In the following code, I call JOptionPane.showMessageDialog, inside a try/catch block. But when the error is caught, my JOptionPane is visible but without any message !!! Does someone knows why and how I can correct the problem ?
Regards
MyBoardJPannel.java
package experimentations.gui;
import java.awt.Graphics;
import java.awt.Image;
import java.io.InputStream;
import javax.imageio.ImageIO;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class MyBoardPannel extends JPanel {
#Override
public void paint(Graphics grahics) {
if (imageToShow == null)
imageToShow = loadImage("sampleImage");
}
/**
* In fact, there are not any image in project => will go to catch clause.
* #param imageName
*/
private void loadImage(String imageName) {
InputStream imageStream = getClass().getResourceAsStream("/"+imageName+".png");
try {
imageToShow = ImageIO.read(imageStream);
}
catch (Exception e) {
String errorMessage = "Failed to load image "+imageName;
System.err.println(errorMessage);
JOptionPane.showMessageDialog(this, errorMessage,
"Image loading error", JOptionPane.ERROR_MESSAGE);
imageToShow = null;
System.exit(1);
}
}
private Image imageToShow;
}
JOptionPaneErrorShowing.java
package experimentations.gui;
import javax.swing.JFrame;
public class JOptionPaneErrorShowing extends JFrame {
public JOptionPaneErrorShowing(){
setTitle("JOptionPane experimentation");
setSize(300, 300);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
add(new MyBoardPannel());
}
/**
* #param args
*/
public static void main(String[] args) {
new JOptionPaneErrorShowing().setVisible(true);
}
}
It's likely a Swing concurrency issue. But more importantly, you should never load an image from within a paint or paintComponent method, ever. Read it in the constructor or elsewhere but paint/paintComponent need to be lean and blazingly fast.
To solve your issue, consider reading in the image in SwingWorker object. If you call a JOptionPane from within the SwingWorker's doInBackground method though, be sure to call it on the Swing event thread, the EDT, using SwingUtilities.invokeLater(Runnable).
Also, you will hardly ever want to draw in a JPanel's paint method unless you are taking care of painting borders and children. Instead paint in a paintComponent method, and don't forget to call the super.paintComponent(g) method in that paintComponent override. You'll want to read the Swing graphics tutorials as this is all spelled out there.
For example:
import java.awt.Graphics;
import java.awt.Image;
import java.io.InputStream;
import java.util.concurrent.ExecutionException;
import javax.imageio.ImageIO;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
public class MyBoardPannel extends JPanel {
protected static final String SAMPLE_IMAGE = "sampleImage";
Image imageToShow = null;
public MyBoardPannel() {
SwingWorker<Image, Void> mySW = new SwingWorker<Image, Void>() {
#Override
protected Image doInBackground() throws Exception {
return loadImage(SAMPLE_IMAGE);
}
#Override
protected void done() {
try {
imageToShow = get();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
};
mySW.execute();
}
#Override
public void paintComponent(Graphics grahics) {
super.paintComponent(grahics);
if (imageToShow != null) {
grahics.drawImage(imageToShow, 0, 0, null);
}
}
private Image loadImage(String imageName) {
InputStream imageStream = getClass().getResourceAsStream(
"/" + imageName + ".png");
try {
return ImageIO.read(imageStream);
} catch (Exception e) {
final String errorMessage = "Failed to load image " + imageName;
System.err.println(errorMessage);
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JOptionPane.showMessageDialog(MyBoardPannel.this, errorMessage,
"Image loading error", JOptionPane.ERROR_MESSAGE);
System.exit(1);
}
});
}
return null;
}
}
I don't really know, but maybe your panel you use as parent of the JOptionPane (by passing this) is invisible or there is something else wrong. Try adding pack(); at the end of your JOptionPaneErrorShowing constructor.
What I know is that I had this problem when I was using an old Ubuntu and old Nvidia driver for my GPU, when the desktop effects were turned on (the Compiz Fusion of today. I don't know if it was already called Compiz, that long ago).
Aha! I found it, you are displaying the error inside the repaint method. Never do that! Load your image inside the constructor of the MyBoardPanel class and show error messages over there.
Related
I recently started to use multithreading in Java and I've run into a problem I assume is due to missing synchronization.
