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JavaFx Progress Indicator freezes when I run another thread

So I have been trying to implement a progress indicator with no luck. I am not sure I understand managing threads with JavaFx very well, despite having read a bit about the Platform.RunLater and Tasks. So here is my use case.
My program allows users to connect to a database and look at some of the schemas and other objects in the database. Sometimes connecting to a large database and pulling up all its tables and info takes a while, so I would like to show a progress indicator. I am not trying to update the progress at all I would just like to make the progress indicator visible at a value of -1 while the process is running to pull everything from the database. Ideally I will have a progress indicator loaded in from an FXML file invisible. When I start the process of pulling info from the database I would like to make it visible.
When trying to make my progress visible it never showed up, so I decide to start out having it visible and making it invisible, just to see what happens. The progress indicator rotated nicely when I opened the program up, but as soon as I try to connect to the database it stopped rotating and just froze. I assume this is what happens when I try to make it visible too which is why it was never showing up.
The following is my current code, I would appreciate any detailed help with explanations so I can understand what is going on. Thanks
from the method that is doing most of the work.
//make progress indicator visible
pi.setVisible(true);
// separate non-FX thread
ExtractorThread t = new ExtractorThread();
t.setCp(cp);
t.start();
//Wait until the thread is done
try{
t.join();
}
catch(Exception e){
e.printStackTrace();
}
//Retrieve the dbextractor from the thread
DbExtractor dbe = t.getDbe();
//move on to the next page in the application
this.caster.goToDataSource(c, cp, dbe);
The ExtractorThread which does the work.
private class ExtractorThread extends Thread{
private ConnectionProperties cp;
private DbExtractor dbe;
public void run() {
dbe = new DbExtractor(cp);
try {
dbe.extract();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public DbExtractor getDbe() {
return dbe;
}
public void setCp(ConnectionProperties cp) {
this.cp = cp;
}
}
If I am supposed to use the Platform.RunLater I am not sure where to use it or why. Any help would be appreciated, thanks!

Use the javafx.concurrent API. Extend Task instead of Thread:
private class ExtractorThread extends Task<DbExtractor>{
private ConnectionProperties cp;
public DbExtractor call() throws Exception {
dbe = new DbExtractor(cp);
dbe.extract();
return dbe;
}
public void setCp(ConnectionProperties cp) {
this.cp = cp;
}
}
Then do:
//make progress indicator visible
pi.setVisible(true);
// separate non-FX thread
final ExtractorThread t = new ExtractorThread();
t.setCp(cp);
t.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
public void handle(WorkerStateEvent event) {
DbExtractor dbExtractor = t.getValue();
this.caster.goToDataSource(c, cp, dbe);
}
});
t.setOnFailed(...); // similarly, to handle exceptions
new Thread(t).start();

I don't code JavaFX, and so I can't give you chapter and verse, but this line:
t.join();
will block the calling code until the background thread is through. Don't do this. Instead use some type of listener to get notified when the background thread finishes. If this were Swing, I'd use a PropertyChangeListener added to a SwingWorker to notify me when the background thread was done. I think that you can still use a PropertyChangeListener to do a similar thing with with JavaFX, but I cannot tell you if this would represent the canonical solution.
Also, don't extend Thread but instead implement Runnable. This won't fix your problem but is basic Java common sense.

