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Java Drawing to a JPanel (debugging)

I'm trying to draw a basic object to a JPanel
although it doesn't seem to be working.
I'm certain I am doing something wrong with where the paint method
is being called
import javax.swing.*;
import java.awt.*;
import java.awt.image.*;
public class testGui {
static colors gc_colors;
static gui gc_gui;
public static void main(String[] args) {
gc_colors = new colors();
gc_gui = new gui();
gc_gui.cv_frame.setVisible(true);
}
public static class colors {
Color cv_ltGrey;
Color cv_mdGrey;
Color cv_dkGrey;
public colors() {
cv_ltGrey = Color.decode("#DDDDDD");
cv_mdGrey = Color.decode("#CCCCCC");
cv_dkGrey = Color.decode("#111111");
}
}
public static class gui {
JFrame cv_frame;
JPanel cv_panel;
JPanel 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_panel = new JPanel();
cv_panel.setBackground(gc_colors.cv_ltGrey);
cv_panel.setPreferredSize(new Dimension(500, 300));
cv_frame.add(cv_panel);
cv_content = new content();
cv_panel.add(cv_content);
}
}
public static class content extends JPanel {
public void paint(Graphics graphic) {
super.paint(graphic);
draw(graphic);
}
public void update() {
repaint();
}
public void draw(Graphics graphic) {
Graphics2D graphic2D = (Graphics2D) graphic;
graphic2D.setPaint(gc_colors.cv_ltGrey);
graphic2D.fillRect(10, 10, 100, 100);
}
}
}
I have a class for my gui which I am adding a JPanel to (a light grey one).
Which I am then trying to add my drawing to using a JPanel extended class
called content.
When I run it though it seems to create the grey JPanel which I want but
the drawing is just a tiny white square and I'm not sure why.

So, you content panel has a default preferred size of 0x0, FlowLayout honours the preferredSize of its components (with a little margin), hence the reason why you have a nice little small white rectangle.
What you need to do is override the getPreferredSize method of the content panel and return a suitable size, for example
public static class content extends JPanel {
#Override
public Dimension getPreferredSize() {
return new Dimension(120, 120);
}
public void paint(Graphics graphic) {
super.paint(graphic);
draw(graphic);
}
public void update() {
repaint();
}
public void draw(Graphics graphic) {
Graphics2D graphic2D = (Graphics2D) graphic;
graphic2D.setPaint(gc_colors.cv_ltGrey);
graphic2D.fillRect(10, 10, 100, 100);
}
}

I've decided to just leave out the second JPanel altogether.
It was too much of a hassle to put the JPanel inside of another JPanel
so instead I am only going to use a single JPanel
public static class gui {
JFrame cv_frame;
JPanel cv_panel;
JPanel 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_content = new content();
cv_content.setBackground(gc_colors.cv_ltGrey);
cv_content.setPreferredSize(new Dimension(500, 300));
cv_frame.add(cv_content);
}
}

Drawing Captured Screen Image in JPanel ,Image is displayed one more time ?How can I fix it to be display one timw?

I Want to capture Image from screen and draw it in JPanel , it works but it is displayed one more time like entering in a loop , I am confused by this , How can I fix it ,Please?
Varibles Iwidth,Ihieght ares above initiaized, but I take the block of code that cause the problem
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Image img;
ImageIcon i = null;
Rectangle screenRect=new Rectangle(Toolkit.getDefaultToolkit().getScreenSize());
try {
BufferedImage capture=new Robot().createScreenCapture(screenRect);
capture.getHeight();
capture.getWidth();
i=new ImageIcon(capture);
} catch (AWTException ex) {
Logger.getLogger(TestDrawing.class.getName()).log(Level.SEVERE, null, ex);
}
img = i.getImage();
g.drawImage(img,Iwidth,Ihieght,null);
super.repaint();
}

