ProxyListPlacePicker-template.java

package __TOP_LEVEL_PACKAGE__.client.scaffold.place;

import com.google.gwt.event.logical.shared.ValueChangeEvent;
import com.google.gwt.event.logical.shared.ValueChangeHandler;
import com.google.gwt.event.shared.EventBus;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.place.shared.PlaceChangeEvent;
import com.google.gwt.place.shared.PlaceController;
import com.google.gwt.user.client.ui.HasConstrainedValue;

/**
 * Drives a {@link ValueChangeHandler} populated with {@link ProxyListPlace}
 * instances, keeping it in sync with the {@link PlaceController}'s notion of
 * the current place, and firing place change events as selections are made.
 */
public class ProxyListPlacePicker implements ValueChangeHandler<ProxyListPlace>, PlaceChangeEvent.Handler {
	private HasConstrainedValue<ProxyListPlace> view;
	private final PlaceController placeController;
	private final ProxyPlaceToListPlace proxyPlaceToListPlace;

	public ProxyListPlacePicker(PlaceController placeController, ProxyPlaceToListPlace proxyPlaceToListPlace) {
		this.placeController = placeController;
		this.proxyPlaceToListPlace = proxyPlaceToListPlace;
	}

	public void onPlaceChange(PlaceChangeEvent event) {
		view.setValue(proxyPlaceToListPlace.proxyListPlaceFor(event.getNewPlace()), false);
	}

	public void onValueChange(ValueChangeEvent<ProxyListPlace> event) {
		placeController.goTo(event.getValue());
	}

	public HandlerRegistration register(EventBus eventBus, HasConstrainedValue<ProxyListPlace> view) {
		this.view = view;
		final HandlerRegistration placeRegistration = eventBus.addHandler(PlaceChangeEvent.TYPE, this);
		final HandlerRegistration viewRegistration = view.addValueChangeHandler(this);

		return new HandlerRegistration() {
			public void removeHandler() {
				placeRegistration.removeHandler();
				viewRegistration.removeHandler();
				ProxyListPlacePicker.this.view = null;
			}
		};
	}
}