Manipulation with JProgressBar in Swing

I have an app that connects reads file on remote server. File dynamically updates that's why I use Timer class to reread this file periodically.
Workflow is the following:
Open window where text will be displayed.
Start reading file (reread once per 15 sec using Timer)
In 15 seconds window is filled with data or I receive exceptions in log. Exceptions are suppressed and I continue trying to read data.
Exceptions are my problem, because user doesn't know what is happening now with an app.
There are at least two Exceptions I ran at:
- If file is absent, I receive FileNotFoundException.
- If server is on maintenance I receive other Exception (I catch it, so its name doesn't matter).
Here is how above looks like in code:
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
final RemoteReader reader = new RemoteReader();
Timer timer = new Timer(15000, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
try {
reader.getMainPanel().readData();
} catch (IOException e) {
//Here is a counter that increases after each exception throw
if(counter >5) {
JOptionPane.showOptionDialog(chat,
e.getMessage(),
e.getClass().getName(),
JOptionPane.OK_CANCEL_OPTION,
JOptionPane.INFORMATION_MESSAGE,
null,
new String[]{"Retry", "Cancel"}, //on Retry - make another 5 tries to read file, on cancel - close the window
null);
counter = 0;
}
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
}
}
});
timer.start();
}
});
}
public String readData() throws IOException {
// read and process data before returning it
// but for test purpose:
//BufferedReader br = new BufferedReader(new InputStreamReader(this.url.openStream()));
throw new IOException("cannot read file");
}
What I want to do is to add JProgressBar. On openning the main window progress bar appears and then data is read. If IOException throws 5 times in a row, show option dialog. Otherwise hide progress bar and show data. If remote file becomes unavailable, show option dialog. And pressing the retry button, show progress bar... then workflow starts from the very beginning.
Some code examples would help me, but I don't expect solution for the whole issue - advice, how it should be done in right way from design point of view will be enough. Samples of Oracle a little bit vague for me.

Even if WatchService, seen here, is not available, I'd still use SwingWorker, seen here and here.
You have considerable latitude in pacing the doInBackground() thread, e.g. Thread.sleep(15 * 1000).
You can setProgress() in the background and listen for any PropertyChangeEvent in the GUI.
You can update any GUI components in process(), which runs on the EDT.

SwingWorker ends, PropertyChangeListener listens, but how do I get back to EDT?

I've already browsed many threads on this topic, but nothing seems to fit my specific situation.
I have a swing application which analyzes QR-Codes, extracts the found loginNames and makes DB calls to fetch data for that user. To make sure the capture of the QR-Codes can be canceled and my application is still accessible while capturing, I used a SwingWorker for this purpose. Everything works fine so far, I've included a PropertyChangeListener so the application knows when my SwingWorker successfully read a code. But since I don't want to have the PropertyChangeListener as a nested class within my mainClass (to keep it well structured), I've created a new class for it outside. Now I want to return to my main class from this PropertyChangeListener class to switch to the appropriate panel which displays the fetched data. I have different codes which can be read, so depending on the code I have different panels to switch to (so I can't do a static switch to the same panel over and over again). So how can I delegate the PropertyChangeListener to give the control back to my EDT ?
I've tried using wait() and notify() to let my EDT know the SwingWorker finished. But obviously wait() blocks my EDT and the use of SwingWorker is pointless.
I hope I could explain my problem in enough detail, and some of you have a good idea to deal with this.
For any code snippets please ask, I'll then add the necessary ones. But since my project is a bit more complex I'll just post what is asked for.
Thanks in advance for any help :)
EDIT: Here is a code excerpt to illustrate what my SwingWorker is doing.
SwingWorker class:
public class CodeDetector extends SwingWorker<byte[], String> {
String s; // read String
byte[] completeCode; // byte[] which is returned by doInBackground()
BufferedImage resizedImg;
IplImage img;
JLabel labelForStream;
JLabel result;
FrameGrabber grabber = new VideoInputFrameGrabber(); // using JavaCV.
public CodeDetector(JLabel labelForStream, JLabel result) {
this.labelForStream = labelForStream;
this.resultLabel = result;
}
#Override
protected byte[] doInBackground() throws Exception {
try {
grabber.start(); //
while (true) {
// End if current thread was canceled.
if (Thread.currentThread().isInterrupted()) {
return null;
}
// Grab each image, save it, scan for code and display it.
img = grabber.grab();
resizedImg = // resizing image to fit labelForStream.
// save resizedImg to file
// read barcode from saved file
if (isBadgeCode(tmp) || isDeviceCode(tmp)) {
s = tmp;
} else {
continue;
}
break;
} catch (NotFoundException e) {
// Code could not be encoded yet.
}
...
// end worker after timeout
// show image on window
if (img != null) {
labelForStream.setIcon(new ImageIcon(resizedImg));
}
}
}
} catch (Exception e) {
System.err.println("Error: " + e.getMessage() + " - " + e.getStackTrace() + " - " + e.getClass());
}
return s != null ? s.getBytes() : null;
}
#Override
protected void done() {
try {
completeCode = get();
if (completeCode != null) {
String code = new String(completeCode);
if (isOtherCode(code)) {
resultLabel.setText(code);
} else if (isUsernameCode(code)) {
// Cut userName from read code (if previously verified) and set label text.
resultLabel.setText(verify(code, true) ? code.split(":")[0] : null);
}
} else {
resultLabel.setText(null);
}
resultLabel.setVisible(true);
resultLabel.updateUI();
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
} catch (CancellationException e) {
return;
} catch (Exception e) {
e.printStackTrace();
}
}
As this SwingWorker doesn't have references to any panels, even though the done()-method is done in EDT, I need to somehow notify my mainClass that a code has been read successfully and that it can change the panl now according to the specific code.
Hope this clears things up a bit.

