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How to start regular download from addon

Add-on development for Firefox. I find that I need to be able to start the download as if the user requested it, that is, either showed the normal file save dialog box, or saved the file to where the user prefers, because it can be configured according to> content settings.

In each individual message or documentation regarding the download, you should consider only the scenario where I know where to download the file, but in this case this is not what I need, in this case it should be as if the user started to download .

How can this be done preferably using SDK methods?

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2 answers

Well, you could just initiate the actual save.

Initiation of a save link from your code:
Oncommand is equal in the context menu gContextMenu.saveLink();. saveLink () is determined: chrome://browser/content/nsContextMenu.js. It does some cleaning and then calls saveHelper (), which is defined in one file . You can simply call saveHelper () with the appropriate arguments. It is included in the panel chrome://browser/content/web-panels.xulwith:

<script type="application/javascript" 
            src="chrome://browser/content/nsContextMenu.js"/>

Then a variable gContextMenuis declared that is declared chrome://browser/content/browser.jsas null: in the onpopupshowing event handler for context menus. It returns: 'gContextMenu = null;' in the event handler .
gContextMenu = new nsContextMenu(this, event.shiftKey);


onpopuphiding

, :

let urlToSave = "http://stackoverflow.com/questions/26694442";
let linkText = "Some Link text";

//  Add a "/" to un-comment the code appropriate for your add-on type.
/* Overlay and bootstrap:
const Cc = Components.classes;
const Ci = Components.interfaces;
const Cr = Components.results;
//*/
/* Add-on SDK:
var {Cc, Ci, Cr} = require("chrome");
//*/

if (window === null || typeof window !== "object") {
    //If you do not already have a window reference, you need to obtain one:
    //  Add a "/" to un-comment the code appropriate for your add-on type.
    /* Add-on SDK:
    var window = require('sdk/window/utils').getMostRecentBrowserWindow();
    //*/
    /* Overlay and bootstrap (from almost any context/scope):
    var window=Components.classes["@mozilla.org/appshell/window-mediator;1"]
                         .getService(Components.interfaces.nsIWindowMediator)
                         .getMostRecentWindow("navigator:browser");        
    //*/
}

//Create an object in which we attach nsContextMenu.js.
//  It needs some support properties/functions which
//  nsContextMenu.js assumes are part of its context.
let contextMenuObj = {
    makeURI: function (aURL, aOriginCharset, aBaseURI) {
      var ioService = Cc["@mozilla.org/network/io-service;1"]
                                .getService(Ci.nsIIOService);
      return ioService.newURI(aURL, aOriginCharset, aBaseURI);
    },
    gPrefService: Cc["@mozilla.org/preferences-service;1"]
                            .getService(Ci.nsIPrefService)
                            .QueryInterface(Ci.nsIPrefBranch),
    Cc: Cc,
    Ci: Ci,
    Cr: Cr
};

Cc["@mozilla.org/moz/jssubscript-loader;1"]
        .getService(Ci.mozIJSSubScriptLoader)
        .loadSubScript("chrome://browser/content/nsContextMenu.js"
                       ,contextMenuObj);

//Re-define the initMenu function, as there is not a desire to actually
//  initialize a menu.        
contextMenuObj.nsContextMenu.prototype.initMenu = function() { };

let myContextMenu = new contextMenuObj.nsContextMenu();
//Save the specified URL
myContextMenu.saveHelper(urlToSave,linkText,null,true,window.content.document);

loadSubScript nsContextMenu.js:
loadSubScript saveHelper nsContextMenu.js. , Firefox. , , API. , - Firefox . saveHelper() . :

// Helper function to wait for appropriate MIME-type headers and
// then prompt the user with a file picker
saveHelper: function(linkURL, linkText, dialogTitle, bypassCache, doc) {
  // canonical def in nsURILoader.h
  const NS_ERROR_SAVE_LINK_AS_TIMEOUT = 0x805d0020;

  // an object to proxy the data through to
  // nsIExternalHelperAppService.doContent, which will wait for the
  // appropriate MIME-type headers and then prompt the user with a
  // file picker
  function saveAsListener() {}
  saveAsListener.prototype = {
    extListener: null, 

    onStartRequest: function saveLinkAs_onStartRequest(aRequest, aContext) {

      // if the timer fired, the error status will have been caused by that,
      // and we'll be restarting in onStopRequest, so no reason to notify
      // the user
      if (aRequest.status == NS_ERROR_SAVE_LINK_AS_TIMEOUT)
        return;

      timer.cancel();

