Develop Reference

How to stop recursive SwingWorker method? JavaFX

I'm using a recursive method which implements the use of the SwingWorker class to do a research in one folder and all its subfolders - in the local hard drive.
Basically works fine but I'm stuck when I want to stop the SwingWorker method: when the user change the 'source folder' (I'm using a JTree - JAVAFX - to show all the folders in the local hard drive), I want to stop the current 'SwingWorker research' in that folder and start a new one, with the newest 'source path' results choosed from the user.
All the results of the research are stored in a private ObservableList - and updated everytime in the done() method, just by filling one TableView - JavaFX: so, when the user change the 'source path' I have to clean the results of the previous research.
Start method:
private static ObservableList<msg> data = FXCollections.observableArrayList();
private static SwingWorker<Void, Void> worker;
private static String currentFolder;
#Override
public void start(Stage primaryStage) throws Exception {
// TODO Auto-generated method stub
stage = primaryStage;
primaryStage.setScene(new Scene(createContent()));
styleControls();
primaryStage.initStyle(StageStyle.UNDECORATED);
primaryStage.setMaximized(true);
primaryStage.setFullScreen(false);
primaryStage.show();
msgp = new MsgParser();
}
createContent() method- recursive function its called here:
public Parent createContent() {
tree.getSelectionModel().selectedItemProperty().addListener( new ChangeListener<Object>() {
#Override
public void changed(ObservableValue observable, Object oldValue,
Object newValue) {
TreeItem<File> selectedItem = (TreeItem<File>) newValue;
currentFolder = selectedItem.getValue().getAbsolutePath();
// I want to stop here the previous SwingWorker call : the tree
// ChangeListener event is called when the user change the
// source folder of the research, by selecting one TreeItem on it.
if(worker!= null)
worker.cancel(true);
//Here I clean previous results
data.clear();
TV.setItems(data);
//And I call again the method with the new source Folder
ListMail(new File(currentFolder));
}
});
}
ListMail() method: [recursive SwingWorker]
private void ListMail(File dir) {
worker = new SwingWorker<Void, Void>() {
#Override
protected Void doInBackground() throws Exception {
File[] directoryListing = dir.listFiles();
if (directoryListing != null) {
for (File child : directoryListing) {
if(!worker.isCancelled()) {
if(child != null){
if(!child.isDirectory()) {
if(child.getAbsolutePath().substring(child.getAbsolutePath().lastIndexOf('.')+1).equals("msg")) {
Message message = msgp.parseMsg(child.getPath());
String percorsoMail = child.getAbsolutePath().toUpperCase();
if(message != null) {
String fromEmail = message.getFromEmail();
String fromName = message.getFromName();
String subject = message.getSubject();
String received = message.getDate().toString();
String name;
if(fromEmail != null)
name = fromName + "(" + fromEmail + ")";
else name = fromName;
msg Message = new msg(name, subject, received);
if(!data.contains(Message))
data.add(Message);
//I use the Platform.runLater to
// take count of the number of results found
//It updates the GUI - works fine
Platform.runLater(new Runnable() {
#Override public void run() {
if(data != null && data.size() > 0)
setStatusLabel(data.size());
else
setStatusLabel(0);
}
});
}
}
} else {
/**
* Recursive call here : I do the research
* for the subfolders
*/
ListMail(child);
}
} else {
}
}
}
}
return null;
}
// Update GUI Here
protected void done() {
// I refresh here the TableView: works fine on-the-fly added results
TableView.setItems(data);
TableView.refresh();
}
};
//This doesn't do anything
if(!worker.isCancelled())
worker.execute();
}
Basically, the issue is that the SwingWorker thread never stop, I'm thinking because of the recursive calls which creates new pid process at every run or something ?
Also by using a dedicated external button, which I prefer to avoid, gives no results:
refreshBtn.setOnAction(e -> {
//Handle clicks on refreshBtn button
worker.cancel(true);
});
After I click on TreeItem to change source-folder, it just delete all the ObservableList elements created at that moment, but the previous research don't stop.
Everything works fine instead if I wait the research its finished - but this can works only when I'm in a deep-level folder, while I can't obviously wait when the research start with the "C:\" folder.