This is a ImageLoader I wrote:
package util;
import javax.swing.ImageIcon;
public class ImageLoader extends Thread {
private String file;
private ImageIcon icon;
public ImageLoader(String file) {
this.file = file;
}
#Override
public void run() {
ImageIcon icon = new ImageIcon(this.file);
this.icon = icon;
super.run();
}
public synchronized ImageIcon returnIcon() {
return this.icon;
}
}
I use this ImageLoader in my GUI-Class:
package gui;
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import util.ImageLoader;
public class HauptGui extends JComponent {
public HauptGui() {
initUI();
}
private void initUI() {
int bilderAnzahl = 3;
this.setLayout(new GridLayout(1, 1));
JPanel bilderPanel = new JPanel(new GridLayout(bilderAnzahl, 1));
for (int i = 0; i < bilderAnzahl; i++) {
JLabel jbl = new JLabel();
ImageLoader loader = new ImageLoader("./Picture.jpg");
loader.start();
jbl.setIcon(loader.returnIcon());
jbl.setBorder(BorderFactory.createEtchedBorder());
jbl.setPreferredSize(new Dimension(200, 50));
bilderPanel.add(jbl);
}
JScrollPane scrPn = new JScrollPane(bilderPanel);
this.add(scrPn);
}
}
The Problem is that the returnIcon-Method of the ImageLoader gets called before the Thread calls the run-Method, therefore the ImageIcon is still null.
How do I synchronize this?
No, your problem has nothing to do with synchronization and all to do with simply requesting the image object before it has been created. The solution is to get the image object in a call-back, after it has completed its loading. A SwingWorker would work well in this situation, where you get the image object from the SwingWorker in the worker's done method by calling .get() on it, or you could use a PropertyChangeListener for your callback. See Lesson: Concurrency in Swing for the details on how to use SwingWorkers.
For example (code not tested)
public class ImageLoader2 extends SwingWorker<BufferedImage, Void> {
private String path = ""; /// String to resource path
public BufferedImage doInBackground() throws Exception {
return ImageIO.read(ImageLoader2.class.getResource(path));
}
}
and then run it like:
ImageLoader2 loader = new ImageLoader2();
loader.addPropertyChangeListener(pce -> {
if (evt.getNewValue() == SwingWorker.StateValue.DONE) {
try {
BufferedImage img = loader.get();
ImageIcon icon = new ImageIcon(img);
// use icon here...
} catch catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
// handle exception here
}
}
});
loader.execute();
Side notes
you should almost never extend Thread.
Don't get the image as a File as you are doing but rather get it as a resource and use ImageIO.read(...) to do this
The resource path is relative to the class-path, not to the user's directory, and so it will likely be different from the path you use to get the image as a file.
To be clear, I've been researching for more than five hours now, I read all the related questions and more than 20 google searches, none of them worked for me and none of them described my case specifically.
First of all here's my code :
import java.util.*;
import java.applet.*;
import java.awt.*;
import java.awt.image.*;
import java.io.IOException;
import static Debug.StaticVar.*;
/*
<applet code="ImageTest" width=300 height=100>
</applet>
*/
public class ImageTest extends Applet {
Image img;
MediaTracker tracker;
public void init() {
tracker = new MediaTracker(this);
Thread Loader = new Thread(() -> {
img = getImage(getCodeBase(), "1.jpg");
tracker.addImage(img, 1);
});
Loader.setPriority(10);
Loader.start();
}
public void start() {
try {
tracker.waitForAll();
repaint();
} catch (InterruptedException e) {
}
}
public void paint(Graphics g) {
g.drawImage(img, 0, 0, null);
}
}
My Problem is the repaint method not calling paint method. To be more specific the paint method executes if I call repaint from another thread, or if I add the paint method to a child class and call repaint but it doesn't work in my code, where I directly call it from the applet main thread. Please HEEEEELP, I'm tired
I've recently been experimenting with the user of JTextPanes for an upcoming project I'll be working on, there have been various posts online detailing how to go about counting the number of lines within the text pane however the solutions I found all seem to fail when inserting Icons or Components into the text pane's document.
The solution I found that worked for plain text was this one (with the solution implemented of course): BadLocationException when using Utilities.getRowStart On hit of Enter key
However once I try to insert a Component (JLabel) or a plain Icon for that matter, the getRowStart() method from Utilities throws a null pointer exception. What I find unusual about this is the Java Doc states that "...This is represented in the associated document as an attribute of one character of content. ", so I assumed it would treat it as any other character but it seems this is not the case.
