Best way to detect browser closing/navigation to other page and do logout

Question

I am writing an application in GWT and I need to detect when a user navigates away from my application or when he closes the browser window (onUnload event) and do a logout

Answer 1

The way to do that is to use the Window.addWindowClosingHandler like @Carnell and @BillLyons said. But I use an additional technique to detect if the browser has been closed or if the page is being visited again (by refresh or back navigation).

Following there's an utility class that can help you. Just call the lines below in your onModuleLoad to test.

The use example:

@Override
public void onModuleLoad() {
    if (BrowserCloseDetector.get().wasClosed()) {
        GWT.log("Browser was closed.");
    }
    else {
        GWT.log("Refreshing or returning from another page.");
    }
}

The utility class:

import com.google.gwt.user.client.Cookies;
import com.google.gwt.user.client.Window;

public class BrowserCloseDetector {
    private static final String COOKIE = "detector";
    private static BrowserCloseDetector instance;

    private BrowserCloseDetector() {
        Window.addWindowClosingHandler(new Window.ClosingHandler() {
            public void onWindowClosing(Window.ClosingEvent closingEvent) {
                Cookies.setCookie(COOKIE, "");
            }
        });
    }

    public static BrowserCloseDetector get() {
        return (instance == null) ? instance = new BrowserCloseDetector() : instance;
    }

    public boolean wasClosed() {
        return Cookies.getCookie(COOKIE) == null;
    }
}