How to stop a stage from closing

Question

I want to trap the clicking of "X" on the window and possibly stop the window closing. I've got this code:
@Override
public void start(final Stage stage) throws Exception {
Parent root = FXMLLoader.load(getClass().getResource("demo.fxml"));
Scene scene = new Scene(root);
stage.setScene(scene);
stage.setTitle("Demo");
stage.setScene(scene);
stage.onCloseRequestProperty().set(new EventHandler<WindowEvent>() {
@Override
public void handle(WindowEvent e) {
System.err.println("A");
stage.setOnCloseRequest(new EventHandler<WindowEvent>() {
@Override
public void handle(WindowEvent ev) {
System.err.println("B");
stage.onHidingProperty().set(new EventHandler<WindowEvent>() {
@Override
public void handle(WindowEvent e) {
System.err.println("C");
stage.setOnHiding(new EventHandler<WindowEvent>() {
@Override
public void handle(WindowEvent ev) {
System.err.println("D");
@Override
public void stop() throws Exception {
System.err.println("E");
super.stop();
When "X" is clicked on the window, this prints
B
D
E
If I add an Event.consume() here:
stage.setOnCloseRequest(new EventHandler<WindowEvent>() {
@Override
public void handle(WindowEvent ev) {
System.err.println("B");
ev.consume()
and run I now get this:
B
The program '<unknown>' received an X Window System error.
This probably reflects a bug in the program.
The error was 'GLXBadDrawable'.
(Details: serial 113 error_code 149 request_code 136 minor_code 5)
(Note to programmers: normally, X errors are reported asynchronously;
that is, you will receive the error a while after causing it.
To debug your program, run it with the --sync command line
option to change this behavior. You can then get a meaningful
backtrace from your debugger if you break on the gdk_x_error() function.)
I'm running Java on Linux:
java version "1.7.0_17"
Java(TM) SE Runtime Environment (build 1.7.0_17-b02)
Java HotSpot(TM) 64-Bit Server VM (build 23.7-b01, mixed mode)

Answer 1

When "X" is clicked on the window, this prints
B
D
E
This is the expected behavior.
If I add an Event.consume() here:
stage.setOnCloseRequest(new EventHandler<WindowEvent>() {
@Override
public void handle(WindowEvent ev) {
System.err.println("B");
ev.consume()
});and this is the correct way to veto the request to close the stage...
>
and run I now get this:
B
The program '<unknown>' received an X Window System error.
This probably reflects a bug in the program.But this is a bug. You should file a JIRA for this. It's probably worth upgrading to the latest version of the JDK available, both the stable release (JDK 1.7.0 u21) and also try with the latest snapshot release of JDK 8 (b88 currently); this will give you an idea as to whether this has already been fixed.
FWIW, it works for me: I'm running JDK 1.7.0 u21 on Mac OS X; but this level of window events necessarily involve some interaction with the native windowing toolkit.