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java jlabel disappears in game loop

The goal here is to use jlabels with an image icon that contains a BufferedImage. Those jlabels can then be easily moved around with the mouse without having to go searching a ton of different BufferedImages on the screen to find out which one is being clicked on.
This is easy to do in a standard JFrame. I've been searching around here for an hour trying to figure out how to implement this in a game loop where a paintComponent is overridden.
import javax.swing.*;
import java.awt.*;
public class Main {
public Main() {
}
public static void main(String[] args) {
JFrame window = new JFrame();
GamePanel gamePanel = new GamePanel();
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setResizable(true);
window.setLayout(new FlowLayout());
window.setTitle("FX Test");
window.add(gamePanel);
window.pack();
window.setLocationRelativeTo(null);
window.setVisible(true);
gamePanel.startGameThread();
}
}
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
public class GamePanel extends JPanel implements ActionListener {
private Timer gameLoopTimer;
public int screenWidthPixels = 640;
public int screenHeightPixels = 480;
private int counter;
private int x = 1;
private float alpha = 1;
private final int DELAY = 15;
private final int INITIAL_DELAY = 200;
public GamePanel() {
this.setPreferredSize(new Dimension(screenWidthPixels, screenHeightPixels));
this.setBackground(Color.black);
this.setDoubleBuffered(true);
this.setFocusable(true);
this.requestFocus();
counter = 0;
JButton testButton = new JButton("Button Test");
this.add(testButton);
JLabel label = new JLabel(new String("Label test"));
label.setVisible(true); // Doesn't seem to be needed.
this.add(label);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.WHITE);
g2.drawString("Game Panel Testing: " + counter,128,129);
g2.dispose();
}
#Override
public void actionPerformed(ActionEvent e) {
repaint();
update();
}
void startGameThread() {
gameLoopTimer = new Timer(DELAY,this);
gameLoopTimer.setInitialDelay(INITIAL_DELAY);
gameLoopTimer.start();
}
}
That code draws "Game Panel Testing: " and the incrementing counter, but no button and no label.
If I comment out the entire paintComponent I'm overriding, the button and label appear as expected.
What I can't wrap my head around is how to get the label and button to appear again once paintComponent is overridden. I thought the super.paintComponent(g) would take care of that automatically, but clearly I'm missing something here. How on earth can I add a bunch of JLabels to this game loop instead of having to manually handle moving of g2 drawn BufferedImages on mouse drag?

The jlabels are not drawn since you have overridden the paintComponent method.
The call to super is on the super class, so you have misunderstood how that call works.
If you put your in a class that inherits from your class with jlabels it will work.

Wrong RGB values are returned

I am trying to get the RGB value of a pixel of an image. (The pixel that the mouse is over). Here is the code which adds the image and the code which attends to the mouse ::
/// I got this code somewhere from StackOverFlow;
///Couldn't find the link;
label = new JLabel();
try {
// THIS PICTURE IS NOT MINE
targetImg = ImageIO.read(new java.net.URL("https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSFAhy8GM1F3_TyPjG7ezbeFRUy00PN4hpJCA&usqp=CAU"));
label.setIcon(new ImageIcon(rescale(targetImg)));
panel1.add(label);
fields = new JPanel();
fields.setBorder(new EmptyBorder(5, 5, 5, 5));
red = new JTextField(3);
green = new JTextField(3);
blue = new JTextField(3);
red.setEditable(false);
green.setEditable(false);
blue.setEditable(false);
fields.add(red);
fields.add(green);
fields.add(blue);
panel1.add(fields);
label.addMouseMotionListener(new MouseAdapter() {
#Override
public void mouseMoved(MouseEvent e) {
try{
int packedInt = targetImg.getRGB(e.getX(), e.getY());
Color color = new Color(packedInt, true);
fields.setBackground(color);
red.setText(Integer.toString(color.getRed()));
green.setText(Integer.toString(color.getGreen()));
blue.setText(Integer.toString(color.getBlue()));
}
catch (ArrayIndexOutOfBoundsException exception) { }
}
});
} catch (IOException ex) {
ex.printStackTrace();
}
This runs and compiles fine; However, sometimes the color returned by the RGB is not the color my mouse is on; Here is a pic ::
https://i.stack.imgur.com/R5qIx.png
Note: The white cross is an approximate location of where it is; A screenshot apparently does not take the mouse too.
The code is also laggy. Sometimes it hangs on one pixel and I have to wait until it runs again.
Why does this happen, and what can I do to prevent this? How can I solve this problem?