Never have code like that inside of paintComponent. That method should be reserved for painting and painting only, and is a method that you don't really have full control over since it is called by the JVM in response to both your request, and to requests from the OS, and even if you request a repaint, there's no guarantee that it will be complied with, especially if the requests are stacking up. Also, your GUI's perceived responsiveness will often depend on how quick painting is done, which is while file reading and image capturing should never be done inside of paintComponent.
Instead, you should read the image in as a reaction to some event, perhaps a Timer, then after the image is read, call repaint() and in paintComponent draw the obtained image.
Never call repaint() inside of paintComponent either.
Something like in pseudo code
// inside of the ActionListener of a Swing Timer (if you want to do this repeatedly)
get screen image from robot and feed it into the capture BufferedImage field
consider doing this in a SwingWorker
call repaint() when SwingWorker is done (via a PropertyChangeListener)
Inside of paintComponent:
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (capture != null) {
g.drawImage(capture, capture.getWidth(), capture.getHeight());
}
}
Edit
For example:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.concurrent.ExecutionException;
import javax.swing.*;
import javax.swing.SwingWorker.StateValue;
public class ScreenCaptureTest extends JPanel {
private static final int PREF_W = 600;
private static final int PREF_H = 400;
private JButton btn = new JButton(new ScreenCaptureAction(this,
"Capture Screen", KeyEvent.VK_C));
private ImagePanel imagePanel = new ImagePanel();
public ScreenCaptureTest() {
JPanel buttonPanel = new JPanel();
buttonPanel.add(btn);
setLayout(new BorderLayout());
add(new JScrollPane(imagePanel), BorderLayout.CENTER);
add(buttonPanel, BorderLayout.SOUTH);
}
public void setImagePanelImage(BufferedImage img) {
imagePanel.setImage(img);
revalidate();
repaint();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
private static void createAndShowGui() {
ScreenCaptureTest mainPanel = new ScreenCaptureTest();
JFrame frame = new JFrame("ScreenCaptureTest");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
class ImagePanel extends JPanel {
private BufferedImage image;
public void setImage(BufferedImage image) {
this.image = image;
revalidate();
repaint();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (image != null) {
g.drawImage(image, 0, 0, null);
}
}
#Override
public Dimension getPreferredSize() {
if (image != null) {
return new Dimension(image.getWidth(), image.getHeight());
}
return super.getPreferredSize();
}
}
class ScreenCaptureAction extends AbstractAction {
private ScreenCaptureTest screenCaptureTest;
public ScreenCaptureAction(ScreenCaptureTest screenCaptureTest, String name,
int mnemonic) {
super(name);
putValue(MNEMONIC_KEY, mnemonic);
this.screenCaptureTest = screenCaptureTest;
}
#Override
public void actionPerformed(ActionEvent e) {
setEnabled(false);
final SwingWorker<BufferedImage, Void> mySwingWorker = new SwingWorker<BufferedImage, Void>() {
#Override
protected BufferedImage doInBackground() throws Exception {
Toolkit toolkit = Toolkit.getDefaultToolkit();
Dimension screenSize = toolkit.getScreenSize();
Robot robot = new Robot();
BufferedImage capture = robot.createScreenCapture(new Rectangle(
screenSize));
return capture;
}
};
mySwingWorker.addPropertyChangeListener(new PropertyChangeListener() {
#Override
public void propertyChange(PropertyChangeEvent pcEvt) {
if ("state".equals(pcEvt.getPropertyName())
&& pcEvt.getNewValue() == StateValue.DONE) {
setEnabled(true);
try {
screenCaptureTest.setImagePanelImage(mySwingWorker.get());
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
}
}
});
mySwingWorker.execute();
}
}
Edit
Note, that if this were my program, I'd display the image as an ImageIcon in a JLabel as it is much simpler to code. Then you could do away with the ImagePanel class and its paintComponent method, and simply code the main as:
public class ScreenCaptureTest extends JPanel {
private static final int PREF_W = 600;
private static final int PREF_H = 400;
private JButton btn = new JButton(new ScreenCaptureAction(this,
"Capture Screen", KeyEvent.VK_C));
//!! private ImagePanel imagePanel = new ImagePanel();
private JLabel screenLabel = new JLabel(); //!!
public ScreenCaptureTest() {
JPanel buttonPanel = new JPanel();
buttonPanel.add(btn);
setLayout(new BorderLayout());
//!! add(new JScrollPane(imagePanel), BorderLayout.CENTER);
add(new JScrollPane(screenLabel), BorderLayout.CENTER); //!!
add(buttonPanel, BorderLayout.SOUTH);
}
public void setImagePanelImage(BufferedImage img) {
//!! imagePanel.setImage(img);
Icon icon = new ImageIcon(img);
screenLabel.setIcon(icon);
//!! revalidate();
//!! repaint();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
private static void createAndShowGui() {
ScreenCaptureTest mainPanel = new ScreenCaptureTest();
JFrame frame = new JFrame("ScreenCaptureTest");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

