I'm finally starting to "get" GWT. At any time, a PlaceChangeEvent
can be fired on the app's EventBus
like so:
History.newItem("token-for-some-new-place");
This adds the event to the bus, whereby a registered ActivityManager
scoops it up and consults its internal ActivityMapper
to give it the Activity
associated with the PlaceChangeEvent
's Place
.
The Activity
(similar to a presenter or controller object from MVP/MVC) then obtains any data that is needed (via RPC calls to the server) and executes any business logic and configures the final view (typically a Composite
of some sort) to display.
As long as we're talking about a super-simple GWT app that only has one display region on its host page, then like I said, I "get" it.
Where I am choking now is what happens when you have an app that contains multiple display regions (areas that can be updated asynchronously from one another).
So I ask:
ActivityMapper
s supposed to be? Is there just one app-wide AppActivityMapper
that maps all Place
s to all Activity
ies, or should there be some sort of ActivityMapper
hierarchy/decomposition, where you have multiple mappers? (And if your answer to this is something along the lines of "this depends on the needs of your application" then please explain what requirements/needs drive the appropriate level of granularity!)Place
represents a URL token in your app (for the sake of making the Place
a bookmarkable state), then what happens when you have a more complex app that has multiple display regions (D1, D2, D3). How does one URL token (i.e. http://myapp.com/#token-for-some-new-place
) map to D1, D2 and D3? Wouldn't that mean ActivityMapper#getActivity
would have to be capable of returning a list of activities (List<Activity>
) whose start(AcceptsOneWidget, EventBus)
methods would all get callled?Thanks for any help here - code examples always rock.
A Place
represents, well, a place. It answers the existential questions of where did I come from?, where am I? and where am I going to?.
For a given place, the screen that's displayed to the user can be complex, and divided into a bunch of display regions. Each one is governed by an ActivityManager
, which asks an ActivityMapper
which Activity
to use for a given place, making everything loosely coupled (activities don't (have to) know where they're being used, for which place, which other activities are running concurrently, etc.)
So, you won't have a mapper that'd return a list of activities, but a list of mappers each returning one activity.
See: