Difference between revisions of "Examples/Eclipse Business Expense Reporting Tool/User State Service"

	protected void startUserContextServiceTracker() {
		userContextServiceTracker = new ServiceTracker(ExpenseReportingUI.getDefault().getContext(), IUserContextService.class.getName(), null) {
			/**
			 * We keep track of the first service we find and ignore the
			 * rest. This is a great example of where declarative services
			 * would be helpful: you can declare that you want exactly one
			 * instance of a service and that's what you get. 
			 */
			protected IUserContextService userContextService;
 
			/**
			 * This method is called when a matching service is found or
			 * added. This finds both pre-existing and new instances of the
			 * service.
			 */
			public Object addingService(ServiceReference reference) {
				Object service = super.addingService(reference);
				if (userContextService == null) {
					userContextService = (IUserContextService)service;
					/*
					 * Do the part where we get the user context in a
					 * syncExec block. This will make sure that it runs
					 * in the user interface thread for the current user.
					 * This doesn't matter too much on RCP/eRCP, but the
					 * thread that we're running in is pretty critical
					 * in RAP.
					 */
					syncExec(new Runnable() {
						public void run() {
							userContext = userContextService.getUserContext();
							connectToUserContext(userContext);
						}
					});
				}
				return service;
			}
 
			/**
			 * This method is called when the service is being removed, or the 
			 * tracker is being closed.
			 */
			public void removedService(ServiceReference reference, Object service) {
				if (service == userContextService) {
					disconnectFromUserContext(userContext);
					userContext = null;
					userContextService = null;
					// TODO Do we try to match up with a hypothetical second service in this case?
				}
				super.removedService(reference, service);
			};
 
 
		};
		userContextServiceTracker.open();
	}