I think that you misunderstood, for what reasons SwingWorker is there, please read SwingWorker
tutorial, where implementations quite guarentee that output from methods:
done()
process()
publish()
setProgress()
should be done on EDT

The simple swing worker answer is to override the done() method. That is executed on the EDT - SwingWorker takes care of that for you.
You can do it yourself, using SwingUtilities.invokeLater.
For the way you pose your question, I suspect you don't have a full grasp of the threading issues and how you switch between threads. So a good review of the tutorial (if you haven't already) may be in order.

This is wrong:
protected byte[] doInBackground() throws Exception {
// ....
if (img != null) {
labelForStream.setIcon(new ImageIcon(resizedImg));
}
// ....
}
As this shows you making critical Swing calls from within the doInBackground method, something that should never be done. Instead consider publishing the Image or the ImageIcon, and setting the JLabel's Icon from the process method override.
As I note in my comment, sometimes its a good idea to use a PropertyChangeListener with your SwingWorker if it decreases code coupling. This is one reason that SwingWorker has its own PropertyChangeSupport and its own state enum.

JButton stays in pressed state

In my Java GUI app I have a JButton and when clicked it calls a function to connect to a database, then calls a function to clear a table in the DB, then calls a function that reads text from one file and loads variables, which calls a function that reads text from another file, compares the data from both and then calls a function to either update or insert data in the DB, all of that works fine.
However my question is related to the JButton, when its clicked I want to run a Indeterminate progress bar just so the user knows work is being done and then right before it leaves the the action listener setIndeterminate to false and set the value of the progress bar to 100(complete), but in my case when you click the button it stays in the clicked state and the progress bar freezes.
What should I implement to prevent this? threading possibly? but Im quite new to threading in java. here is my action listener:
private class buttonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
if( e.getSource() == genButton )
{
progressBar.setIndeterminate(true);
progressBar.setString(null);
try
{
dbConnect(); //connects to DB
clearSchedules(); // deletes data in tables
readFile(); // reads first file and calls the other functions
dbClose();// closes the DB
progressBar.setIndeterminate(false);
progressBar.setValue(100);
}
catch (Exception e1){
System.err.println("Error: " + e1.getMessage());
}
}
}
}
On a side note, I would like to have the action bar actually move as the the program progresses but I wasnt sure how to monitor its progress.
Thanks, Beef.
UPDATE here is my example of SwingWorker and how I used it:
Declared globally
private functionWorker task;
private abstract class functionWorker extends SwingWorker {
public void execute() {
try {
dbConnect();
} catch (SQLException e) {
e.printStackTrace();
}
clearSchedules();
try {
readFile();
} catch (IOException e) {
e.printStackTrace();
}
dbClose();
}
}
Inside my actionPerformed method
if( e.getSource() == genButton )
{
progressBar.setIndeterminate(true);
progressBar.setString(null);
try
{
task.execute();
progressBar.setIndeterminate(false);
progressBar.setValue(100);
}
catch (Exception e1){
System.err.println("Error: " + e1.getMessage());
}
}

The problem is probably related to connecting to doing expensive operations in the UI thread (connecting to a database, reading from a file, calling other functions). Under no circumstances should you call code that uses excessive CPU time from the UI thread, as the entire interface can't proceed while it is executing your code, and it results in a 'dead' looking application, with components remaining in their state at the time before an expensive operation until completion. You should execute another thread, do the expensive work in that, and then use a SwingUtilities.invokeLater(Runnable doRun) with a passed runnable where you'd update the progress.
There may be synchronisation issues relating to the states of components, but you can fix these later.