I've included a code example to replicate the problem if anyone would like to try it. I have a feeling that it just simply isn't possible, which would be a shame.
import java.awt.Dimension;
import java.awt.Image;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextPane;
import javax.swing.text.BadLocationException;
import javax.swing.text.Utilities;
public class Test{
private JFrame frame;
private JTextPane textPane;
private Image img;
private URL imgURL;
public Test(){
frame = new JFrame();
frame.setSize(new Dimension(500,300));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
textPane = new JTextPane();
try {
imgURL = new URL("http://www.freeiconspng.com/uploads/floppy-save-icon--23.png");
img = ImageIO.read(imgURL);
JLabel label = new JLabel(new ImageIcon(img.getScaledInstance(10, 10, Image.SCALE_SMOOTH)));
textPane.insertComponent(label);
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
frame.getContentPane().add(textPane);
frame.setVisible(true);
}
public JTextPane getTextPane(){
return this.textPane;
}
public int getLineCount(){
int totalCharacters = textPane.getDocument().getLength();
int lineCount = (totalCharacters == 0) ? 1 : 0;
try {
int offset = totalCharacters;
while (offset > 0) {
offset = Utilities.getRowStart(textPane, offset) - 1;
lineCount++;
}
} catch (BadLocationException e) {
e.printStackTrace();
}
return lineCount;
}
public static void main(String[] args){
Test t = new Test();
t.getLineCount();
}
}
The problem was solved after the following comment:
It doesn't throw any exception for me once I wrap the content inside
your main method inside a EventQueue.invokeLater() call. I.e.:
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
Test t = new Test();
t.getLineCount();
}
});
Hi I have googled and can't figured out why my paintComp method isnt being called
I have the following code
package com.vf.zepto.view;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Properties;
import javax.imageio.ImageIO;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import com.vf.zepto.view.interfaces.ProcessorPanel;
public class CountryDetailsPanel extends JPanel implements ProcessorPanel, Runnable {
private GridBagConstraints c = new GridBagConstraints();
private String countryName;
private Properties prop = new Properties();
private BufferedImage image;
public CountryDetailsPanel() {
try {
prop.load(new FileInputStream("country.props"));
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
//this.setLayout(new GridBagLayout());
c.gridx = 0;
c.gridy = 0;
c.fill = GridBagConstraints.BOTH;
c.insets = new Insets(5, 5, 5, 5);
this.setPreferredSize(new Dimension(200, 200));
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
try {
if(countryName != null) {
String asset = prop.getProperty(countryName+".flag");
if(!asset.equals(null)) {
image = ImageIO.read(new File(asset));
g.drawImage(image, 0, 0, null);
}
}
}
catch (IOException e) {
e.printStackTrace();
}
}
#Override
public void updateDetails(Object o) {
countryName = (String)o;
SwingUtilities.invokeLater(this);
}
#Override
public void run() {
this.repaint();
}
}
and when calling this.repaint() expect the paintComponent method to be called but for love nor money it isnt.
Have tried to force it to use the EDT incase that was the issue but its not.
any ideas?
You should never call paintComponent() the repaint() method consolidates all requests to change the component (there may be several repaint requests between screen refreshes). It adds an update request to the GUI event queue so that the update will be properly coordinated with other GUI actions (Swing and AWT are not thread-safe). This update request, when processed, calls update(), which calls paint(), which calls your paintComponent()
Why have this:
#Override
public void run() {
this.repaint();
}
It does not seem of any use (creating a new thread to repaint once? Not to mention the thread is not on EDT rather call repaint() on the JPanel instance (if modified externally other than that you shouldnt even worry). However to start a thread which modifeis UI componets use s SwingTimer/SwingWorker or SwingUtilities#invokeXXX()
This might not be related but in your code I see this:
if(!asset.equals(null)) {
image = ImageIO.read(new File(asset));
g.drawImage(image, 0, 0, null);
}
dont use equals() to compare to a null value as this might throw a NullPointerException because you are attempting to
deference a null pointer, for example this code throws a NPE:
String s=null;
if(!s.equals(null)) {//throws NPE
System.out.println("Here");//is never printed
}
Also as mKorbel has said (+1 to him) dont do long running tasks in paintComponent() declare your Image globally, assign it in the constructor and then use it in paintComponent(). F.i
rather do:
public class TestPanel extends JPanel {
private Image image;
public TestPanel() {
image = ImageIO.read(new File(asset));
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
if(asset!=null) {
g.drawImage(image, 0, 0, null);
}
}
}
Do not load image or another hard or long running code in paintComponent
Load this Object as a local variable and only one time
paintComponent() is called
implicitly, when JComponent requires repaint, or
explicitly, for example on every of mouse event if one were to invoke paintComponent() from a MouseMotionListener.
