Develop Reference

Can't add JLabel to JPanel

I have this code:
ImageIcon ii = new ImageIcon("https://c1.staticflickr.com/9/8384/8682624224_4e44bf947d_h.jpg");
subStream.add(new JLabel(ii));
It's meant to add JLabel with photo to JPanel called subStream.
But it doesn't work, no errors or anything. Why so?
Image is supposed to appear in 3rd JPanel, just above Buttons.

Things to be aware of...
ImageIcon can fail silently...annoying I know...this is because...
ImageIcon uses a background thread to load the images, this is because it was designed to allow for slow sources (dial up networks) which might need time to fully realise the image.
You should use ImageIO.read to test the URL to discount potential issues with downloading the image. This will throw an IOException if the image can't be loaded for some reason and will block until the image is fully loaded, so beware of that
See Reading/Loading an Image for more details
For example...
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.HeadlessException;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
try {
BufferedImage img = ImageIO.read(new URL("https://c1.staticflickr.com/9/8384/8682624224_4e44bf947d_h.jpg"));
JLabel label = new JLabel(new ImageIcon(img));
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(label);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
} catch (IOException exp) {
exp.printStackTrace();
}
}
});
}
}
So, this discounts the image and web server as the potential problem (at least from within my network), there must be something else wrong with your code. Consider providing a runnable example which demonstrates your problem. This will result in less confusion and better responses

You are invoking ImageIcon(String filename) constructor. Try with the URL one:
ImageIcon icon = new ImageIcon(new URL("your URL"));
// Imports
// ...
public class MyFrame extends JFrame
{
public MyFrame()
{
super("Test");
setDefaultCloseOperation(EXIT_ON_CLOSE);
try
{
URL url = new URL("http://upload.wikimedia.org/wikipedia/it/0/0b/Vegeta_-_Sigla_Iniziale_Dragon_Ball_Kai.jpg");
getContentPane().add(new JLabel(new ImageIcon(url)));
}
catch(Exception ex)
{
ex.printStackTrace();
}
pack();
setLocationRelativeTo(null);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(() ->
{
new MyFrame().setVisible(true);
});
}
}

JPanel created on click not appearing

The below code is not my actual code but a concise, runnable remake of what I am trying to achieve. I want the JPanel CP, an instance of clickPanel, to appear when the user clicks on the image in JPanel hasAnImage. I can see in the Netbeans console that the is executing because of the Sys.out.print, but nothing appears on the screen. I have tried setting visible to false then true again and revalidate() in the mousePressed event; the image moves to the left, but nothing appears on the screen. The goal is for CP to appear. What am I missing? Hope my question is clear.
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.BorderFactory;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class Testo extends JFrame{
public Testo(){
BufferedImage image = null;
try {
image = ImageIO.read(new File("C:\\Users\\someimage.jpg"));
} catch (IOException ex) {
ex.printStackTrace();
}
;
final JLabel label = new JLabel(new ImageIcon(image));
JPanel hasAnImage = new JPanel();
hasAnImage.addMouseListener(new MouseAdapter(){
#Override //I override only one method for presentation
public void mousePressed(MouseEvent e) {
clickPanel CP = new clickPanel();
hasAnImage.add(CP);
revalidate();
//setVisible(false);
//setVisible(true);
}
});
hasAnImage.add(label);
add(hasAnImage);
setVisible(true);
}
public static void main(String[] args) {
Testo frame = new Testo();
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
frame.getContentPane().setBackground(Color.WHITE);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public class clickPanel extends JPanel{
public clickPanel() {
setPreferredSize(new Dimension(100,60));
setMaximumSize(new Dimension(100,60));
setBackground(new Color(1.0f,1.0f,1.0f,0.1f));
setBorder(BorderFactory.createMatteBorder(2,2,2,2,Color.GREEN));
System.out.println("This is being executed...");
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setFont(new Font("Arial", Font.PLAIN, 12));
g.setColor(Color.GREEN);
g.drawString("CLICK", 2, 2);
}
}
}

Beyond revalidate();ing the pane, you also need to repaint(); it. Thus your mousePressed method should become:
public void mousePressed(MouseEvent e) {
clickPanel CP = new clickPanel();
hasAnImage.add(CP);
revalidate();
repaint();
}
For further reading: http://docs.oracle.com/javase/7/docs/api/java/awt/Component.html#repaint()

How to set repeating background image to a JPanel?

I want to set an image which repeats throughout the full width of the JPanel like we apply Background image to a DIV in CSS. How do I obtain that in swing for a JPanel?

Swing doesn't provide this functionality out of the box, so you will need to do it yourself...
The overall process is relative simple,
for (y = 0 to containerHeight) do
for (x = 0 to containerWidth) do
drawImage(tile, x, y)
The fun part is knowing where and how to apply it. Take a look at:
Performing Custom Painting
2D Graphics
Reading/Loading an Image
For details about the various parts you will need to know.
Example
So using this as the tile...
I was able to produce this...
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class PaintTitle {
public static void main(String[] args) {
new PaintTitle();
}
public PaintTitle() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private BufferedImage tile;
public TestPane() {
try {
tile = ImageIO.read(getClass().getResource("/tile.jpg"));
} catch (IOException ex) {
ex.printStackTrace();
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
int tileWidth = tile.getWidth();
int tileHeight = tile.getHeight();
for (int y = 0; y < getHeight(); y += tileHeight) {
for (int x = 0; x < getWidth(); x += tileWidth) {
g2d.drawImage(tile, x, y, this);
}
}
g2d.dispose();
}
}
}

Layering text over JLabel

This is how I want my app to look like.
Trouble is, if I drag the JLabel with the "Hello, I'm Myra" over another JLabel (whose icon is the speech bubble), rather than superimposing or layering, NetBeans shifts the JLabels to be adjacent.
How do I superimpose ie. place the text JLabel on top of another JLabel?
Do note, I'm using NetBeans. It doesn't allow me to edit much of the JFrame or JLabel code.

