[2];
#Override
public void mouseClicked(MouseEvent e) {
System.out.println("Handles click event");
Graphics g = panel.getGraphics();
g.setColor(new Color(50,165,55));
g.drawLine(pos[0], pos[1], 0+pos[0], 0);//to top
g.drawLine(pos[0], pos[1], 0+pos[0], panel.getHeight());//to bottom
int y = e.getYOnScreen();
int x = e.getXOnScreen();
pos[0]= x;
pos[1] = y;
g.setColor(new Color(0,0,0));
g.drawLine(x, y, 0+x, 0);//to top
g.drawLine(x, y, 0+x, panel.getHeight());//to bottom
g.dispose();
}
});
ContentPane.add(panel, BorderLayout.CENTER);
}
GlassPane Class
import java.awt.AWTException;
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Robot;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.util.ArrayList;
import javax.swing.JComponent;
class MyGlassPane extends JComponent implements ItemListener {
Point point;
protected void paintComponent(Graphics g) {
}
public void setPoint(Point p) {
point = p;
}
public MyGlassPane(final Container contentPane) throws AWTException {
final Component glass = this;
addMouseMotionListener(new MouseMotionListener()
{
ArrayList<Integer> line = new ArrayList<Integer>();
Robot rb = new java.awt.Robot();
#Override
public void mouseMoved(MouseEvent e) {
//System.out.println("Moving");
Graphics g = glass.getGraphics();
if(!line.isEmpty())
{
//System.out.println("line is not empty");
g.setColor(new Color(50,160,55));
g.drawLine(line.get(0), line.get(1), 0+line.get(0), 0);//to top
g.drawLine(line.get(0), line.get(1), 0+line.get(0), contentPane.getHeight());//to bottom
}
//System.out.println("draw line");
int x = e.getXOnScreen();
int y = e.getYOnScreen();
Color col = rb.getPixelColor(x, y);
//System.out.println(col.toString() + " : " + Color.white.toString());
//System.out.println(col.equals(new Color(255,255,255)));
if(!col.equals(new Color(255,255,255)) && !inEndZone(x))
{
g.setColor(new Color(255,0,0));
line = new ArrayList<Integer>();
line.add(x);line.add(y);
g.drawLine(x, y, 0+line.get(0), 0);//to top
g.drawLine(x, y, 0+line.get(0), contentPane.getHeight());//to bottom
}
g.dispose();
}
private boolean inEndZone(int x) {
int ends = contentPane.getWidth()/10;
//System.out.println(x + " : " + ends);
if(x<ends)
{
//System.out.println("In endzone");
return true;
}
else if(x>contentPane.getWidth()-ends)
{
return true;
}
else
{
return false;
}
}
#Override
public void mouseDragged(MouseEvent e) {
// TODO Auto-generated method stub
}
});
addMouseListener(new CBListener(this,contentPane));
}
#Override
public void itemStateChanged(ItemEvent e) {
// TODO Auto-generated method stub
setVisible(e.getStateChange() == ItemEvent.SELECTED);
}
}
Listener Class ( for dispatching the mouse click)
import java.awt.Component;
import java.awt.Container;
import java.awt.Point;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.event.MouseEvent;
import javax.swing.SwingUtilities;
import javax.swing.event.MouseInputAdapter;
class CBListener extends MouseInputAdapter {
Toolkit toolkit;
Robot rb;
MyGlassPane glassPane;
Container contentPane;
public CBListener(MyGlassPane glassPane, Container contentPane) {
toolkit = Toolkit.getDefaultToolkit();
this.glassPane = glassPane;
this.contentPane = contentPane;
}
#Override
public void mouseClicked(MouseEvent e) {
redispatchMouseEvent(e, false);
}
// A basic implementation of redispatching events.
private void redispatchMouseEvent(MouseEvent e, boolean repaint) {
Point glassPanePoint = e.getPoint();
Container container = contentPane;
Point containerPoint = SwingUtilities.convertPoint(glassPane,
glassPanePoint, contentPane);
if (containerPoint.y < 0) { // we're not in the content pane
} else {
// The mouse event is probably over the content pane.
// Find out exactly which component it's over.
Component component = SwingUtilities.getDeepestComponentAt(
container, containerPoint.x, containerPoint.y);
if ((component != null) && (component.equals(contentPane))) {
System.out.println("contentPane");
// Forward events over the check box.
Point componentPoint = SwingUtilities.convertPoint(glassPane,
glassPanePoint, component);
component.dispatchEvent(new MouseEvent(component, e.getID(), e
.getWhen(), e.getModifiers(), componentPoint.x,
componentPoint.y, e.getClickCount(), e
.isPopupTrigger()));
}
}
// Update the glass pane if requested.
if (repaint) {
glassPane.setPoint(glassPanePoint);
glassPane.repaint();
}
}
}

I can get it to redirect the mouseClick to the bottom panel but it
wont draw the line. It just makes the redline disappear until you move
the mouse again
No, It is drawing black line indeed. But the line is drawn above the red line that makes the red line to vanish till the mouse is moved again . I Guess you are looking for something like this:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class DoublePanel extends JFrame
{
JPanel mainPanel;
int x1;
public void prepareAndShowGUI()
{
setTitle("DoublePanel");
mainPanel = new JPanel()
{
#Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(Color.BLACK);
g.drawLine(x1,0,x1,this.getHeight());
}
};
mainPanel.setBackground(new Color(50,160,55));
mainPanel.setLayout(new BorderLayout());
mainPanel.add(new upperPanel(this));
setContentPane(mainPanel);
setSize(500,600);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(false);
setVisible(true);
}
public void setXValue(int x)
{
this.x1 = x;
mainPanel.repaint();
}
class upperPanel extends JPanel
{
int x; int y;
DoublePanel dp;
upperPanel(DoublePanel d)
{
this.dp = d;
setOpaque(false);
addMouseMotionListener(new MouseAdapter()
{
#Override
public void mouseMoved(MouseEvent evt)
{
x = evt.getX();
y = evt.getY();
repaint();
}
});
addMouseListener(new MouseAdapter()
{
#Override
public void mouseClicked(MouseEvent evt)
{
dp.setXValue(evt.getX());
}
});
}
#Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(Color.RED);
g.drawLine(x,0,x,this.getHeight());
}
}
public static void main(String st[])
{
SwingUtilities.invokeLater( new Runnable()
{
public void run()
{
DoublePanel dp = new DoublePanel();
dp.prepareAndShowGUI();
}
});
}
}

You need to call the bottom panel's repaint().