A JLabel allows HTML contents, which can contain an image among the contents:
String html = "<html><body>...<img src=\"http://some_url/image.png\"/>...</body></html>";
JLabel label = new JLabel(html);
Note that I use the JLabel for rendering images in a JXTreeTable, so the updating of the text of the JLabel is done on the EDT in the renderer.
The problem is that the image gets loaded synchronously. With a slow server, the EDT can be blocked for multiple seconds while the image is being loaded.
I already discovered why the image gets loaded synchronously, and which class I need to modify to switch to async loading of images.
The loading of the image is done by the javax.swing.text.html.ImageView class, which has a method setLoadsSynchronously.
The problem is that I have no clue how I can easily adjust the HTMLFactory / HTMLEditorKit which is responsible for creating that ImageView, and which is used internally by the JLabel .
To make matters even more complicated, I need a solution which works for all Look and Feels.
In case the above is not clear, the following thread dump shows on what the EDT is blocked during the image retrieval:
"AWT-EventQueue-0@999" prio=6 tid=0x10 nid=NA waiting
java.lang.Thread.State: WAITING
at java.lang.Object.wait(Object.java:-1)
at java.awt.MediaTracker.waitForID(MediaTracker.java:677)
at javax.swing.ImageIcon.loadImage(ImageIcon.java:314)
at javax.swing.ImageIcon.setImage(ImageIcon.java:381)
at javax.swing.text.html.ImageView.loadImage(ImageView.java:704)
at javax.swing.text.html.ImageView.refreshImage(ImageView.java:673)
at javax.swing.text.html.ImageView.sync(ImageView.java:645)
at javax.swing.text.html.ImageView.getPreferredSpan(ImageView.java:443)
at javax.swing.text.FlowView$LogicalView.getPreferredSpan(FlowView.java:732)
at javax.swing.text.FlowView.calculateMinorAxisRequirements(FlowView.java:233)
at javax.swing.text.ParagraphView.calculateMinorAxisRequirements(ParagraphView.java:717)
at javax.swing.text.html.ParagraphView.calculateMinorAxisRequirements(ParagraphView.java:157)
at javax.swing.text.BoxView.checkRequests(BoxView.java:935)
at javax.swing.text.BoxView.getMinimumSpan(BoxView.java:568)
at javax.swing.text.html.ParagraphView.getMinimumSpan(ParagraphView.java:270)
at javax.swing.text.BoxView.calculateMinorAxisRequirements(BoxView.java:903)
at javax.swing.text.html.BlockView.calculateMinorAxisRequirements(BlockView.java:146)
at javax.swing.text.BoxView.checkRequests(BoxView.java:935)
at javax.swing.text.BoxView.getMinimumSpan(BoxView.java:568)
at javax.swing.text.html.BlockView.getMinimumSpan(BlockView.java:378)
at javax.swing.text.BoxView.calculateMinorAxisRequirements(BoxView.java:903)
at javax.swing.text.html.BlockView.calculateMinorAxisRequirements(BlockView.java:146)
at javax.swing.text.BoxView.checkRequests(BoxView.java:935)
at javax.swing.text.BoxView.getMinimumSpan(BoxView.java:568)
at javax.swing.text.html.BlockView.getMinimumSpan(BlockView.java:378)
at javax.swing.text.BoxView.calculateMinorAxisRequirements(BoxView.java:903)
at javax.swing.text.html.BlockView.calculateMinorAxisRequirements(BlockView.java:146)
at javax.swing.text.BoxView.checkRequests(BoxView.java:935)
at javax.swing.text.BoxView.getPreferredSpan(BoxView.java:545)
at javax.swing.text.html.BlockView.getPreferredSpan(BlockView.java:362)
at javax.swing.plaf.basic.BasicHTML$Renderer.<init>(BasicHTML.java:383)
at javax.swing.plaf.basic.BasicHTML.createHTMLView(BasicHTML.java:67)
at javax.swing.plaf.basic.BasicHTML.updateRenderer(BasicHTML.java:207)
at javax.swing.plaf.basic.BasicLabelUI.propertyChange(BasicLabelUI.java:417)
at javax.swing.plaf.synth.SynthLabelUI.propertyChange(SynthLabelUI.java:296)
at java.beans.PropertyChangeSupport.fire(PropertyChangeSupport.java:335)
at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:327)
at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:263)
at java.awt.Component.firePropertyChange(Component.java:8428)
at org.jdesktop.swingx.renderer.JRendererLabel.firePropertyChange(JRendererLabel.java:292)
at javax.swing.JLabel.setText(JLabel.java:330)
The image is only part of the HTML…calling
setIconis not an option.
One approach would be to load the image in the background of a SwingWorker, save it temporarily to the file system, and reference the saved file in the <img/> tag. The variation below, adapted from this example, is a proof of concept. Your actual implementation might employ a SwingWorker<List<Row>, Row>, where each Row contains an image File; your doInBackground() implementation would publish() interim results as they become available; your implementation of process() would ensure that the relevant tree-table renderer sees the correct File for a given Row.
import java.awt.*;
import java.awt.image.*;
import java.io.*;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.*;
/**
* @see http://stackoverflow.com/questions/4530659 */
public class WorkerTest extends JFrame {
private JPanel panel = new JPanel();
private JLabel label = new JLabel("Loading...");
public WorkerTest() {
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
label.setHorizontalTextPosition(JLabel.CENTER);
label.setVerticalTextPosition(JLabel.CENTER);
this.add(label);
this.pack();
this.setLocationRelativeTo(null);
}
private void start() {
new ImageWorker().execute();
}
public static void main(String args[]) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
WorkerTest wt = new WorkerTest();
wt.setVisible(true);
wt.start();
}
});
}
class ImageWorker extends SwingWorker<File, Void> {
private static final String TEST =
"http://cdn.sstatic.net/stackexchange/img/logos/so/so-logo.png";
private BufferedImage image;
private File file;
@Override
protected File doInBackground() throws IOException {
image = ImageIO.read(new URL(TEST));
file = File.createTempFile("image", null);
ImageIO.write(image, "png", file);
return file;
}
@Override
protected void done() {
label.setText("<html><body><img src=\"file://"
+ file.getAbsolutePath() + "\"/></body></html>");
panel.setPreferredSize(new Dimension(image.getWidth(), image.getHeight()));
WorkerTest.this.pack();
WorkerTest.this.setLocationRelativeTo(null);
}
}
}