Since you only provided a code snippet, I created the following GUI.
Since the picture was so small, I put it under the RGB display.
The main problem was matching coordinate systems so that the mouse pointer would point to the pixel in the image. When you put the image inside a JLabel, you have to translate the mouse coordinate to an image coordinate.
I sidestepped the coordinate system problem by creating a drawing JPanel. By drawing the image on a drawing JPanel and adding the MouseMotionListener to the drawing JPanel, the mouse coordinates match the image coordinates.
I started the Swing application with a call to the SwingUtilities invokeLater method. This method ensures that the Swing components are created and executed on the Event Dispatch Thread.
I created a JFrame, an RGB JPanel, and a drawing JPanel. The JFrame methods must be executed in a specific order. This is the order I use for all my Swing applications.
The RGB JPanel uses a FlowLayout to separate the red, green, and blue JTextFields.
The drawing JPanel draws the image. The drawing JPanel is the same size as the image. Again, by drawing the image on a drawing JPanel and adding the MouseMotionListener to the drawing JPanel, the mouse coordinates match the image coordinates.
I made the ColorListener a separate class. I basically copied your code to the mouseMoved method.
Here's the complete runnable code. I made the classes inner classes so I could paste this code as one block.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class RGBProcessor implements Runnable {
public static void main(String[] args) {
SwingUtilities.invokeLater(new RGBProcessor());
}
private BufferedImage image;
private Color panelColor;
private DrawingPanel drawingPanel;
private JPanel rgbPanel;
private JTextField redField;
private JTextField greenField;
private JTextField blueField;
public RGBProcessor() {
this.panelColor = Color.RED;
this.image = getImage();
this.drawingPanel = new DrawingPanel(this, image);
this.rgbPanel = createRGBPanel();
}
#Override
public void run() {
JFrame frame = new JFrame("RGB Processor");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(rgbPanel, BorderLayout.BEFORE_FIRST_LINE);
frame.add(drawingPanel, BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createRGBPanel() {
JPanel panel = new JPanel();
panel.setBackground(panelColor);
panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
redField = new JTextField(4);
redField.setEditable(false);
panel.add(redField);
greenField = new JTextField(4);
greenField.setEditable(false);
panel.add(greenField);
blueField = new JTextField(4);
blueField.setEditable(false);
panel.add(blueField);
return panel;
}
private BufferedImage getImage() {
try {
return ImageIO.read(new URL("https://encrypted-tbn0.gstatic.com/"
+ "images?q=tbn:ANd9GcSFAhy8GM1F3_TyPjG7ezbe"
+ "FRUy00PN4hpJCA&usqp=CAU"));
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
public void setPanelColor(Color color) {
this.panelColor = color;
this.rgbPanel.setBackground(color);
}
public JTextField getRedField() {
return redField;
}
public JTextField getGreenField() {
return greenField;
}
public JTextField getBlueField() {
return blueField;
}
public class DrawingPanel extends JPanel {
private static final long serialVersionUID = 1L;
private BufferedImage image;
public DrawingPanel(RGBProcessor frame, BufferedImage image) {
this.image = image;
this.setPreferredSize(new Dimension(image.getWidth(),
image.getHeight()));
this.addMouseMotionListener(new ColorListener(frame, image));
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(image, 0, 0, this);
}
}
public class ColorListener extends MouseAdapter {
private RGBProcessor frame;
private BufferedImage image;
public ColorListener(RGBProcessor frame, BufferedImage image) {
this.frame = frame;
this.image = image;
}
#Override
public void mouseMoved(MouseEvent event) {
int packedInt = image.getRGB(event.getX(), event.getY());
Color color = new Color(packedInt, true);
frame.setPanelColor(color);
frame.getRedField().setText(Integer.toString(color.getRed()));
frame.getGreenField().setText(Integer.toString(color.getGreen()));
frame.getBlueField().setText(Integer.toString(color.getBlue()));
}
}
}

