为什么JavaScript函数会停止执行？

Question

我有以下JS函数，它是mozilla thunderbird扩展的第一个原型。 目标是连接到服务器并下载示例文件，然后解压缩并将内容存储在thunderbird配置文件文件夹中。 现在，这一切都正常工作，除了在文件系统上创建zip文件后，函数的执行停止。所以我必须重新启动这个函数，以便获得从zip文件中提取user.js文件的第二部分函数。 任何想法可能是什么问题？

function downloadFile(httpLoc) { 
    // get profile directory 
    var file = Components.classes["@mozilla.org/file/directory_service;1"]. 
     getService(Components.interfaces.nsIProperties). 
     get("ProfD", Components.interfaces.nsIFile); 

    var profilePath = file.path; 

    // change profile directory to native style 
    profilePath = profilePath.replace(/\\/gi , "\\\\"); 
    profilePath = profilePath.toLowerCase(); 

    // download the zip file 
    try { 
     //new obj_URI object 
     var obj_URI = Components.classes["@mozilla.org/network/io-service;1"].getService(Components.interfaces.nsIIOService).newURI(httpLoc, null, null); 

     //new file object 
     var obj_TargetFile = Components.classes["@mozilla.org/file/local;1"].createInstance(Components.interfaces.nsILocalFile); 

     //set to download the zip file into the profil direct 
     obj_TargetFile.initWithPath(profilePath + "\/" + "test.zip"); 

     //if file the zip file doesn't exist, create it 
     if(!obj_TargetFile.exists()) { 

      alert("zip file wird erstellt"); 

      obj_TargetFile.create(0x00,0644); 

     } 

     //new persitence object 
     var obj_Persist = Components.classes["@mozilla.org/embedding/browser/nsWebBrowserPersist;1"].createInstance(Components.interfaces.nsIWebBrowserPersist); 


     // with persist flags if desired ?? 
     const nsIWBP = Components.interfaces.nsIWebBrowserPersist; 
     const flags = nsIWBP.PERSIST_FLAGS_REPLACE_EXISTING_FILES; 
     obj_Persist.persistFlags = flags | nsIWBP.PERSIST_FLAGS_FROM_CACHE; 

     //save file to target 
     obj_Persist.saveURI(obj_URI,null,null,null,null,obj_TargetFile); 
    } catch (e) { 
     alert(e); 
    } finally { 
     // unzip the user.js file to the profile direc 

     // creat a zipReader, open the zip file 
     var zipReader = Components.classes["@mozilla.org/libjar/zip-reader;1"] 
      .createInstance(Components.interfaces.nsIZipReader); 

     zipReader.open(obj_TargetFile); 

     //new file object, thats where the user.js will be extracted 
     var obj_UnzipTarget = Components.classes["@mozilla.org/file/local;1"].createInstance(Components.interfaces.nsILocalFile); 

     //set path for the user.js 
     obj_UnzipTarget.initWithPath(profilePath + "\/" + "user.js"); 

     // if user.js doesn't exist, create it 
     if(!obj_UnzipTarget.exists()) { 
      alert("user.js wird erstellt"); 

      obj_UnzipTarget.create(0x00,0644); 
     } 

     // extract the user.js out of the zip file, to the specified path 
     zipReader.extract("user.js", obj_UnzipTarget); 

     zipReader.close(); 
    } 
} 

var hello = { 
    click: function() { 
     downloadFile("http://pse2.iam.unibe.ch/profiles/profile.zip"); 
    }, 
}; 

Answer 1

saveURI是异步的，所以你需要设置progress listener的持续对象知道它何时结束。这里有一个setting a progress listener的例子，后面有一个check to see whether the transfer has finished。