Firefox扩展学习笔记(3) -- 更精确的页面控制以及xmlhttpRequest

今天学习的一点代码：

首先使用 Process Listener 接口可以跟踪一个页面（tab页）加载、完成加载、切换时候的状态。以下代码在tab页加载完成时，以及切换tab页的时候会触发自定义的函数

然后是在XPCOM中使用xmlhttprequest，和一般js里不同的是，需要调用一个组件类然后创建一个实例:
Components.classes["@mozilla.org/xmlextras/xmlhttprequest;1"] 
                       .createInstance(Components.interfaces.nsIXMLHttpRequest); 

不过这里的XHR一样要受到同源策略的限制。不知道GreaseMonkey的 GM_xmlhttpRequest 是怎么实现的，继续学习中。

整个例子核心代码如下：

const STATE_START = Components.interfaces.nsIWebProgressListener.STATE_START;
const STATE_STOP = Components.interfaces.nsIWebProgressListener.STATE_STOP;

var myListener =
{
QueryInterface: function(aIID)
{
if (aIID.equals(Components.interfaces.nsIWebProgressListener) ||
aIID.equals(Components.interfaces.nsISupportsWeakReference) ||
aIID.equals(Components.interfaces.nsISupports))
return this;
throw Components.results.NS_NOINTERFACE;
},

onStateChange: function(aWebProgress, aRequest, aFlag, aStatus)
{
// If you use myListener for more than one tab/window, use
// aWebProgress.DOMWindow to obtain the tab/window which triggers the state change
if(aFlag & STATE_START)
{
// This fires when the load event is initiated
//alert("start");
}
if(aFlag & STATE_STOP)
{
// This fires when the load finishes
//alert("stop");
myExtension.doSomething(aWebProgress);
}
return 0;
},

onLocationChange: function(aProgress, aRequest, aURI)
{
// This fires when the location bar changes; i.e load event is confirmed
// or when the user switches tabs. If you use myListener for more than one tab/window,
// use aProgress.DOMWindow to obtain the tab/window which triggered the change.

myExtension.doSomething(aProgress);
return 0;
},

// For definitions of the remaining functions see XULPlanet.com
onProgressChange: function() {return 0;},
onStatusChange: function() {return 0;},
onSecurityChange: function() {return 0;},
onLinkIconAvailable: function() {return 0;}
}

var i; // counter

var scriptText = {
src: '',
textContent: ''
};


var myExtension = {
init: function() {
// Listen for webpage loads
gBrowser.addProgressListener(myListener,
Components.interfaces.nsIWebProgress.NOTIFY_STATE_DOCUMENT);
},

uninit: function() {
gBrowser.removeProgressListener(myListener);
},

doSomething: function(aProgress) {
var doc = aProgress.DOMWindow.document;

for (i=0; i
scriptText.src = doc.getElementsByTagName("script")[i].src;
scriptText.textContent = doc.getElementsByTagName("script")[i].textContent;
if (scriptText.src == ""){
//scriptText.textContent = doc.getElementsByTagName("script")[i].textContent;
//alert(scriptText.textContent);
}
else {
ajaxGet(scriptText.src);
//alert(scriptText.src+'\n\n'+scriptText.textContent);
}
}
}
};

window.addEventListener("load", function() {myExtension.init()}, false);
window.addEventListener("unload", function() {myExtension.uninit()}, false);


// XMLHttpRequest
function ajaxGet(url){
var req = Components.classes["@mozilla.org/xmlextras/xmlhttprequest;1"]
.createInstance(Components.interfaces.nsIXMLHttpRequest);
req.onprogress = onProgress;
req.onload = onLoad;
req.onerror = onError;
req.open("GET", url, true);
req.send(null);
}

function onProgress(e){

}

function onLoad(e){
dump(e.target.status+'\n\n'+e.target.responseText);
}

function onError(e){

}