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* I notice that you're injecting instances of your activities into your activity mapper. Activities are meant to be fairly lightweight objects, as opposed to the views that represent them, so they don't need to be singletons (which they effectively are since you have a single app with a single injected activity mapper). It's probably not necessarily a problem unless your activities have state associated with them (such as the entity that the user is currently working with), which you have to be careful to clear out between uses with different data. The same can be said about places.

My understanding is that you only want a single area of the shell to be managed by one ActivityManager. So if you have an entire shell/layout with more than one area that changes, let's say a main content area as well as a context menu (If I have MainAppPlace and SettingsAppPlace and OtherAppPlace both of which extend MainAppPlace, and you want to show a different context menu for Place of type SettingsAppPlace and places of type OtherAppPlace) I would just have main Shell that has a SimplePanel for content and Simplepanel for context_menu I just use an ActivityManager to control one spot of the main layout. is this not right? do you want your activitymanager controlling more than one area??

Views A key concept of MVP development is that a view is defined by an interface. This allows multiple view implementations based on client characteristics (such as mobile vs. desktop) and also facilitates lightweight unit testing by avoiding the time-consuming GWTTestCase. There is no View interface or class in GWT which views must implement or extend; however, GWT 2.1 introduces an IsWidget interface that is implemented by most Widgets as well as Composite. It is useful for views to extend IsWidget if they do in fact provide a Widget. Here is a simple view from our sample app. public interface GoodbyeView extends IsWidget {    void setName(String goodbyeName);} The corresponding implementation extends Composite, which keeps dependencies on a particular Widget from leaking out. public class GoodbyeViewImpl extends Composite implements GoodbyeView {    SimplePanel viewPanel = new SimplePanel();    Element nameSpan = DOM.createSpan();    public GoodbyeViewImpl() {        viewPanel.getElement().appendChild(nameSpan);        initWidget(viewPanel);    }    @Override    public void setName(String name) {        nameSpan.setInnerText("Good-bye, " + name);    }}

A place in GWT 2.1 is a Java object representing a particular state of the UI. A Place can be converted to and from a URL history token (see GWT's History object) by defining a PlaceTokenizer for each Place, and the PlaceHistoryHandler automatically updates the browser URL corresponding to each Place in your app.

Place

often your places are "parameterized", think of a detail/edit screen for example that needs the model's id. The token is a generic way to provide additional information (via the URL) to the place (i.e. the activity/-ies), i.e. "#editFoo:42". You can of course re-use one place to dispatch to several activities based on the token. See the (currently not used) for ProxyPlace and ProxyListPlace in the Expenses sample for an example.