Ok so that's here how I managed this by using javafx.concurrent.
Just to point my experience with this, it seems using a recursive background Task for potentially long computations, such as scanning the Whole local drive like in my example, it's very memory consuming - also because I stored some results of this background computation in static local variables to access them faster: the result was a data-structure (ObservableList) with over 5000+ instances of a custom class to represent that specific data computed and then the OutOfMemoryError message or the background thread just going like in 'stand-by' without any advice after running for long time (waiting for garbage collection?).
Anyway here's the code that sum up how I solved: the threads are correctly closed. By the way, sometimes, there's a little 'GUI delay' due to cleaning the GUI on the isCancelled() method check: the GUI swing between clear/not clear, because in my opinion it keeps get filled by the results of the previous tasks in the recursion.
private static BackgroundTask backgroundTask;
private static Thread thread;
tree.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<Object>() {
#Override
public void changed(final ObservableValue observable, final Object oldValue, final Object newValue) {
//I close previous running background tasks if there's any
if (backgroundTask != null) {
while (backgroundTask.isRunning()) {
backgroundTask.cancel(true);
// reset GUI nodes here used to show results of the previous thread
}
}
backgroundTask = new BackGoundTask();
thread= new Thread(backgroundTask);
thread.setDaemon(true);
thread.start();
//This will be called only when latest recursion is finished, not at every run
backgroundTask.setOnSucceeded(e -> {});
}
});
BackgroundTask class:
public static class BackgroundTask extends Task<Object> {
// .. variables used by the task here
//constructor: initialize variables at every run of the Task
public BackgroundTask() {
}
#Override
protected Object call() throws Exception {
if (!isCancelled()) {
// ... Do all background work here
Platform.runLater(new Runnable() {
#Override
public void run() {
// GUI progress can goes here
}
});
//recursion here
if(something) {
//...
} else {
call();
}
} else {
//user want to cancel task: clean GUI nodes
}
return null;
}
}

Matlab & Java: Execute matlab asynchronously

so, here is my today problem:
First of all, please note that I do NOT have the Matlab parallel toolbox available.
I am running java code witch interact with Matlab. Sometime Matlab directly call some java functions, sometimes it is the opposite. In this case, we use a notification system which comes from here:
http://undocumentedmatlab.com/blog/matlab-callbacks-for-java-events
We then address the notification in proper callbacks.
Here is a simple use case:
My user select a configuration file using the java interface, loaded into Matlab.
Using an interface listener, we notify Matlab that the configuration file has been selected, it then run a certain number of functions that will analyzes the file
Once the analysis is done, it is pushed into the java runtime, which will populate interface tables with the result. This step involve that matlab will call a java function.
Finally, java request the interface to be switched to an arbitrary decided tab.
This is the order of which things would happen in an ideal world, however, here is the code of the listener actionPerformed method:
#Override
public void actionPerformed(ActionEvent arg0) {
Model wModel = controller.getModel();
Window wWindow = controller.getWindow();
MatlabStructure wStructure = new MatlabStructure();
if(null != wModel) {
wModel.readMatlabData(wStructure);
wModel.notifyMatlab(wStructure, MatlabAction.UpdateCircuit);
}
if(null != wWindow) {
wWindow.getTabContainer().setSelectedComponent(wWindow.getInfosPannel());
}
}
What happen here, is that, when the notifyMatlab method is called, the code does not wait for it to be completed before it continues. So what happen is that the method complete and switch to an empty interface page (setSelectedComponent), and then the component is filled with values.
What I would like to, is for java to wait that my notifyMatlab returns a "I have completed !!" signal, and then pursue. Which involves asynchrounous code since Matlab will code java methods during its execution too ...
So far here is what I tried:
In the MatlabEventObject class, I added an isAcknowledge member, so now the class (which I originaly found in the above link), look like this (I removed all unchanged code from the original class):
public class MatlabEventObject extends java.util.EventObject {
private static final long serialVersionUID = 1L;
private boolean isAcknowledged = false;
public void onNotificationReceived() {
if (source instanceof MatlabEvent) {
System.out.println("Catched a MatlabEvent Pokemon !");
MatlabEvent wSource = (MatlabEvent) source;
wSource.onNotificationReceived();
}
}
public boolean isAcknowledged() {
return isAcknowledged;
}
public void acknowledge() {
isAcknowledged = true;
}
}
In the MatlabEvent class, I have added a future task which goal is to wait for acknowledgement, the methods now look like this:
public class MatlabEvent {
private Vector<IMatlabListener> data = new Vector<IMatlabListener>();
private Vector<MatlabEventObject> matlabEvents = new Vector<MatlabEventObject>();
public void notifyMatlab(final Object obj, final MatlabAction action) {
final Vector<IMatlabListener> dataCopy;
matlabEvents.clear();
synchronized (this) {
dataCopy = new Vector<IMatlabListener>(data);
}
for (int i = 0; i < dataCopy.size(); i++) {
matlabEvents.add(new MatlabEventObject(this, obj, action));
((IMatlabListener) dataCopy.elementAt(i)).testEvent(matlabEvents.get(i));
}
}
public void onNotificationReceived() {
ExecutorService service = Executors.newSingleThreadExecutor();
long timeout = 15;
System.out.println("Executing runnable.");
Runnable r = new Runnable() {
#Override
public void run() {
waitForAcknowledgement(matlabEvents);
}
};
try {
Future<?> task = service.submit(r);
task.get(timeout, TimeUnit.SECONDS);
System.out.println("Notification acknowledged.");
} catch (Exception e) {
e.printStackTrace();
}
}
private void waitForAcknowledgement(final Vector<MatlabEventObject> matlabEvents) {
boolean allEventsAcknowledged = false;
while(!allEventsAcknowledged) {
allEventsAcknowledged = true;
for(MatlabEventObject eventObject : matlabEvents) {
if(!eventObject.isAcknowledged()) {
allEventsAcknowledged = false;
}
break;
}
}
}
}
What happen is that I discover that Matlab actually WAIT for the java code to be completed. So my waitForAcknowledgement method always wait until it timeouts.
In addition, I must say that I have very little knowledge in parallel computing, but I think our java is single thread, so having java waiting for matlab code to complete while matlab is issuing calls to java functions may be an issue. But I can't be sure : ]
If you have any idea on how to solve this issue in a robust way, it will be much much appreciated.

