_common.js

这是一个ajax的例子大家好好的看看就是一个鱼眼的效果

		this._cacheDojoResources();
		
		// FIXME: need to pull in the firebug lite files here!
		// workaround or else we will get an error on page load
		// from Dojo that it can't find 'console.debug' for optimized builds
		// dojox.off.files.cache(dojo.config.baseRelativePath + "src/debug.js");
		
		// make sure that resources needed by all of our underlying
		// Dojo Storage storage providers will be available
		// offline
		dojox.off.files.cache(dojox.storage.manager.getResourceList());
		
		// slurp the page if the end-developer wants that
		dojox.off.files._slurp();
		
		// see if we have an offline cache; when done, move
		// on to the rest of our startup tasks
		this._checkOfflineCacheAvailable(dojo.hitch(this, "_onOfflineCacheChecked"));
	},
	
	_onOfflineCacheChecked: function(){
		// this method is part of our _onLoad series of startup tasks
		
		// if we have an offline cache, see if we have been added to the 
		// list of available offline web apps yet
		if(this.hasOfflineCache && this.enabled){
			// load framework data; when we are finished, continue
			// initializing ourselves
			this._load(dojo.hitch(this, "_finishStartingUp"));
		}else if(this.hasOfflineCache && !this.enabled){
			// we have an offline cache, but it is disabled for some reason
			// perhaps due to the user denying a core operation
			this._finishStartingUp();
		}else{
			this._keepCheckingUntilInstalled();
		}
	},
	
	_keepCheckingUntilInstalled: function(){
		// this method is part of our _onLoad series of startup tasks
		
		// kick off a background interval that keeps
		// checking to see if an offline cache has been
		// installed since this page loaded
			
		// FIXME: Gears: See if we are installed somehow after the
		// page has been loaded
		
		// now continue starting up
		this._finishStartingUp();
	},
	
	_finishStartingUp: function(){
		//console.debug("dojox.off._finishStartingUp");
		
		// this method is part of our _onLoad series of startup tasks
		
		if(!this.hasOfflineCache){
			this.onLoad();
		}else if(this.enabled){
			// kick off a thread to check network status on
			// a regular basis
			this._startNetworkThread();

			// try to go online
			this.goOnline(dojo.hitch(this, function(){
				//console.debug("Finished trying to go online");
				// indicate we are ready to be used
				dojox.off.onLoad();
			}));
		}else{ // we are disabled or a core operation failed
			if(this.coreOpFailed){
				this.onFrameworkEvent("coreOperationFailed");
			}else{
				this.onLoad();
			}
		}
	},
	
	_onPageLoad: function(){
		//console.debug("dojox.off._onPageLoad");
		this._pageLoaded = true;
		
		if(this._storageLoaded && this._initializeCalled){
			this._onLoad();
		}
	},
	
	_onStorageLoad: function(){
		//console.debug("dojox.off._onStorageLoad");
		this._storageLoaded = true;
		
		// were we able to initialize storage? if
		// not, then this is a core operation, and
		// let's indicate we will need to fail fast
		if(!dojox.storage.manager.isAvailable()
			&& dojox.storage.manager.isInitialized()){
			this.coreOpFailed = true;
			this.enabled = false;
		}
		
		if(this._pageLoaded && this._initializeCalled){
			this._onLoad();		
		}
	},
	
	_isSiteAvailable: function(callback){
		// summary:
		//		Determines if our web application's website is available.
		// description:
		//		This method will asychronously determine if our web
		//		application's web site is available, which is a good proxy for
		//		network availability. The URL dojox.off.availabilityURL is
		//		used, which defaults to this site's domain name (ex:
		//		foobar.com). We check for dojox.off.AVAILABILITY_TIMEOUT (in
		//		seconds) and abort after that
		// callback: Function
		//		An optional callback function that will receive one argument:
		//		whether the site is available or not and is boolean. If this
		//		function is not present we call dojox.off.onNetwork instead if we
		//		are able to go online.
		dojo.xhrGet({
			url:		this._getAvailabilityURL(),
			handleAs:	"text",
			timeout:	this.NET_CHECK * 1000, 
			error:		dojo.hitch(this, function(err){
				//console.debug("dojox.off._isSiteAvailable.error: " + err);
				this.goingOnline = false;
				this.isOnline = false;
				if(callback){ callback(false); }
			}),
			load:		dojo.hitch(this, function(data){
				//console.debug("dojox.off._isSiteAvailable.load, data="+data);
				this.goingOnline = false;
				this.isOnline = true;
				
				if(callback){ callback(true);
				}else{ this.onNetwork("online"); }
			})
		});
	},
	