If there is animation, then to use Swing Timer and call repaint().
when you download a resource in a Java Webstart application there's usually a download progress window displayed which shows the progress of the download. If this window is the default progress window, it has a cancel button. I'm basically trying to implement this cancel button in a custom download progress window.
As there is no method which you could call to cancel the download, I tried to find out how this was done in the default progress window. Because of the implementation with a ServiceManager it's a bit tricky to find the actual implementation. But I finally found this: [jdk-source on googlecode (DownloadServiceImpl)].
When you search for "cancel" or just scroll down to the progress method you will see that it should be as easy as throwing a RuntimeException. Sadly this doesn't really work. It just stops the progress method from being called. The resource is still downloaded in the background and the loadPart method never returns.
If you want to try this for yourself, I've prepared a small example. You will need some sort of webserver though (a local webserver is sufficient of course). I have tried this on a Windows XP (32 bit) with Java 1.6.0_21 (and apache tomcat 6).
A simple jnlp file would look like this (you probably want to change the port):
<?xml version="1.0" encoding="utf-8"?>
<jnlp
spec="1.0+"
codebase="http://127.0.0.1:8080/DownloadTest"
href="DownloadTest.jnlp"
version="1.0">
<information>
<title>DownloadTest</title>
<vendor>Download Tester</vendor>
</information>
<resources os="Windows">
<java version="1.6.0_18+" href="http://java.sun.com/products/autodl/j2se" />
<jar href="DownloadTest.jar" main="true"/>
<jar href="largeResource.jar" download="lazy" part="One"/>
</resources>
<application-desc main-class="downloadtest.Main">
</application-desc>
</jnlp>
Next you will need a large file as resource (the content doesn't matter at all). For example on many windows machines you you will find "driver.cab" under "Windows\Driver Cache\i386". The file must be added to a jar archive (jar -cf largeResource.jar <input file>).
The main program looks like this (you will need to include jnlp.jar as lib, which you can find at <jdk_home>\sample\jnlp\servlet):
package downloadtest;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import javax.jnlp.DownloadService;
import javax.jnlp.DownloadServiceListener;
import javax.jnlp.ServiceManager;
import javax.jnlp.UnavailableServiceException;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.SwingWorker;
public class Main {
private static DownloadService downloadService;
private static DownloadServiceListener customDownloadWindow;
static {
try {
downloadService = (DownloadService) ServiceManager.lookup("javax.jnlp.DownloadService");
} catch (UnavailableServiceException ex) {
System.err.println("DownloadService not available.");
}
customDownloadWindow = new CustomProgress();
}
public static void main(String[] args) {
JFrame frame = new JFrame("DownloadTest");
frame.setBounds(0, 0, 200, 100);
frame.setDefaultCloseOperation(JDialog.EXIT_ON_CLOSE);
frame.setLayout(null);
JButton startDownload = new JButton("download");
startDownload.setBounds(20, 20, 150, 40);
startDownload.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
new SwingWorker<Void, Void>() {
#Override
protected Void doInBackground() {
try {
downloadService.loadPart("One", customDownloadWindow);
//downloadService.loadPart("One", downloadService.getDefaultProgressWindow());
} catch (IOException ex) {
ex.printStackTrace();
System.err.println("IOException loadPart.");
}
return null;
}
}.execute();
}
});
frame.add(startDownload);
frame.setVisible(true);
}
}
You can try each download progress window by uncommenting one "downloadService.loadPart..." line and commenting out the other one.