Handle concurrent events in Java

I'm having a problem with my Java code.
I need to execute my doSomething() method, which includes code that manage also global variables. The problem is that the method is invoked twice (both mouseEvent and focusEvent of my JTable are fired at the same time).
How can I execute the doSomething() method only once at a time, in a sort of mutual exclusion ?
Thanks.
addMouseListener (new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
doSomething();
}
});
addFocusListener(new FocusAdapter() {
#Override
public void focusLost(FocusEvent e){
doSomething();
}
});
JTable cells contains String with length 1 or 2.
I need to apply a setValue method (or delete the String), in the exact moment the user stops the cell editing or he writes a 2 character String.
With those listeners I know the exact time to do the setValue or to inform the user that the first character he wrote doesn't exist. So in that way I wanted to block the user's action.
In other words, I need to control the user input in order to do a setValue or delete it. FocusLost tells me when the user clicks outside the JTable Component.
MouseClicked tells me when the user clicks in the JTable Component.
When mouseClicked is invoked and the JOptionPane appears, the cell automatically lose the focus, and so also the focusLost is invoked.
public void doSomething () {
// inEdit and tableCellEdited are the global variables
if ( inEdit && tableCellEdited != null ) {
String temp = "" + tableCellEdited.getDay();
String s = tableCellEdited.getValRenderer().trim();
if (s.length() > 2) s = s.substring(4);
if ( !s.trim().isEmpty() ) {
JOptionPane.showMessageDialog(getParent(),
"Code doesn't exist" , "Error: Code doesn't exist",JOptionPane.WARNING_MESSAGE);
tableCellEdited.setRendererValue(getUltimaGG(), false);
}
else {
tableCellEdited.setRendererValue(s, false);
setValueAt(tableCellEdited, getRowFromMat(tableCellEdited.getMat()), Integer.parseInt(temp.substring(6, 8)) );
}
clearProgrammazioneDueCaratteri();
}
}
repaint();
}

replace handleEvent(Event e) by processEvent(AWTEvent e)

