Group items tagged

I think the overall idea of activities is that they are short-lived instances, so they're effectively "lazily created" (actually, a new instance is created each time one is needed) and they don't need to be "awoken" because if they're not currently in use they're already "dead" and garbage collected. The ActivityManager (actually its associated ActivityMapper) will decide whether a particular activity is needed (and then instantiate it, possibly going through a GWT.runAsync for code splitting); the activity will listen to events its interested in *during its lifetime* (e.g. whether some object has changed or has been added or deleted, so it can update its view); but when it's done (stopped or cancelled), it's simply thrown away (the event bus passed to the start() method is a ResettableEventBus so all handlers have been automatically unregistered for you, which as a side effect allows the activity to be garbage collected). This is the (AIUI) intended use, but nothing forces you to write such short-lived instances: you can very well use singletons, but then you'll have the additional task of maintaining state between "runs" (start/stop or start/cancel), in which case your activity can listen to events from the event bus after being stopped/cancelled (just use the "real" event bus instead of the ResettableEventBus passed to the start() method); but it won't "ask to be revealed": navigation is handled at another layer, triggered on the PlaceController and handled by ActivityManagers.

> is so called REST like URLs possible ? /employees/1 This is no more or less "REST like" than the above (I assure you!); and yes it's possible (the issues then are to identify objects that are not yet persisted to the server; and of course mapping the "employees" to an EntityProxy class, representing the class+id couple in the Place, and having dedicated "find" methods to retrieve the object from the server, as without an EntityProxyId you won't be able to use RequestFactory.find()) > does it mean we have to write custom getPlace, getToken, to convert > tokens to places ? Yes. That or writing your own PlaceHistoryMapper that won't use PlaceTokenizer's at all (i.e. implement PlaceHistoryMapper in a concrete class and not use the GWT.create() magic to generate the implementation).

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.

Activities are more tied to the concept of Places than of MVP, i.e. navigation and user experience rather than code structure ("developer experience").

I think the overall idea of activities is that they are short-lived instances, so they're effectively "lazily created" (actually, a new instance is created each time one is needed) and they don't need to be "awoken" because if they're not currently in use they're already "dead" and garbage collected. The ActivityManager (actually its associated ActivityMapper) will decide whether a particular activity is needed (and then instantiate it, possibly going through a GWT.runAsync for code splitting); the activity will listen to events its interested in *during its lifetime* (e.g. whether some object has changed or has been added or deleted, so it can update its view); but when it's done (stopped or cancelled), it's simply thrown away (the event bus passed to the start() method is a ResettableEventBus so all handlers have been automatically unregistered for you, which as a side effect allows the activity to be garbage collected). This is the (AIUI) intended use, but nothing forces you to write such short-lived instances: you can very well use singletons, but then you'll have the additional task of maintaining state between "runs" (start/stop or start/cancel), in which case your activity can listen to events from the event bus after being stopped/cancelled (just use the "real" event bus instead of the ResettableEventBus passed to the start() method); but it won't "ask to be revealed": navigation is handled at another layer, triggered on the PlaceController and handled by ActivityManagers.

your ChatBoxPresenter isn't related to a "place", i.e. it's "awoken" based on a "business event", not a navigation event; and in other words, it's not an Activity: case made. Activities (ActivityManager) is limited in scope to reacting to place changes and navigation (not that you couldn't use the Activity "contract" in other scenarios, such as your "chat box", but the ActivityManager wouldn't be the right tool for the job, you'd have to find/write another "activity manager" for your different use case). In other words: GWT 2.1 Activities won't replace GWTP as a whole (and I believe, as I already said in the past, that it's not its goal either).

Have a look at the Cell widgets' internals, they use MVP internally so the presenter can be tested independently from the views.