Netbeans won't let you add components to a JLabel, it doesn't see them as a valid Container.
This won't be easily achieved using component labels, as the icon placement is outside of your control. A better solution might be to use a custom component, such as a JPanel and manually draw the speech bubble image yourself, then using a combination of Border and LayoutManager it would allow you to add other components to it
This is a very basic example...
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;
public class SpeechBubble {
public static void main(String[] args) {
new SpeechBubble();
}
public SpeechBubble() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
SpeechBubblePane bubble = new SpeechBubblePane();
JLabel hello = new JLabel("Hello, I'm Myra");
hello.setFont(hello.getFont().deriveFont(28f));
hello.setForeground(Color.CYAN);
JLabel message = new JLabel("<html>What would you like to know today?</html>");
message.setFont(message.getFont().deriveFont(22f));
message.setForeground(Color.WHITE);
bubble.setLayout(new GridLayout(2, 1));
bubble.add(hello);
bubble.add(message);
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setBackground(Color.BLACK);
frame.add(bubble);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class SpeechBubblePane extends JPanel {
private BufferedImage background;
public SpeechBubblePane() {
setOpaque(false);
try {
background = ImageIO.read(getClass().getResource("/speechbubble.png"));
} catch (IOException ex) {
ex.printStackTrace();
}
setBorder(new EmptyBorder(19, 19, 66, 19));
}
#Override
public Dimension getPreferredSize() {
Dimension size = new Dimension(200, 200);
if (background != null) {
size = new Dimension(background.getWidth(), background.getHeight());
}
return size;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (background != null) {
Graphics2D g2d = (Graphics2D) g.create();
int x = (getWidth() - background.getWidth()) / 2;
int y = (getHeight()- background.getHeight()) / 2;
g2d.drawImage(background, x, y, this);
g2d.dispose();
}
}
}
}
If I was doing this, I would consider developing up a "9-path" which would allow you to break the image down into 9 parts and scale the outer sections based on what the content requires, for example...

It sounds like you just want to add a z-order. If so, you need a LayeredPane:
http://docs.oracle.com/javase/7/docs/api/index.html
http://docs.oracle.com/javase/7/docs/api/javax/swing/JLayeredPane.html

Jbutton acction listener

I am trying to create a form. there is a button that when clicking the button, a photo which is specified would appear. my problem is, when I click the button, the picture pops up and if the cursor passes the form boundary, the image disappears. here is my code:
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import static java.lang.Math.abs;
import static java.lang.Math.min;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
public class SeamCarving extends JFrame
{
public static void main(String[] args) throws IOException {
final BufferedImage input = ImageIO.read(new File("path"));
final BufferedImage[] toPaint = new BufferedImage[]{input};
final Frame frame = new Frame("Seams") {
#Override
public void update(Graphics g) {
final BufferedImage im = toPaint[0];
if (im != null) {
g.clearRect(0, 0, getWidth(), getHeight());
g.drawImage(im, 0, 0, this);
}
}
};
frame.setSize(input.getWidth(), input.getHeight());
frame.setVisible(true);
frame.add(startButton);
startButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
BufferedImage out = input;
out = deleteVerticalSeam(out);
toPaint[0] = out;
frame.repaint();
System.out.println("Do Something Clicked");
}
});
}
}

Don't override update, this isn't how painting is achieved in Swing. Attempting to paint directly to a top level container like JFrame is problematic at best.
Instead, start with a JPanel and use it's paintComponent method instead. Make sure you call super.paintComponent as well.
In fact, you could probably just use a JLabel to display the image instead.
Take a look at;
Performing Custom Painting
How to use labels
For more details
Updated with example
I still think a JLabel would be simpler solution, but what do I know.
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class SeamCarving {
public static void main(String[] args) {
new SeamCarving();
}
public SeamCarving() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private BufferedImage input;
private BufferedImage[] toPaint;
public TestPane() {
try {
input = ImageIO.read(new File("C:\\hold\\thumbnails\\2005-09-29-3957.jpeg"));
toPaint = new BufferedImage[1];
} catch (IOException ex) {
ex.printStackTrace();
}
setLayout(new GridBagLayout());
JButton startButton = new JButton("Start");
startButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
BufferedImage out = input;
out = input; //deleteVerticalSeam(out);
toPaint[0] = out;
repaint();
System.out.println("Do Something Clicked");
}
});
add(startButton);
}
#Override
public Dimension getPreferredSize() {
return input == null ? new Dimension(400, 400) : new Dimension(input.getWidth(), input.getHeight());
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (toPaint[0] != null) {
Graphics2D g2d = (Graphics2D) g.create();
g2d.drawImage(input, 0, 0, this);
g2d.dispose();
}
}
}
}
The problem with overriding update is the paint subsystem can choose to avoid calling and end up calling paint directly, circumventing your painting.
Painting also involves painting child components (like your button) and borders, which you've conveniently discarded by not calling super.update.