JFrame (Swing) update(graphics) error

I have a little game with little Rect, which are moving and I need to update the Graphics by doing this.update(MyGraphics) in my onUpdate method, which gets called every 50 millisekonds. But when I do this this.update(MyGraphics) all my buttons and textfields are glitched.
Does somebody have an idea how to fix it?

when I do this this.update(MyGraphics) all my buttons and textfields are glitched.
Don't invoke update(...) directly. That is not the way custom painting is done.
Instead when you do custom painting you override the paintComponent(...) method of the JPanel:
#Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
// add your custom painting here
}
I have a little game with little Rect, which are moving
If you want animation then you should use a Swing Timer to schedule the animation. Then when the Timer fires you invoke a method on your custom class to change the location of the rectangle and then you invoke repaint(). This will cause the panel to be repainted.
Read the Swing Tutorial. There are sections on:
Performing Custom Painting
How to Use Swing Timers
to get your started with basic examples.

Here is one of the examples how to update JPanel by a timer.
import java.awt.Color;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
public class MainClass extends JPanel {
static JFrame frame = new JFrame("Oval Sample");
static MainClass panel = new MainClass(Color.CYAN);
static Color colors[] = {Color.RED, Color.BLUE, Color.GREEN, Color.YELLOW};
static Color color;
static int step = 0;
public MainClass(Color color) {
this.color = color;
}
final static Timer tiempo = new Timer(500, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// paintComponent();
System.out.println("Step: " + step++);
if (step % 2 == 0) {
color = Color.DARK_GRAY;
} else {
color = Color.BLUE;
}
panel.repaint();
}
});
#Override
public void paintComponent(Graphics g) {
int width = getWidth();
int height = getHeight();
g.setColor(color);
g.drawOval(0, 0, width, height);
}
public static void main(String args[]) {
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new GridLayout(2, 2));
panel = new MainClass(colors[2]);
frame.add(panel);
frame.setSize(300, 200);
frame.setVisible(true);
tiempo.start();
}
}

How to prevent the JPanel from being updated?

I'm creating a sort of paint application. The user can move a circle in a JPanel by pressing/dragging the mouse.
I have a JCheckBoxMenuItem in one of my JMenus:
JCheckBoxMenuItem checkitem = new JCheckBoxMenuItem("Draw mode",false);
When it is not activated, the circle can only be moved (by dragging/pressing) and the previous circle will be erased.
When it is activated, the circle can only be moved, but the previous circle will not be erased when dragging/pressing the mouse ( This works the same way as a paint program )
Shortened version of my code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class GUI extends JFrame implements MouseListener, MouseMotionListener, ActionListener, ItemListener
{
JPanel mainPan, colorPan;
Color color = Color.BLACK;
JCheckBoxMenuItem checkitem;
boolean clear = true;
public GUI(String header)
{
maker();
mainPan.addMouseListener(this);
mainPan.addMouseMotionListener(this);
add(mainPan , BorderLayout.CENTER);
add(colorPan, BorderLayout.PAGE_END);
}
public void maker()
{
colorPan = new JPanel();
colorPan.setLayout(new GridLayout(1, 0));
mainPan = new JPanel(){
#Override
public void paintComponent(Graphics g)
{
//g.setColor(Color.WHITE);
//g.fillRect(0,0,getWidth(),getHeight());
if(clear)
super.paintComponent(g); //Do the same thing as above(Clear JPanel)
g.setColor(color);
g.fillOval(x,y,50,50); //x and y are integer variables that I use in my full program
}
};
checkitem = new JCheckBoxMenuItem("Draw mode",false);
//After adding this to a JMenu,
checkitem.addItemListener(this);
}
public void itemStateChanged(ItemEvent e)
{
if(e.getStateChange() == ItemEvent.SELECTED)
{
clear = false;
}
else
{
clear = true;
}
}
}
The below screenshot shows the output of my full program:
colorPan is the JPanel full of JButtons of different colors. The top of it is mainPan.
Right now, the "Draw mode" doesn't work as expected. I had always thought that super.paintComponent(g); was the one that clears/resets the screen when repaint() is called. But I removed that and was quite surprised to see the program behave the same way.
Basically, my problem is here:
if(clear)
super.paintComponent(g);
I need to prevent everything from being cleared when repaint() is called. How do I achieve what I want?

