Using the event bus may help there.
http://code.google.com/events/io/2009/sessions/GoogleWebToolkitBestPractices.html
and the two articles
http://code.google.com/webtoolkit/articles/mvp-architecture.html
On Jun 15, 9:14 am, ping2ravi <ping2r...@gmail.com> wrote:
> Hi Guys,
> I have just implemented a multipage(basically multi url) website using
> History. It works great using history token. But i need something else
> from GWT which i am not able to solve.
> Now when user clicks on something(link/button etc) i add the token to
> History and my history callbacks get called.
> Now in history value change handler i do something like this
>
> 1) FInd out what page need to be dispalyed(basically identify the
> panels etc).
> 2) now each of my panel which can have history implementing
> hasHistory(my own) interface, which has function
> recoverPanelFromHistory.
> 3) In this function, i check if i have client side data cahced for
> this panel, if yes then load it into panel and display it(basically
> add to main panel widget tree).
> 4) But if no cache data found then go to server and get data.
>
> one such implementation
> @Override
> public boolean recoverPanelFromHistory(Map<String, String>
> historyTokens) {
> String page = historyTokens.get(PAGE_PARAM);
> boolean returnValue = false;
> if("home".equalsIgnoreCase(page))
> {
> returnValue =
> userHomePanel.recoverPanelFromHistory(historyTokens); //and this
> function will calls its child panels if they support history
> if(returnValue )
> {
> mainContentPanel.clear(); //clearing the
> mainPanel view of client
> mainContentPanel.add(userHomePanel); //and
> adding the view
> according to history token value
> }
> else
> {
> //dont change the browser view and stay at
> current panel/view/page. This also means child panel can not be
> recovered and there must be some problem with history tokens provided.
> }
>
> }
> if("profile".equalsIgnoreCase(page))
> {
> returnValue =
> prodilePanel.recoverPanelFromHistory(historyTokens); //and this
> function will calls its child panels if they support history
> if(returnValue )
> {
> mainContentPanel.clear(); //clearing the
> mainPanel view of client
> mainContentPanel.add(profilePanel); //and
> adding the view
> according to history token value
> }
> else
> {
> //dont change the browser view and stay at
> current panel/view/page. This also means child panel can not be
> recovered and there must be some problem with history tokens provided.
> }
>
> }
> return returnValue;
>
> }
>
> So till now theoretically it sounds good and works good.
>
> Problem starts when lets say user lost his Internet connection or call
> fail at server because of any system level error..
>
> userHomePanel.recoverPanelFromHistory(historyTokens);
>
> This function does following things.
> 1) get the data from cache for this panel
> 2) if found call loadDataIntoPanel(data) function and load it into
> panel and return true.
> 3) else call the server to get data.
> Now server call is async and I need to return some value from
> userHomePanel.recoverPanelFromHistory(historyTokens);, so if i return
> true and call fails at server because of some network problem then
> ideally i dont want to switch to new view as per this history action
> but my function has already returned true and mainPanle has already
> changed the view to new panel.
> Now i dont want child panels to call parentPanel's method to tell them
> later that server call was success or failure so that main parent
> panel can decide whethere i should switch panels/view or not. If child
> need to know parent then my all panels will be too much dependent on
> each other and they will be too much crossed chain to each other.
>
> If you see gmail it uses such features. If you have loaded ur inbox
> and then you lost ur internet connection and then u click on any
> email. Then gmail doesnt take you to single mail viewer page and then
> tell "oh u lost ur connection" but it just keep you on inbox view and
> keep trying and after some time stop trying.
>
> How can i achieve such functionality.?
> Are there any existing libraries to do that or any particular design
> pattern is there?
>
> Thanks, in advance
>
> Ravi.
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