Could I create the new thread when the action is performed and call the new functions in the thread, or should I do the threading within the actual function itself?
You can start a SwingWorker from your button's handler, as shown here. A related example implementing Runnable is seen here.

One method to handle progressbars are to extend SwingWorker in a class.
SwingWorker takes care of running background tasks for you and so you do not have to implement your own threading that can end up in unknown issues.
To begin with, your class that takes care of progress bar UI should implement PropertyChangeListener
And implement public void propertyChange(PropertyChangeEvent evt) { - to update the progressbar status based on a global variable.
The background task class should look like the following(this could be an inner class) :
class ProgressTask extends SwingWorker<Void, Void> {
#Override
public Void doInBackground() {
//handle your tasks here
//update global variable to indicate task status.
}
#Override
public void done() {
//re-enabled your button
}
}
on your button's event listener :
public void actionPerformed(ActionEvent evt) {
//disable your button
//Create new instance of "ProgressTask"
//make the task listen to progress changes by task.addPropertyChangeListener(this);
//calll task.execute();
}
I have tried to water down code example, you would have to read some tutorial to understand how all these pieces fit together. However, the main point is do not code your Threads, instead use SwingWorker

progressBar.setIndeterminate(true);
progressBar.setValue(0);
dbConnect(); //connects to DB
progressBar.setIndeterminate(true);
progressBar.setValue(10);
clearSchedules(); // deletes data in tables
progressBar.setIndeterminate(true);
progressBar.setValue(50);
readFile(); // reads first file and calls the other functions
progressBar.setIndeterminate(true);
progressBar.setValue(75);
dbClose();// closes the DB
progressBar.setIndeterminate(false);
progressBar.setValue(100);
You will need to tell the progress bar how much progress has been made because it does not know the percentage completed. Better yet, write a method that updates and repaints the progress bar rather than repeating the method calls here.
updateProgressBar(int progress, boolean isDeterminate, String msg){};
You will also need to make sure that your specific button is firing the action performed.
class IvjEventHandler implements java.awt.event.ActionListener {
public void actionPerformed(java.awt.event.ActionEvent e) {
if (e.getSource() == JMyPanel.this.getJButtonUpdate())
connEtoC1(e);
};
};
The connEtoC1(e); should execute a controller class or SwingWorker rather than firing from the GUI

JTabbedPane: Actions performed before displaying selected tab

When one of the panels present in a JTabbedPane is clicked, I need to perform a few actions at the start. Say, for example, I need to check the username and password. Only if those match, the particular panel operations need to be performed. Can you suggest any methods?

Not sure I fully understand your question, but I would do something like:
Add a ChangeListener to the JTabbedPane to listen for the first tab click.
When a ChangeEvent occurs perform the login on a background thread using a SwingWorker.
If the login is successful perform the required UI operations on the Event dispatch thread.
For example:
tabbedPane.addChangeListener(new ChangeListener() {
private boolean init;
public void stateChanged(ChangeEvent e) {
if (!init) {
init = true;
new SwingWorker<Boolean, Void>() {
#Override
protected void done() {
try {
boolean loggedIn = get();
if (loggedIn) {
// Success so perform tab operations.
}
} catch (InterruptedException e1) {
e1.printStackTrace(); // Handle this.
} catch (ExecutionException e1) {
e1.printStackTrace(); // Handle this.
}
}
protected Boolean doInBackground() throws Exception {
// Perform login on background thread. Return true if successful.
return true;
}
}.execute();
}
}
});

The action to change the tab is triggered by a mouse listener in the UI class. it goes through and checks whether there is a tab at the clicked coordinate and if so, whether the tab is enabled. If that criteria is met, it will call setSelectedIndex(int) on your JTabbedPane. In order to intercept the tab changing, what you can do is override setSelectedIndex(int) to trigger a permissions check. Once the permissions are validated, you can make a call to super.setSelectedIndex(int). this should do what you want.
please note that if the permissions check is a long running call (ie a call to a database or a server), you should use something like a SwingWorker break up your processing, so that the permissions check is done off the AWT EventQueue and the call to super.setSelectedIndex(int) is done on the AWT EventQueue.