And finally the custom progress window itself:
package downloadtest;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.URL;
import javax.jnlp.DownloadServiceListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.SwingUtilities;
public class CustomProgress implements DownloadServiceListener {
JFrame frame = null;
JProgressBar progressBar = null;
boolean uiCreated = false;
boolean canceled = false;
public CustomProgress() {
}
private void create() {
JPanel top = createComponents();
frame = new JFrame(); // top level custom progress indicator UI
frame.getContentPane().add(top, BorderLayout.CENTER);
frame.setBounds(300,300,400,300);
frame.pack();
updateProgressUI(0);
}
private JPanel createComponents() {
JPanel top = new JPanel();
top.setBackground(Color.WHITE);
top.setLayout(new BorderLayout(20, 20));
String lblText = "<html><font color=green size=+2>JDK Documentation</font>" +
"<br/> The one-stop shop for Java enlightenment! <br/></html>";
JLabel lbl = new JLabel(lblText);
top.add(lbl, BorderLayout.NORTH);
progressBar = new JProgressBar(0, 100);
progressBar.setValue(0);
progressBar.setStringPainted(true);
top.add(progressBar, BorderLayout.CENTER);
JButton cancelButton = new JButton("Cancel");
cancelButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
CustomProgress.this.canceled = true;
}
});
top.add(cancelButton, BorderLayout.SOUTH);
return top;
}
public void progress(URL url, String version, long readSoFar,
long total, int overallPercent) {
updateProgressUI(overallPercent);
}
public void upgradingArchive(java.net.URL url,
java.lang.String version,
int patchPercent,
int overallPercent) {
updateProgressUI(overallPercent);
}
public void validating(java.net.URL url,
java.lang.String version,
long entry,
long total,
int overallPercent) {
updateProgressUI(overallPercent);
}
public void downloadFailed(URL url, String string) {
System.err.println("Download failed");
}
private void updateProgressUI(int overallPercent) {
if (overallPercent > 0 && overallPercent < 99) {
if (!uiCreated) {
uiCreated = true;
// create custom progress indicator's UI only if
// there is more work to do, meaning overallPercent > 0 and < 100
// this prevents flashing when RIA is loaded from cache
create();
}
progressBar.setValue(overallPercent);
if (canceled) {
throw new RuntimeException("canceled by user");
}
SwingUtilities.invokeLater(new Runnable() {
public void run() {
frame.setVisible(true);
}
});
} else {
// hide frame when overallPercent is above 99
SwingUtilities.invokeLater(new Runnable() {
public void run() {
if (frame != null) {
frame.setVisible(false);
frame.dispose();
}
}
});
}
}
}
This is basically taken from an Oracle tutorial (http://download.oracle.com/javase/tutorial/deployment/webstart/customProgressIndicatorForAppln.html). I just added a cancel button.
When you build this as a jar file and put it together with the largeResource.jar and DownloadTest.jnlp in a public folder of your webserver, you should be able to start the application via your web browser. Then click the download button and before it is finished click the cancel button in the download window. After trying the custom progress window you will need to remove the application (or just the resource) from your Java cache (because the resource is downloaded in the background regardless of clicking the cancel button).
So, why is this working with the default progress window but not with the custom progress window? Is there an easy possibility to cancel a download with a custom download window?
Any help or hints appreciated.
Drax
Ok, took a look at the Google sample you showed and found this at the bottom of the class
/*
* Progress Helper class
*
* The DownloadServiceListerner interface defined in the JNLP API is
* a subset of the DownloadProgressWindow interface used by elsewhere.
*
* this class is used to create a Helper object that implements both.
*/
private class ProgressHelper extends CustomProgress {
private DownloadServiceListener _dsp = null;
public ProgressHelper() {
_dsp = null;
}
public ProgressHelper(DownloadServiceListener dsp) {
setAppThreadGroup(Thread.currentThread().getThreadGroup());
setListener(dsp);
_dsp = dsp;
if (_dsp instanceof DefaultProgressHelper) {
((DefaultProgressHelper) _dsp).initialize();
}
// for bug #4432604:
_dsp.progress(null, null, 0, 0, -1);
}
public void done() {
if (_dsp instanceof DefaultProgressHelper) {
((DefaultProgressHelper) _dsp).done();
} else {
// make sure callbacks to DownloadServiceListener have
// been called before returning (for TCK test)
flush();
}
}
}
And what is interesting is that it looks like it sets the current thread's ThreadGroup as the application thread group. So this leads me to believe that by doing this the actual download is kept closer to the application (not sure what the correct terminology would be) such that the RuntimeException throw in the class in the cancel check really does affect it.
Otherwise, my hunch is that in your application the download actually takes place in another thread and is "unaffected" by the Exception thrown by your application, hence, allowing it to complete.