I can't find a way to transform the code when replacing the deprecated functionhandleEvent withprocessEvent. can anyone help?
how to get x, y and the id of the event on processEvent?
here is my function:
public boolean handleEvent(Event evt) {
if (evt.target == this) {
// move floatting text zone
if (dragingTextZone == true) {
this.posStr.x = evt.x;
this.posStr.y = evt.y;
repaint(this.posStr.x,
this.posStr.y,
1000,
(int) (_imageViewer.getCurrent_font().getSize() * _imageViewer.getScalefactor()));
if (evt.id == Event.MOUSE_DOWN) {
dragingTextZone = false;
addTextToPicture();
}
}
if (evt.id == Event.MOUSE_DRAG) {
if (dragitem.isDragging()) {
repaint(dragitem.getX(),
dragitem.getY(),
dragitem.getWidth(),
dragitem.getHeight());
dragitem.drag(evt.x, evt.y);
repaint(dragitem.getX(),
dragitem.getY(),
dragitem.getWidth(),
dragitem.getHeight());
}
}
else {
if (evt.id == Event.MOUSE_UP) {
// setting crop zone
if (dragingCropZone || dragingMask) {
endDrag(evt);
}
else if (dragingLine) {
addLineToPicture();
endDrag(evt);
}
}
if (evt.id == Event.MOUSE_DOWN) {
if (getEditMode() == EDTMODE_ALL) {
if (evt.modifiers == Event.CTRL_MASK) {
startDragHighLight(evt);
}
else if (evt.modifiers == Event.ALT_MASK) {
startDragLine(evt);
}
else {
if (clickedOnFocusedItem(evt)) {
startDragMask(evt);
}
}
}
}
}
}
return super.handleEvent(evt); // This passess the mouse click back up to Applet
}
Thank you,

Rather than a single Event class that includes everything, the new (relatively speaking - it's been around since Java 1.1) AWTEvent approach is to have different subclasses of AWTEvent for different purposes. In your case it's the MouseEvent subclass you're interested in, so you would need to call enableEvents(AWTEvent.MOUSE_EVENT_MASK | AWTEvent.MOUSE_MOTION_EVENT_MASK) to enable handling of the relevant events, then override processMouseEvent and processMouseMotionEvent to do the handling.
But the preferred way to handle events is not to override the process* methods but rather to register separate listener objects. In your case you would create another class (possibly an inner class inside your main one) which is a subclass of MouseAdapter, override the relevant event hook methods in that, then register an instance of the adapter class by calling both addMouseListener and addMouseMotionListener on the main component.
There is extensive documentation on the Oracle website (and elsewhere) on how to implement event handling in an AWT or Swing application.

How to change JButton property?

I want to change button text when i click on it, but it does not appears on the GUI. In intellje IDE i can see it is changed but why does not appear in GUI?
This is code snip:
final WebLabel loading = new WebLabel("Disconnected...", IconLib.ICON_19X17_THICK_ARROW_RIGHT_LIGHTBLUE.getIcon(), SwingConstants.CENTER);
final WebLabel ipLabel = new WebLabel(host);
final JPanel horizontalMiddlePanel = new JPanel();
final WebButton disconnect = new WebButton("Connect", IconLib.ICON_16X16_QUESTIONMARK_ON_BLUE_CIRCLE.getIcon());
disconnect.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (loading.getText().equals("Connected...")) {
loading.setText("Disconnected...");
loading.setIcon(IconLib.ICON_19X17_THICK_ARROW_RIGHT_LIGHTBLUE.getIcon());
disconnect.setText("Connect");
} else {
loading.setText("test");
loading.setIcon(IconLib.ICON_19X17_THICK_ARROW_RIGHT.getIcon());
ipLabel.setText(ipLabel.getText().replace(" Unreachable try again",""));
ipLabel.setForeground(Color.green);
disconnect.setText("Connecting");
callflexConnection(ipLabel, 3001, loading, disconnect);
}
}
});

than not possible without spliting code to to the two parts
1) update JButton#setText
then
2) executing rest of code
by delaing by using javax.swing.Timer
execute from SwingWorker
wrap inside Runnble#Thread,
3) this code is executed on EDT, then all changes are done on EDT, end in same/one moment

It's hard to tell if it's the source of your current problem or not, but performing logic in code based on the current text on a button is a flimsy way to do things. You should maintain that connection state in a dedicated variable. Something like this:
private enum ConnState {
CONN_DISCONNECTED,
CONN_CONNECTING,
CONN_CONNECTED,
};
private ConnState connState;
private void setConnState(ConnState connState) {
this.connState = connState;
switch (connState) {
case CONN_DISCONNECTED:
loading.setText("Disconnected");
disconnect.setText("Connect");
break;
case CONN_CONNECTING:
loading.setText(...etc...);
disconnect.setText(...);
break;
case CONN_CONNECTED:
loading.setText(...);
disconnect.setText(...);
break;
}
}
And call this when setting up the GUI to initialize the button text and connState:
setConnState(CONN_DISCONNECTED);
Then you can reason robustly about the current state of the program by checking the connState variable instead of having to synchronize button strings everywhere.