It is not in this code where changes should be made. And it is not paint method which should be changed. Paint paints whenever is required either by your or by system. When window is resized or moved or partially covered - it uses paint to paint picture again.
What you should really do is to stop updating coordinates for your painted oval. It could be done in mouse listener or in coordinates setter or, better, in control part which manages these coordinates. Your checkbox should control ability to change your model. It should not control painting.
There is commonly used pattern Model-View-Controller - look at it. Maybe it could look like overkill for such small application but even Swing itself is built on this pattern so you already follow it. Issues rise when you try to break it. So - don't.

You can't "prevent the JPanel from being updated;" paintComponent() will be called asynchronously, as required by the system. Instead, condition attributes of your view class in a way that allows your implementation of paintComponent() to render everything whenever it is called.
In the example below, the foreground color is changed with each mouse click and paintComponent() uses the revised setting. In the more elaborate example cited here, ClearAction clears the List<Node> and List<Edge> that define the graph's model. Absent a call to super.paintComponent(g), otherwise required for an opaque component, a call to fillRect() in paintComponent() cleans up any leftover selection artifacts.
public void actionPerformed(ActionEvent e) {
nodes.clear();
edges.clear();
repaint();
}
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
/** #see https://stackoverflow.com/a/5312702/230513 */
public class MouseDragTest extends JPanel {
private static final String TITLE = "Drag me!";
private static final Random r = new Random();
private static final int W = 640;
private static final int H = 480;
private Point textPt = new Point(W / 2, H / 2);
private Point mousePt;
private Color color = Color.black;
public MouseDragTest() {
this.setFont(new Font("Serif", Font.ITALIC + Font.BOLD, 32));
this.addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
mousePt = e.getPoint();
setColor(Color.getHSBColor(r.nextFloat(), 1, 1));
repaint();
}
});
this.addMouseMotionListener(new MouseMotionAdapter() {
#Override
public void mouseDragged(MouseEvent e) {
int dx = e.getX() - mousePt.x;
int dy = e.getY() - mousePt.y;
textPt.setLocation(textPt.x + dx, textPt.y + dy);
mousePt = e.getPoint();
repaint();
}
});
}
public void setColor(Color color) {
this.color = color;
}
#Override
public Dimension getPreferredSize() {
return new Dimension(W, H);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(color);
int w2 = g.getFontMetrics().stringWidth(TITLE) / 2;
g.drawString(TITLE, textPt.x - w2, textPt.y);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JFrame f = new JFrame(TITLE);
f.add(new MouseDragTest());
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
});
}
}

JPanel Animated Background

This is a really general question, but how should I add an animated background for a JPanel. I want the background to be behind all the panel's components and graphics. Right now, I have two separate classes (one for the main panel and the other for the background). The background class uses repaint() to animate a grid moving across the screen. I've tried to make the main panel background transparent, but that hasn't gotten me anywhere.
Even more info:
My main panel is part of a CardLayout and it has many different classes in it. So when I'm adding my main panel to my main frame, I'm doing frame.getContentPane().add(cards, BorderLayout.CENTER)
cards is a JPanel which acts as a container for the mainpanel and all the panels inside main panel.
Can anybody help me out in getting a panel animated background?