CardLayout with MouseListener not working

I am dealing with CardLayout. The JPanel I added as a contentpane to my JFrame has a CardLayout, and I want to swap between different panes. I have a working pane with buttons and five other image panes for the tutorial that are to be displayed only if a certain boolean value is true. I mean, every time this boolean is set true, five swaps should be done using next() method. My problem is that, after the first swap, the screen becomes blank. why does this happen?
Second question. I am using a MouseListener to swap, but I would like the program to do it automatically after some time. I tried to use Thread.sleep(5000), but I get a black screen.
This is my code, where card is a class variable in order to use it in the Mouselistener, parent is the working panel, already created, and ImagePanel is a class to create tutorialPanels, which adds to them the MouseListener below. Also, rootPane is a class pane.
card = new CardLayout();
rootPane = new JPanel(card);
this.getContentPane().add(rootPane);
//create panels to add
ImagePanel inputTutorial = new ImagePanel("backgroundIn.png");
ImagePanel numericTutorial = new ImagePanel("backgroundNum");
ImagePanel outputTutorial = new ImagePanel("backgroundOut");
ImagePanel commandTutorial = new ImagePanel("backgroundCom");
ImagePanel errorTutorial = new ImagePanel("backgroundErr");
ImagePanel finalTutorial = new ImagePanel("backgroundFinal");
//add the panels
rootPane.add(parent);
rootPane.add(inputTutorial);
rootPane.add(numericTutorial);
rootPane.add(outputTutorial);
rootPane.add(commandTutorial);
rootPane.add(errorTutorial);
rootPane.add(finalTutorial);
//set rootPane content panel
this.getContentPane().add(rootPane);
//if the boolean is true
if (firstTime == true) {
card.next(rootPane);
//other swaps done by mouselisteners
}
This is the mouselistener:
//mouse click listener
private class MouseActionListener implements MouseListener {
public void mousePressed (MouseEvent e) {
}
#Override
public void mouseClicked(MouseEvent arg0) {
card.next(rootPane);
}
#Override
public void mouseEntered(MouseEvent arg0) {
}
#Override
public void mouseExited(MouseEvent arg0) {
}
#Override
public void mouseReleased(MouseEvent arg0) {
}
}
I know that the listener is executed because I checked it.
Any help would be appreciated, thank you in advance.

"but I would like the program to do it automatically after some time. I tried to use Thread.sleep(5000)"
Don't use Thread.sleep. Instead use a javax.swing.Timer. You can learn more at How to Use Swing Timers
Here's a simple example, using some of your app format.
import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class SlideShow {
public SlideShow() {
final CardLayout layout = new CardLayout();
final JPanel mainPanel = createMainPanel(layout);
Timer timer = new Timer(1000, new ActionListener(){
public void actionPerformed(ActionEvent e) {
layout.next(mainPanel);
}
});
timer.start();
JFrame frame = new JFrame();
frame.add(mainPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
private JPanel createMainPanel(CardLayout layout) {
JPanel panel = new JPanel(layout);
panel.add(new ImagePanel("mario.png"));
panel.add(new ImagePanel("bowser.png"));
panel.add(new ImagePanel("luigi.png"));
panel.add(new ImagePanel("koopa.png"));
panel.add(new ImagePanel("princess.png"));
return panel;
}
private class ImagePanel extends JPanel {
BufferedImage image;
public ImagePanel(String fileName) {
try {
image = ImageIO.read(getClass().getResource("/marioblobs/" + fileName));
} catch (IOException ex) {
ex.printStackTrace();
}
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(image, 0, 0, this);
}
#Override
public Dimension getPreferredSize() {
return image == null ? new Dimension(200, 200)
: new Dimension(image.getWidth(), image.getHeight());
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new SlideShow();
}
});
}
}

How to draw PNG Image onto JPanel?

I'm trying to draw a image onto a JPanel by overriding the paintComponent method. However, I'm having no luck with it at all and I don't know why.
Here's the code I've got at the moment:
DrawPanel
public class DrawPanel extends JPanel{
private Image backgroundImg;
public DrawPanel()
{
backgroundImg = Toolkit.getDefaultToolkit().createImage("C:\\Users\\Administrator\\workspace\\Scrub\\src\\loginBackground.png");
}
#Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.drawImage(backgroundImg, 0, 0, null);
}
}
LoginWindow Class
import java.awt.*;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class LoginWindow extends Window{
private DrawPanel panel;
public LoginWindow(int width, int height)
{
super("", width, height);
panel = new DrawPanel();
this.add(panel);
panel.setVisible(true);
}
}
Main
public class Main
{
public static void main(String[] args)
{
LoginWindow loginWindow = new LoginWindow(500, 300);
}
}

There are lots of reasons this might not work
The image might not be getting loaded. You should use ImageIO.read instead, as it will throw an IOException if something goes wrong
The layout manager is using the preferred size of your panel, which is defaulted to 0x0, making the component effectively invisible
You're not setting the window to be visible...
For example
public class DrawPanel extends JPanel{
//...
public Dimension getPreferredSize() {
return backgroundImg == null ? new Dimesion(100, 100) : new Dimension(backgroundImg.getWidth(this), backgroundImg.gtHeight(this));
}
And then in your Window class...
public LoginWindow(int width, int height)
{
super("", width, height);
panel = new DrawPanel();
this.add(panel);
// Swing components are visible by default
//panel.setVisible(true);
// windows aren't
setVisible(true);
}
A simpler soliton would be to use a JLabel...
setLayout(new BorderLayout());
BufferedImage img = ImageIO.read(new File(...));
JLabel label = new JLabel(new ImageIcon(img));
add(label);
setVisible(true);
Take a look at How to use Labels and Reading/Loading an Image for more details

