com.sfeir.common.gwt.client.mvp.PlaceController.java Source code

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Here is the source code for com.sfeir.common.gwt.client.mvp.PlaceController.java

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/*
 * Copyright 2010 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.sfeir.common.gwt.client.mvp;

import java.util.logging.Logger;

import com.google.gwt.core.client.GWT;
import com.google.gwt.place.shared.Place;
import com.google.gwt.place.shared.PlaceChangeEvent;
import com.google.gwt.place.shared.PlaceChangeRequestEvent;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.Window.ClosingEvent;
import com.google.gwt.user.client.Window.ClosingHandler;
import com.google.web.bindery.event.shared.EventBus;
import com.sfeir.common.gwt.client.events.ReplacePlaceEvent;

/**
 * In charge of the user's location in the app.
 */
public class PlaceController extends com.google.gwt.place.shared.PlaceController {

    private static final Logger log = Logger.getLogger(PlaceController.class.getName());

    private final EventBus eventBus;

    private final Delegate delegate;
    private Place where = Place.NOWHERE;

    /**
     * Create a new PlaceController with a {@link DefaultDelegate}. The
     * DefaultDelegate is created via a call to GWT.create(), so an alternative
     * default implementation can be provided through <replace-with> rules
     * in a {@code .gwt.xml} file.
     * 
     * @param eventBus the {@link EventBus}
     */
    public PlaceController(EventBus eventBus) {
        this(eventBus, (Delegate) GWT.create(DefaultDelegate.class));
    }

    /**
     * Create a new PlaceController.
     * 
     * @param eventBus the {@link EventBus}
     * @param delegate the {@link Delegate} in charge of Window-related events
     */
    public PlaceController(EventBus eventBus, Delegate delegate) {
        super(eventBus);
        this.eventBus = eventBus;
        this.delegate = delegate;
        delegate.addWindowClosingHandler(new ClosingHandler() {
            public void onWindowClosing(ClosingEvent event) {
                String warning = maybeGoTo(Place.NOWHERE);
                if (warning != null) {
                    event.setMessage(warning);
                }
            }
        });
    }

    /**
     * Returns the current place.
     * 
     * @return a {@link Place} instance
     */
    public Place getWhere() {
        return where;
    }

    /**
     * Request a change to a new place. It is not a given that we'll actually get
     * there. First a {@link PlaceChangeRequestEvent} will be posted to the event
     * bus. If any receivers post a warning message to that event, it will be
     * presented to the user via {@link Delegate#confirm(String)} (which is
     * typically a call to {@link Window#confirm(String)}). If she cancels, the
     * current location will not change. Otherwise, the location changes and a
     * {@link PlaceChangeEvent} is posted announcing the new place.
     * 
     * @param newPlace a {@link Place} instance
     */
    public void goTo(Place newPlace) {
        log.fine("goTo: " + newPlace);

        if (getWhere().equals(newPlace)) {
            log.fine("Asked to return to the same place: " + newPlace);
            return;
        }

        String warning = maybeGoTo(newPlace);
        if (warning == null || delegate.confirm(warning)) {
            where = newPlace;
            eventBus.fireEvent(new PlaceChangeEvent(newPlace));
        }
    }

    /**
     * Request a replace to the current place. It is not a given that we'll actually get
     * there. First a {@link PlaceChangeRequestEvent} will be posted to the event
     * bus. If any receivers post a warning message to that event, it will be
     * presented to the user via {@link Delegate#confirm(String)} (which is
     * typically a call to {@link Window#confirm(String)}). If she cancels, the
     * current location will not change. Otherwise, the location changes and a
     * {@link PlaceChangeEvent} is posted announcing the new place.
     * 
     * @param newPlace a {@link Place} instance
     */
    public void replace(Place newPlace) {
        where = newPlace;
        eventBus.fireEvent(new ReplacePlaceEvent(newPlace));
    }

    /**
     * 
     * @param newPlace The new place you want to goto
     * @return null if there are no problems to go to the new Place or the message instead
     */
    public String maybeGoTo(Place newPlace) {
        PlaceChangeRequestEvent willChange = new PlaceChangeRequestEvent(newPlace);
        eventBus.fireEvent(willChange);
        String warning = willChange.getWarning();
        return warning;
    }
}