	_startNetworkThread: function(){
		//console.debug("startNetworkThread");
		
		// kick off a thread that does periodic
		// checks on the status of the network
		if(!this.doNetChecking){
			return;
		}
		
		window.setInterval(dojo.hitch(this, function(){	
			var d = dojo.xhrGet({
				url:	 	this._getAvailabilityURL(),
				handleAs:	"text",
				timeout: 	this.NET_CHECK * 1000,
				error:		dojo.hitch(this, 
								function(err){
									if(this.isOnline){
										this.isOnline = false;
										
										// FIXME: xhrGet() is not
										// correctly calling abort
										// on the XHR object when
										// it times out; fix inside
										// there instead of externally
										// here
										try{
											if(typeof d.ioArgs.xhr.abort == "function"){
												d.ioArgs.xhr.abort();
											}
										}catch(e){}
					
										// if things fell in the middle of syncing, 
										// stop syncing
										dojox.off.sync.isSyncing = false;
					
										this.onNetwork("offline");
									}
								}
							),
				load:		dojo.hitch(this, 
								function(data){
									if(!this.isOnline){
										this.isOnline = true;
										this.onNetwork("online");
									}
								}
							)
			});

		}), this.NET_CHECK * 1000);
	},
	
	_getAvailabilityURL: function(){
		var url = this.availabilityURL.toString();
		
		// bust the browser's cache to make sure we are really talking to
		// the server
		if(url.indexOf("?") == -1){
			url += "?";
		}else{
			url += "&";
		}
		url += "browserbust=" + new Date().getTime();
		
		return url;
	},
	
	_onOfflineCacheInstalled: function(){
		this.onFrameworkEvent("offlineCacheInstalled");
	},
	
	_cacheDojoResources: function(){
		// if we are a non-optimized build, then the core Dojo bootstrap
		// system was loaded as separate JavaScript files;
		// add these to our offline cache list. these are
		// loaded before the dojo.require() system exists
		
		// FIXME: create a better mechanism in the Dojo core to
		// expose whether you are dealing with an optimized build;
		// right now we just scan the SCRIPT tags attached to this
		// page and see if there is one for _base/_loader/bootstrap.js
		var isOptimizedBuild = true;
		dojo.forEach(dojo.query("script"), function(i){
			var src = i.getAttribute("src");
			if(!src){ return; }
			
			if(src.indexOf("_base/_loader/bootstrap.js") != -1){
				isOptimizedBuild = false;
			}
		});
		
		if(!isOptimizedBuild){
			dojox.off.files.cache(dojo.moduleUrl("dojo", "_base.js").uri);
			dojox.off.files.cache(dojo.moduleUrl("dojo", "_base/_loader/loader.js").uri);
			dojox.off.files.cache(dojo.moduleUrl("dojo", "_base/_loader/bootstrap.js").uri);
			
			// FIXME: pull in the host environment file in a more generic way
			// for other host environments
			dojox.off.files.cache(dojo.moduleUrl("dojo", "_base/_loader/hostenv_browser.js").uri);
		}
		
		// add anything that was brought in with a 
		// dojo.require() that resulted in a JavaScript
		// URL being fetched
		
		// FIXME: modify dojo/_base/_loader/loader.js to
		// expose a public API to get this information
	
		for(var i = 0; i < dojo._loadedUrls.length; i++){
			dojox.off.files.cache(dojo._loadedUrls[i]);
		}
		
		// FIXME: add the standard Dojo CSS file
	},
	
	_save: function(){
		// summary:
		//		Causes the Dojo Offline framework to save its configuration
		//		data into local storage.	
	},
	
	_load: function(callback){
		// summary:
		//		Causes the Dojo Offline framework to load its configuration
		//		data from local storage
		dojox.off.sync._load(callback);
	}
});


// wait until the storage system is finished loading
dojox.storage.manager.addOnLoad(dojo.hitch(dojox.off, "_onStorageLoad"));

// wait until the page is finished loading
dojo.addOnLoad(dojox.off, "_onPageLoad");

}