Background image in java swing issue

I've made a Jpanel with a background image and a Jbutton also with its background. The problem is that background sometimes is loaded sometimes no.
public class Window extends JFrame {
public static JFrame createwindow() {//fare singleton
JFrame frame = new JFrame("Battaglia navale");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(740, 740);
frame.setVisible(true);
frame.setResizable( false );
Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
frame.setLocation(((int)dim.getWidth()-(int)frame.getWidth())/2, ((int)dim.getHeight()-(int)frame.getHeight())/2);
return frame;
}
}
public class StartWindow {
JFrame frame;
private JButton button;
private JButton button2;
final String button_start = "img/start.png";
ImageIcon start = new ImageIcon(button_start);
public void CreateStartWindow() {
frame = Window.createwindow();
Container container = frame.getContentPane();
JpanelStart panel = new JpanelStart();
container.add(panel);
this.button = new JButton(start);
button.setActionCommand("start");
button.setHideActionText(true);
button.setOpaque(false);
button.setFocusPainted(false);
button.setBorderPainted(false);
button.setContentAreaFilled(false);
this.button2 = new JButton("Classifica");
panel.add(button);
panel.add(button2);
frame.setVisible(true);
}
public void addActionListener(ActionListener al) {
this.button.addActionListener(al);
this.button2.addActionListener(al);
}
public void chiudi() {
frame.dispose();
}
}
class JpanelStart extends JPanel {
private Image img;
private String path_img = "img/sfondo.jpg";
public JpanelStart() {
img = Toolkit.getDefaultToolkit().createImage(path_img);
loadImage(img);
}
private void loadImage(Image img) {
try {
MediaTracker track = new MediaTracker(this);
track.addImage(img, 0);
track.waitForID(0);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
#Override
protected void paintComponent(Graphics g) {
setOpaque(false);
g.drawImage(img, 0, 0, this);
super.paintComponent(g);
}
}

super.paintComponet should go right after the method signature.
you set the button opacity to false, so it won't be seen.
Run your program from the Event Dispatch Thread.
public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable(){
public void run() {
new StartWindow().CreateStartWindow();
}
});
}
In your method, you're making the frame visible before adding anything. Leave that out in the method
Don't set the size of the frame. Instead override the getPrefereedSize() of the JPanel and call pack() on the frame.
IMO, I see no use at all for this so-called helper method. I would toss it out the window
You should load your image as an embedded resource, and not from the file system.
img = ImageIO.read(StartWindow.class.getResource(path_img));
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.MediaTracker;
import java.awt.Toolkit;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class StartWindow {
JFrame frame;
private JButton button;
private JButton button2;
final String button_start = "img/start.png";
ImageIcon start = new ImageIcon(button_start);
public void CreateStartWindow() throws IOException {
frame = Window.createwindow();
Container container = frame.getContentPane();
JpanelStart panel = new JpanelStart();
container.add(panel);
this.button = new JButton(start);
button.setActionCommand("start");
button.setHideActionText(true);
button.setOpaque(false);
button.setFocusPainted(false);
button.setBorderPainted(false);
button.setContentAreaFilled(false);
this.button2 = new JButton("Classifica");
panel.add(button);
panel.add(button2);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable(){
public void run() {
try {
new StartWindow().CreateStartWindow();
} catch (IOException ex) {
Logger.getLogger(StartWindow.class.getName()).log(Level.SEVERE, null, ex);
}
}
});
}
public void addActionListener(ActionListener al) {
this.button.addActionListener(al);
this.button2.addActionListener(al);
}
public void chiudi() {
frame.dispose();
}
}
class Window {
public static JFrame createwindow() {//fare singleton
JFrame frame = new JFrame("Battaglia navale");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(false);
Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
return frame;
}
}
class JpanelStart extends JPanel {
private static final int D_W = 700;
private static final int D_H = 700;
private Image img;
private String path_img = "/images/logo.gif";
public JpanelStart() throws IOException {
img = ImageIO.read(StartWindow.class.getResource(path_img));
loadImage(img);
}
private void loadImage(Image img) {
try {
MediaTracker track = new MediaTracker(this);
track.addImage(img, 0);
track.waitForID(0);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(img, 0, 0, D_W, D_W, this);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(D_W, D_H);
}
}
**Shows Up Every time **

draw the image after super.paintComponent(g) (which draws the component that you want to draw on top of)
call repaint() in loadImage() after the image is set (so that it redraws it)
loadImage() doesn't seem to be setting the img variable does it need to?
(not essential but recommended) you should also move UI changes into the EDT (Event Dispatch Thread).
Example of running a UI task on EDT
This puts UI operations on a queue so that all UI changes are made from the same thread and avoid interference.
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
//UI Operations
}
} );