Question

Is there a way to detect if a browser window is closed using GWT. For example a window opened through GWT using this code:

Window.open("some_url", "__blank", null);

I need to detect wether this windows opened through gwt is closed. Is there a way to do that?

Answer 1

I think, it is a real problem making it cross-browser.
GWT has

 Window.addCloseHandler(new CloseHandler<Window>() {
            public void onClose(CloseEvent<Window> windowCloseEvent) {

            }
        });

Which handles the onunload event(occurs before the browser closes the document).
However it does not work for handling browser close event with all browsers, because when refreshing the page, this event is fired as well.

Since GWT also generates JavaScript see this article: Window Close Event of Browser
Here is conclusion of that article:

Conclusion

As we have already discussed that there is no 100% fool proof way to
detect the browser close event in a lot of cases, the above technique
can fail. For example if the user kills the browser’s process from
task manager, there could be many more cases. Yet in a lot of cases,
this technique can be handy. Best of luck and happy programming.