onHistoryChanged() not being called on hitting the Back Button (or even calling History.back())

[AM]

Hi,
I am running into this weird issue where the onHistoryChanged() isn't
being called when I hit the browser's back button or even if I call
History.back(). I am testing this in the hosted mode (even running it
in firefox yields me the same result). The strange thing is, if I call
History.back() thrice - looks like it calls onHistoryChanged() on the
third request - it is quite confusing and I was hoping if someone
could shed some light on this issue that I am running into.

I am using GWT 1.5 and to demonstrate my case, I'll use the example in
the GWT-1.5 tutorial (http://preview.tinyurl.com/6grjh2)

// Excluding imports for brevity

// Entry point classes define <code>onModuleLoad()</code>.
public class BrowserHistoryExample implements EntryPoint {

  TabPanel tabPanel;

  public void onModuleLoad() {

    tabPanel = new TabPanel();

    int tabIndex = 0;

    // A Ext-GWT ContentPanel
(com.extjs.gxt.ui.client.widget.ContentPanel)
    ContentPanel cp = new ContentPanel();
    cp.addText("Page1");
    tabPanel.add(cp, "Page1");

    cp = new ContentPanel();
    cp.addText("Page2");
    tabPanel.add(cp, "Page2");

    Button backButton = new Button("Back");
    backButton.addClickListener(new ClickListener () {

                public void onClick(Widget arg0) {
                    System.out.println("Going back now ...");

                    History.back();

                    // Commenting this for now ...
                    // but on un-commenting, the third call to
History.back() seems to invoke onHistoryChanged()
                    // History.back();
                    // History.back();
                }
    });
    cp = new ContentPanel();
    cp.addText("Page3");
    cp.add(backButton);
    tabPanel.add(cp, "Page3");


    tabPanel.addTabListener(new TabListener() {

      public boolean onBeforeTabSelected(SourcesTabEvents sender, int
tabIndex) {
        return true;
      }

      public void onTabSelected(SourcesTabEvents sender, int tabIndex)
{
          // Push an item onto the history stack
          System.out.println("Pushing tabIndex: " + tabIndex + " on the
stack");
          History.newItem("page" + tabIndex);
      }
    });

    History.addHistoryListener(new HistoryListener() {

      public void onHistoryChanged(String historyToken) {

          System.out.println("Got token: " + historyToken);

        // Parse the history token
        try {
          if (historyToken.substring(0, 4).equals("page")) {
            String tabIndexToken = historyToken.substring(4, 5);
            int tabIndex = Integer.parseInt(tabIndexToken);
            // Select the specified tab panel
            tabPanel.selectTab(tabIndex);
          } else {
            tabPanel.selectTab(0);
          }

        } catch (IndexOutOfBoundsException e) {
          tabPanel.selectTab(0);
        }
      }
    });

    tabPanel.selectTab(0);
    RootPanel.get().add(tabPanel);
  }
}

So the thing is, when I navigate from Page1 tab to Page2 tab to Page3
tab - and then when I hit the "back" button (defined above, which
simply calls History.back()) - nothing really happens for the first 2
times I hit the button. Only when I hit it the third time (or
alternatively call History.back() thrice in the buttonClick event) -
is the onHistoryChanged() method invoked.

Again, it would be great if someone could help me figure out whats
going on?

Thanks!

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