com.google.gwt.activity.shared
Class ActivityManager

java.lang.Object
  com.google.gwt.activity.shared.ActivityManager

All Implemented Interfaces:

EventHandler, PlaceChangeEvent.Handler, PlaceChangeRequestEvent.Handler

public class ActivityManager
extends java.lang.Object
implements PlaceChangeEvent.Handler, PlaceChangeRequestEvent.Handler

Manages Activity objects that should be kicked off in response to PlaceChangeEvent events. Each activity can start itself asynchronously, and provides a widget to be shown when it's ready to run.

ActivityManager

public ActivityManager(ActivityMapper mapper,
                       EventBus eventBus)

Create an ActivityManager. Next call setDisplay(com.google.gwt.user.client.ui.AcceptsOneWidget).

Parameters:

mapper - finds the Activity for a given Place

eventBus - source of PlaceChangeEvent and PlaceChangeRequestEvent events.

getActiveEventBus

public EventBus getActiveEventBus()

Returns an event bus which is in use by the currently running activity.

Any handlers attached to the returned event bus will be de-registered when the current activity is stopped.

Returns:

the event bus used by the current activity

onPlaceChange

public void onPlaceChange(PlaceChangeEvent event)

Deactivate the current activity, find the next one from our ActivityMapper, and start it.

The current activity's widget will be hidden immediately, which can cause flicker if the next activity provides its widget asynchronously. That can be minimized by decent caching. Perenially slow activities might mitigate this by providing a widget immediately, with some kind of "loading" treatment.

Specified by:

onPlaceChange in interface PlaceChangeEvent.Handler

Parameters:

event - the PlaceChangeEvent

onPlaceChangeRequest

public void onPlaceChangeRequest(PlaceChangeRequestEvent event)

Reject the place change if the current activity is not willing to stop.

Specified by:

onPlaceChangeRequest in interface PlaceChangeRequestEvent.Handler

Parameters:

event - the PlaceChangeRequestEvent

See Also:

PlaceChangeRequestEvent.Handler.onPlaceChangeRequest(PlaceChangeRequestEvent)

setDisplay

public void setDisplay(AcceptsOneWidget display)

Sets the display for the receiver, and has the side effect of starting or stopping its monitoring the event bus for place change events.

If you are disposing of an ActivityManager, it is important to call setDisplay(null) to get it to deregister from the event bus, so that it can be garbage collected.

Parameters:

display - an instance of AcceptsOneWidget