Java tutorial
/* * 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.gwt.geolocation.client; import com.google.gwt.core.client.Callback; import com.google.gwt.core.client.GWT; import com.google.gwt.core.client.JavaScriptObject; import com.google.gwt.dom.client.PartialSupport; /** * Implements the HTML5 Geolocation interface. * * <p> * You can obtain a user's position by first calling * <code>Geolocation.getIfSupported()</code> * </p> * * <p> * Once you have a <code>Geolocation</code>, you can request the user's current * position by calling {@link #getCurrentPosition(Callback)} or * {@link #watchPosition(Callback)}. * </p> * * <p> * The first time an application requests the user's position, the browser will * prompt the user for permission. If the user grants permission, the browser * will locate the user and report it back to your application. If the user * declines permission, the callback's {@link Callback#onFailure(Object)} method * will be called with a {@link PositionError} with its code set to * {@link PositionError#PERMISSION_DENIED}. * </p> * * <p> * <span style="color:red;">Experimental API: This API is still under * development and is subject to change.</span> * * <p> * This may not be supported on all browsers. * </p> * * @see <a href="http://www.w3.org/TR/geolocation-API/">W3C Geolocation API</a> * @see <a href="http://diveintohtml5.org/geolocation.html">Dive Into HTML5 - * Geolocation</a> */ @PartialSupport public class Geolocation { private static GeolocationSupportDetector detector; private static Geolocation impl; /** * Detector for browser support for Geolocation. */ private static class GeolocationSupportDetector { private static native boolean detectSupport() /*-{ return !!$wnd.navigator.geolocation; }-*/; private boolean supported = detectSupport(); public boolean isSupported() { return supported; } } /** * Detector for browsers that do not support Geolocation. */ @SuppressWarnings("unused") private static class GeolocationSupportDetectorNo extends GeolocationSupportDetector { @Override public boolean isSupported() { return false; } } /** * Additional options for receiving the user's location. */ public static class PositionOptions { private boolean enableHighAccuracy = false; private int timeout = -1; private int maximumAge = 0; /** * Sets whether or not the application will request a more accurate position * from the browser. * * <p> * If the browser supports this option, the user will be prompted to grant * permission to this application, even if permission to get the user's * (less accurate) position has already been granted.</p> * * <p> * Requesting high accuracy may be slower, or not supported at all, * depending on the browser. * </p> * * <p> * By default this is <code>false</code> * </p> */ public PositionOptions setHighAccuracyEnabled(boolean enabled) { this.enableHighAccuracy = enabled; return this; } /** * Allows the browser to return a position immediately with a cached * position. The maximum age is then the oldest acceptable cached * position. If no acceptable cached position is found, the browser will * locate the user and cache and return the position. * * <p> * By default this is 0, which means that the position cache will not be * used. * </p> */ public PositionOptions setMaximumAge(int maximumAge) { this.maximumAge = maximumAge; return this; } /** * Sets the amount of time (in milliseconds) that the application is willing * to wait before getting the user's position. If a request for position * takes more than this amount of time, an error will result. * * <p> * By default this is -1, which means there is no application-specified * timeout. * </p> */ public PositionOptions setTimeout(int timeout) { this.timeout = timeout; return this; } } /** * Returns a {@link Geolocation} if the browser supports this feature, and * <code>null</code> otherwise. */ public static Geolocation getIfSupported() { if (!isSupported()) { return null; } else { if (impl == null) { impl = new Geolocation(); } return impl; } } /** * Returns <code>true</code> if the browser supports geolocation. */ public static boolean isSupported() { if (detector == null) { detector = GWT.create(GeolocationSupportDetector.class); } return detector.isSupported(); } private static void handleFailure(Callback<Position, PositionError> callback, int code, String msg) { callback.onFailure(new PositionError(code, msg)); } private static void handleSuccess(Callback<Position, PositionError> callback, PositionImpl pos) { callback.onSuccess(pos); } private static native JavaScriptObject toJso(PositionOptions options) /*-{ var opt = {}; if (options) { opt.enableHighAccuracy = options.@com.google.gwt.geolocation.client.Geolocation.PositionOptions::enableHighAccuracy; opt.maximumAge = options.@com.google.gwt.geolocation.client.Geolocation.PositionOptions::maximumAge; if (options.@com.google.gwt.geolocation.client.Geolocation.PositionOptions::timeout > 0) { opt.timeout = options.@com.google.gwt.geolocation.client.Geolocation.PositionOptions::timeout; } } return opt; }-*/; /** * Should be instantiated by {@link #getIfSupported()}. */ protected Geolocation() { } /** * Stops watching the user's position. * * @param watchId the ID of a position watch as returned by a previous call to * {@link #watchPosition(Callback)}. */ public native void clearWatch(int watchId) /*-{ $wnd.navigator.geolocation.clearWatch(watchId); }-*/; /** * Calls the callback with the user's current position. */ public void getCurrentPosition(Callback<Position, PositionError> callback) { getCurrentPosition(callback, null); } /** * Calls the callback with the user's current position, with additional * options. */ public native void getCurrentPosition(Callback<Position, PositionError> callback, PositionOptions options) /*-{ var opt = @com.google.gwt.geolocation.client.Geolocation::toJso(*)(options); var success = $entry(function(pos) { @com.google.gwt.geolocation.client.Geolocation::handleSuccess(*)(callback, pos); }); var failure = $entry(function(err) { @com.google.gwt.geolocation.client.Geolocation::handleFailure(*) (callback, err.code, err.message); }); if (@com.google.gwt.geolocation.client.Geolocation::isSupported()) { $wnd.navigator.geolocation.getCurrentPosition(success, failure, opt); } }-*/; /** * Repeatedly calls the given callback with the user's position, as it * changes. * * <p> * The frequency of these updates is entirely up to the browser. There is no * guarantee that updates will be received at any set interval, but are * instead designed to be sent when the user's position changes. This method * should be used instead of polling the user's current position. * </p> * * @return the ID of this watch, which can be passed to * {@link #clearWatch(int)} to stop watching the user's position. */ public int watchPosition(Callback<Position, PositionError> callback) { return watchPosition(callback, null); } /** * Repeatedly calls the given callback with the user's position, as it * changes, with additional options. * * <p> * The frequency of these updates is entirely up to the browser. There is no * guarantee that updates will be received at any set interval, but are * instead designed to be sent when the user's position changes. This method * should be used instead of polling the user's current position. * </p> * * <p> * If the browser does not support geolocation, this method will do nothing, * and will return -1. * </p> * * @return the ID of this watch, which can be passed to * {@link #clearWatch(int)} to stop watching the user's position. */ public native int watchPosition(Callback<Position, PositionError> callback, PositionOptions options) /*-{ var opt = @com.google.gwt.geolocation.client.Geolocation::toJso(*)(options); var success = $entry(function(pos) { @com.google.gwt.geolocation.client.Geolocation::handleSuccess(*)(callback, pos); }); var failure = $entry(function(err) { @com.google.gwt.geolocation.client.Geolocation::handleFailure(*) (callback, err.code, err.message); }); if (@com.google.gwt.geolocation.client.Geolocation::isSupported()) { $wnd.navigator.geolocation.watchPosition(success, failure, opt); } }-*/; }