We Keep Coding

On JavaFX, how to hide stage without disposing it and closing the application?

I need to creat an app that shows the primary stage to the user, and if the user closes the stage, instead of finishing the application, it should just hide the stage for later use.
On swing we could just call setVisible(false) to a JFrame or JDialog, but how to do it on JavaFX?

Once the JavaFX toolkit has started, by default it will close down when the last visible window is closed.
To prevent this, you can call
Platform.setImplicitExit(false);
You typically do this in your start(...) method, though it can be called from any thread.
To exit the application, you would then need to call
Platform.exit();
(as the application no longer exits automatically).

Window Close Listener And setDefaultCloseOperation

I have a question about the relationship between swing window listener and default close operation. The question occurs when I am dealing with below scenario:
I add a window listener (WindowAdapter is used for the listener) for a JFrame, and override the windowClosing function: if the user closes the window, a dialog will pop up to confirm, if user chooses CANCEL option, then directly return. However, when I test the code and choose CANCEL when closing the window, the frame window is still closed (or maybe just invisible, because the Java icon is still in the task bar).
Then I add the default close option with DO_NOTHING_ON_CLOSE, with the same test behavior, the frame window is not closed, which is what I expected.
setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);
Then I change the default close option with EXIT_ON_CLOSE, with the same test behavior, the frame window is directly closed(this time Java icon also disappeared).
This makes me confused. Does it mean the window listener can just define what to do when the window is closing but can't determine whether to close the window? Or I need to override other function?

The window listener is just a listener. It does not affect the default close operation, unless you actually change the default close operation in the windowClosing() code.
I use:
frame.setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);
as the default when the frame is created. Then in the windowClosing(...) method, if the user confirms the closing of the frame I change the default:
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
Check out Closing an Application for more information and more complete example code.

Problems with the modality of a JDialog (mouse events for main window both fired and buffered)

I made a JDialog and the modality works presumably fine
dialog.setModalityType(JDialog.ModalityType.APPLICATION_MODAL);
dialog.setVisible(true);
But then my problem is:
I´m throwing Jdialog after a jcombobox.setSelection() and I need to click twice in Accept button in order to hide the dialog, because dropdown popup is consuming the first click for closing himself. I fixed it by manually calling jcombobox.hidePopup() before calling the dialog, but I cannot understand if the later is modal, why the mouse events trigger things outside the window?`
My Main window buffers somehow the mouse events, so for those mouse events which are not activated when the modal dialog is drawn (as happens with the previous point), it seems they get buffered and are applied after dialog closure. Is this an expected behavior?
Thank u!

replace jcombobox.hidePopup("doesn't make me sence") with ActionListener or ItemListener added to the JComboBox
add RequestFocusListener by #camickr for setting the FocusOwner correctly
for why reasons are there another MouseListeners, maybe in the case that fird any events to the JComponents that you can't to set Focus correctly

How to show popup on other popup?

In my application, on some screen, I launch a popup. Depends on what button the user will click on this popup, another popup has to be launched. I use JDialog object to implement these popups. The issue is that the second popup doesn't show up (even though is use setVisible(true) and toFront()). It's created but I can't see it. I defined in its constructor the first popup as its owner. Anyone can help?

When a JDialog is opened from a parent window or dialog, and set to be modal, the Event Dispatch Thread for the parent window is halted. This prevents the parent from being focused or from passing other events, or essentially doing anything until the modal dialog is closed. The call is therefore blocking.
What you must do instead is fire your event from somewhere else, like the new dialog instead of the parent window, OR instead of using modal dialogs, use a regular JFrame and set it to be always on top using setAlwaysOnTop(true). That means the user can continue to use the parent window, and events will still fire from it.
Addendum: in response to your problem "the program concentrates in showing it and doesn't react to the event that has to hide it": when you make a dialog modal, as soon as you make it visible, it will block the parent window until it is closed, including event firing. If you need the new popup to be closed programatically, you either need to make the popup non-modal, or you need to execute the subsequent code in the context of the new popup window (such as firing an event when it becomes visible)

OK, now I managed to show the second popup. The code in the event that triggers the popup is:
printingWindow.setLocationRelativeTo(null);
printingWindow.toFront();
printingWindow.setModal(true);
printingWindow.pack();
printingWindow.setVisible(true);
But now I have a different problem:
when the printingWindow is set to be visible, the program concentrates in showing it and doesn't react to the event that has to hide it.
The code that is executed when the appropriate event is fired is:
printingWindow.setVisible(false);
printingWindow.dispose();
So how I close this popup (by firing the event)?

how to know if JDialog is closed or not?

I have used a JDialog to display a form ( I could have used JFrame, but I have my reasons). There is an event in my application that will cause a function to generate and display the said JDialog. Now, I want to know if the user has closed that JDialog. How do I find this out?
P.S. My defaultCloseOperation is JDialog.DISPOSE_ON_CLOSE.

Register a window listener on the dialog, and implement the windowClosed method, see The Java Tutorial on Window Listeners