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// Copyright 2008 The Closure Library Authors. All Rights Reserved.
//
// 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.
/**
* @fileoverview This event handler will dispatch events when
* {@code navigator.onLine} changes. HTML5 defines two events, online and
* offline that is fired on the window. As of today 3 browsers support these
* events: Firefox 3 (Gecko 1.9), Opera 9.5, and IE8. If we have any of these
* we listen to the 'online' and 'offline' events on the current window
* object. Otherwise we poll the navigator.onLine property to detect changes.
*
* Note that this class only reflects what the browser tells us and this usually
* only reflects changes to the File -> Work Offline menu item.
*
* @author arv@google.com (Erik Arvidsson)
* @see ../demos/onlinehandler.html
*/
// TODO(arv): We should probably implement some kind of polling service and/or
// a poll for changes event handler that can be used to fire events when a state
// changes.
goog.provide('goog.events.OnlineHandler');
goog.provide('goog.events.OnlineHandler.EventType');
goog.require('goog.Timer');
goog.require('goog.events.BrowserFeature');
goog.require('goog.events.EventHandler');
goog.require('goog.events.EventTarget');
goog.require('goog.userAgent');
/**
* Basic object for detecting whether the online state changes.
* @constructor
* @extends {goog.events.EventTarget}
*/
goog.events.OnlineHandler = function() {
goog.events.EventTarget.call(this);
this.eventHandler_ = new goog.events.EventHandler(this);
// Some browsers do not support navigator.onLine and therefore we don't
// bother setting up events or timers.
if (!goog.events.BrowserFeature.HAS_NAVIGATOR_ONLINE_PROPERTY) {
return;
}
if (goog.events.BrowserFeature.HAS_HTML5_NETWORK_EVENT_SUPPORT) {
var target =
goog.events.BrowserFeature.HTML5_NETWORK_EVENTS_FIRE_ON_BODY ?
document.body : window;
this.eventHandler_.listen(target, ['online', 'offline'],
this.handleChange_);
} else {
this.online_ = this.isOnline();
this.timer_ = new goog.Timer(goog.events.OnlineHandler.POLL_INTERVAL_);
this.eventHandler_.listen(this.timer_, goog.Timer.TICK, this.handleTick_);
this.timer_.start();
}
};
goog.inherits(goog.events.OnlineHandler, goog.events.EventTarget);
/**
* Enum for the events dispatched by the OnlineHandler.
* @enum {string}
*/
goog.events.OnlineHandler.EventType = {
ONLINE: 'online',
OFFLINE: 'offline'
};
/**
* The time to wait before checking the {@code navigator.onLine} again.
* @type {number}
* @private
*/
goog.events.OnlineHandler.POLL_INTERVAL_ = 250;
/**
* Stores the last value of the online state so we can detect if this has
* changed.
* @type {boolean}
* @private
*/
goog.events.OnlineHandler.prototype.online_;
/**
* The timer object used to poll the online state.
* @type {goog.Timer}
* @private
*/
goog.events.OnlineHandler.prototype.timer_;
/**
* Event handler to simplify event listening.
* @type {goog.events.EventHandler}
* @private
*/
goog.events.OnlineHandler.prototype.eventHandler_;
/**
* Returns whether or not the system is online. This method works properly
* regardless of whether or not the listener IsListening.
* @return {boolean} Whether the browser is currently thinking it is online.
*/
goog.events.OnlineHandler.prototype.isOnline = function() {
return goog.events.BrowserFeature.HAS_NAVIGATOR_ONLINE_PROPERTY ?
navigator.onLine : true;
};
/**
* Called every time the timer ticks to see if the state has changed and when
* the online state changes the method handleChange_ is called.
* @param {goog.events.Event} e The event object.
* @private
*/
goog.events.OnlineHandler.prototype.handleTick_ = function(e) {
var online = this.isOnline();
if (online != this.online_) {
this.online_ = online;
this.handleChange_(e);
}
};
/**
* Called when the online state changes. This dispatches the
* {@code ONLINE} and {@code OFFLINE} events respectively.
* @param {goog.events.Event} e The event object.
* @private
*/
goog.events.OnlineHandler.prototype.handleChange_ = function(e) {
var type = this.isOnline() ?
goog.events.OnlineHandler.EventType.ONLINE :
goog.events.OnlineHandler.EventType.OFFLINE;
this.dispatchEvent(type);
};
/** @override */
goog.events.OnlineHandler.prototype.disposeInternal = function() {
goog.events.OnlineHandler.superClass_.disposeInternal.call(this);
this.eventHandler_.dispose();
delete this.eventHandler_;
if (this.timer_) {
this.timer_.dispose();
delete this.timer_;
}
};
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