You can use Toolkit.getImage() to load animated image and then draw the image in container's paintComponent. Make sure the ImageObserver is set (not null) in order to update animation frames properly. For details how image is loaded, observed and updated see How Images are Loaded appendix in Java AWT Reference.
Here is a simple example:
import java.awt.*;
import javax.swing.*;
import java.net.URL;
class AnimatedPanelDemo {
static class ImagePanel extends JPanel {
private Image image;
ImagePanel(Image image) {
this.image = image;
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(image,0,0,getWidth(),getHeight(),this);
}
}
private static void createAndShowUI() {
try {
JFrame frame = new JFrame("Image");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
Image image = Toolkit.getDefaultToolkit().getImage(new URL(
"http://duke.kenai.com/iconSized/duke.running.gif"));
ImagePanel imagePanel = new ImagePanel(image);
imagePanel.add(new JLabel("Some label"));
frame.add(imagePanel);
frame.setSize(100, 100);
frame.setVisible(true);
}
catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowUI();
}
});
}
}

Well, this is my first answer on stackoverflow.
Will try to help with my learning curve with this complex AWT and Swift API.
Below there's the contructor that extends JFrame
package xpto;
import java.awt.Dimension;
import java.awt.GraphicsConfiguration;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.awt.event.WindowStateListener;
import java.awt.image.ImageObserver;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import sun.java2d.SunGraphicsEnvironment;
import java.awt.Graphics;
import java.awt.Graphics2D;
public class FrameLuckyRaffle extends JFrame {
/**
*
*/
private JLabel backgroundLabel;
private ImageIcon imageIcon;
private Image bgImage;
/**
* Constructor of this frame.
*/
public FrameLuckyRaffle(String background, final String dbname) {
try {
setTitle("Lucky Raffle of "+ dbname);
GraphicsConfiguration config = this.getGraphicsConfiguration();
Rectangle usableBounds = SunGraphicsEnvironment.
getUsableBounds(config.getDevice());
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
setBounds(100, 100, (int)(usableBounds.getWidth()*0.8),
(int)(usableBounds.getHeight()*0.8));
setMinimumSize(new Dimension(1024, 700));
setResizable(true);
setDefaultLookAndFeelDecorated(true);
backgroundLabel = new JLabel() {
public void paintComponent(Graphics g) {
// alternative --> g.drawImage(bgImage, 0, 0, null);
// I prefer to control the new ImageObserver parameter as bellow
g.drawImage(bgImage, 0, 0, new ImageObserver() {
#Override
public boolean imageUpdate(Image img, int infoflags,
int x, int y, int width, int height) {
img.getScaledInstance(getWidth(),getHeight(),
Image.SCALE_FAST);
return true;
}
});
// this is used to have easier control on
// image manipulation on my application
Graphics2D g2d = (Graphics2D)g;
super.paintComponent(g2d);
revalidate();
repaint();
}
};
backgroundLabel.setBounds(0, 0, 0, 0);
// this is necessary if you want more child
// components to be visible on the JFrame afterwards
backgroundLabel.setOpaque(false);
setContentPane(backgroundLabel);
addWindowListener(new WindowListener() {
#Override
public void windowOpened(WindowEvent e) {
// Set Frame Background
imageIcon = new ImageIcon(Toolkit.getDefaultToolkit().
createImage(FrameBusinessPure.class.getResource(background)));
bgImage = imageIcon.getImage().
getScaledInstance(getWidth(),getHeight(), Image.SCALE_FAST);
}
// Even after closing the window, JVM didn't Garbage Collected the instanced
// objects, for some reason. Forcing the objects to null helped on that.
#Override
public void windowClosed(WindowEvent e) {
backgroundLabel = null;
imageIcon = null;
bgImage = null;
System.gc();
}
});
addWindowStateListener(new WindowStateListener() {
#Override
public void windowStateChanged(WindowEvent e) {
// if you flush the object on runtime you will surpass the
// memory leak on using GIFs and most complex graphics
bgImage.flush();
bgImage = imageIcon.getImage().
getScaledInstance(getWidth(),getHeight(), Image.SCALE_FAST);
}
});
addMouseMotionListener(new MouseMotionListener() {
#Override
public void mouseDragged(MouseEvent e) {
// if you flush the object on runtime you will surpass the
// memory leak on using GIFs and most complex graphics
bgImage.flush();
bgImage = imageIcon.getImage().
getScaledInstance(getWidth(),getHeight(), Image.SCALE_FAST);
});
}catch (Exception e) {
e.printStackTrace();
}
}
}
Feel free to learn more on below link
https://www.oracle.com/java/technologies/painting.html