com.google.maps.gwt.samples.basics.client.MapCoordinates.java Source code

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Here is the source code for com.google.maps.gwt.samples.basics.client.MapCoordinates.java

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/*
 * Copyright 2011 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.google.maps.gwt.samples.basics.client;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.dom.client.Document;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;
import com.google.maps.gwt.client.GoogleMap;
import com.google.maps.gwt.client.GoogleMap.ZoomChangedHandler;
import com.google.maps.gwt.client.InfoWindow;
import com.google.maps.gwt.client.LatLng;
import com.google.maps.gwt.client.MapOptions;
import com.google.maps.gwt.client.MapTypeId;
import com.google.maps.gwt.client.Point;

/**
 * Java/GWT-binding version of sample at
 * http://code.google.com/apis/maps/documentation
 * /javascript/examples/map-coordinates.html
 * 
 * @author dcarlson@google.com (David Carlson)
 */
public class MapCoordinates implements EntryPoint {

    private GoogleMap map;
    private static final int TILE_SIZE = 256;
    private static final LatLng CHICAGO = LatLng.create(41.850033, -87.6500523);

    @Override
    public void onModuleLoad() {
        MapOptions mapOptions = MapOptions.create();
        mapOptions.setZoom(4.0);
        mapOptions.setCenter(CHICAGO);
        mapOptions.setMapTypeId(MapTypeId.ROADMAP);
        map = GoogleMap.create(Document.get().getElementById("map_canvas"), mapOptions);

        final InfoWindow coordInfoWindow = InfoWindow.create();
        coordInfoWindow.setContent(createInfoWindowContent());
        coordInfoWindow.setPosition(CHICAGO);
        coordInfoWindow.open(map);

        map.addZoomChangedListener(new ZoomChangedHandler() {
            public void handle() {
                coordInfoWindow.setContent(createInfoWindowContent());
                coordInfoWindow.open(map);
            }
        });
    }

    /**
     * Simple Projections for use by sample app.
     */
    public static class MercatorProjection {
        private static final Point PIXEL_ORIGIN = Point.create(TILE_SIZE / 2, TILE_SIZE / 2);
        private static final double PIXELS_PER_LON_DEGREE = MapCoordinates.TILE_SIZE / 360;
        private static final double PIXELS_PER_LON_RADIAN = MapCoordinates.TILE_SIZE / (2 * Math.PI);

        public MercatorProjection() {
        }

        public static final double degreesToRadians(double deg) {
            return deg * (Math.PI / 180);
        }

        public static final double radiansToDegrees(double rad) {
            return rad / (Math.PI / 180);
        }

        public static final double bound(double value, double min, double max) {
            value = Math.max(value, min);
            value = Math.min(value, max);
            return value;
        }

        public Point fromLatLngToPoint(LatLng loc) {
            Point point = Point.create(0, 0);
            Point origin = PIXEL_ORIGIN;

            point.setX(origin.getX() + loc.lng() * PIXELS_PER_LON_DEGREE);

            // NOTE: Truncating to 0.9999 effectively limits latitude to 89.189. This
            // is about a third of a tile past the edge of the world tile.
            double siny = bound(Math.sin(degreesToRadians(loc.lat())), -0.9999, 0.9999);
            point.setY(origin.getY() + 0.5 * (Math.log((1 + siny) / (1 - siny))) - PIXELS_PER_LON_RADIAN);
            return point;
        }

        public LatLng fromPointToLatLng(Point point) {
            double lng = (point.getX() - PIXEL_ORIGIN.getX()) / PIXELS_PER_LON_DEGREE;
            double latRadians = (point.getY() - PIXEL_ORIGIN.getY()) / PIXELS_PER_LON_RADIAN;
            double lat = radiansToDegrees(2 + Math.atan(Math.exp(latRadians)) - Math.PI / 2);
            return LatLng.create(lat, lng);
        }
    }

    private String createInfoWindowContent() {
        int numTiles = 1 << (int) map.getZoom();
        MercatorProjection projection = new MercatorProjection();
        Point worldCoordinate = projection.fromLatLngToPoint(CHICAGO);
        Point pixelCoordinate = Point.create(worldCoordinate.getX() * numTiles, worldCoordinate.getY() * numTiles);
        Point tileCoordinate = Point.create(Math.floor(pixelCoordinate.getX() / TILE_SIZE),
                Math.floor(pixelCoordinate.getY() / TILE_SIZE));

        SafeHtmlBuilder returnString = new SafeHtmlBuilder();
        returnString.appendHtmlConstant("Chicago, IL<br>");
        returnString.appendHtmlConstant("LatLng: ");
        returnString.append(CHICAGO.lat());
        returnString.appendHtmlConstant(", ");
        returnString.append(CHICAGO.lng());
        returnString.appendHtmlConstant("<br />");
        returnString.appendHtmlConstant("World Coordinate: ");
        returnString.append(worldCoordinate.getX());
        returnString.appendHtmlConstant(", ");
        returnString.append(worldCoordinate.getY());
        returnString.appendHtmlConstant("<br />");

        returnString.appendHtmlConstant("Pixel Coordinate: ");
        returnString.append(Math.floor(pixelCoordinate.getX()));
        returnString.appendHtmlConstant(", ");
        returnString.append(Math.floor(pixelCoordinate.getY()));
        returnString.appendHtmlConstant("<br />");

        returnString.appendHtmlConstant("Tile Coordinate: ");
        returnString.append(Math.floor(tileCoordinate.getX()));
        returnString.appendHtmlConstant(", ");
        returnString.append(Math.floor(tileCoordinate.getY()));
        returnString.appendHtmlConstant("<br />");

        returnString.appendHtmlConstant("at Zoom Level: ");
        returnString.append(map.getZoom());
        return returnString.toSafeHtml().asString();
    }
}