      // some other error occured; notify the user...
      if (!Components.isSuccessCode(aRequest.status)) {
        try {
          const sbs = Cc["@mozilla.org/intl/stringbundle;1"].
                      getService(Ci.nsIStringBundleService);
          const bundle = sbs.createBundle(
                  "chrome://mozapps/locale/downloads/downloads.properties");

          const title = bundle.GetStringFromName("downloadErrorAlertTitle");
          const msg = bundle.GetStringFromName("downloadErrorGeneric");

          const promptSvc = Cc["@mozilla.org/embedcomp/prompt-service;1"].
                            getService(Ci.nsIPromptService);
          promptSvc.alert(doc.defaultView, title, msg);
        } catch (ex) {}
        return;
      }

      var extHelperAppSvc = 
        Cc["@mozilla.org/uriloader/external-helper-app-service;1"].
        getService(Ci.nsIExternalHelperAppService);
      var channel = aRequest.QueryInterface(Ci.nsIChannel);
      this.extListener = 
        extHelperAppSvc.doContent(channel.contentType, aRequest, 
                                  doc.defaultView, true);
      this.extListener.onStartRequest(aRequest, aContext);
    }, 

    onStopRequest: function saveLinkAs_onStopRequest(aRequest, aContext, 
                                                     aStatusCode) {
      if (aStatusCode == NS_ERROR_SAVE_LINK_AS_TIMEOUT) {
        // do it the old fashioned way, which will pick the best filename
        // it can without waiting.
        saveURL(linkURL, linkText, dialogTitle, bypassCache, false,
                doc.documentURIObject, doc);
      }
      if (this.extListener)
        this.extListener.onStopRequest(aRequest, aContext, aStatusCode);
    },

    onDataAvailable: function saveLinkAs_onDataAvailable(aRequest, aContext,
                                                         aInputStream,
                                                         aOffset, aCount) {
      this.extListener.onDataAvailable(aRequest, aContext, aInputStream,
                                       aOffset, aCount);
    }
  }

  function callbacks() {}
  callbacks.prototype = {
    getInterface: function sLA_callbacks_getInterface(aIID) {
      if (aIID.equals(Ci.nsIAuthPrompt) || aIID.equals(Ci.nsIAuthPrompt2)) {
        // If the channel demands authentication prompt, we must cancel it
        // because the save-as-timer would expire and cancel the channel
        // before we get credentials from user.  Both authentication dialog
        // and save as dialog would appear on the screen as we fall back to
        // the old fashioned way after the timeout.
        timer.cancel();
        channel.cancel(NS_ERROR_SAVE_LINK_AS_TIMEOUT);
      }
      throw Cr.NS_ERROR_NO_INTERFACE;
    } 
  }

  // if it we don't have the headers after a short time, the user 
  // won't have received any feedback from their click.  that bad.  so
  // we give up waiting for the filename. 
  function timerCallback() {}
  timerCallback.prototype = {
    notify: function sLA_timer_notify(aTimer) {
      channel.cancel(NS_ERROR_SAVE_LINK_AS_TIMEOUT);
      return;
    }
  }

  // set up a channel to do the saving
  var ioService = Cc["@mozilla.org/network/io-service;1"].
                  getService(Ci.nsIIOService);
  var channel = ioService.newChannelFromURI(makeURI(linkURL));
  if (channel instanceof Ci.nsIPrivateBrowsingChannel) {
    let docIsPrivate = PrivateBrowsingUtils.isWindowPrivate(doc.defaultView);
    channel.setPrivate(docIsPrivate);
  }
  channel.notificationCallbacks = new callbacks();

  let flags = Ci.nsIChannel.LOAD_CALL_CONTENT_SNIFFERS;

  if (bypassCache)
    flags |= Ci.nsIRequest.LOAD_BYPASS_CACHE;

  if (channel instanceof Ci.nsICachingChannel)
    flags |= Ci.nsICachingChannel.LOAD_BYPASS_LOCAL_CACHE_IF_BUSY;

  channel.loadFlags |= flags;

  if (channel instanceof Ci.nsIHttpChannel) {
    channel.referrer = doc.documentURIObject;
    if (channel instanceof Ci.nsIHttpChannelInternal)
      channel.forceAllowThirdPartyCookie = true;
  }

  // fallback to the old way if we don't see the headers quickly 
  var timeToWait = 
    gPrefService.getIntPref("browser.download.saveLinkAsFilenameTimeout");
  var timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
  timer.initWithCallback(new timerCallback(), timeToWait,
                         timer.TYPE_ONE_SHOT);

  // kick off the channel with our proxy object as the listener
  channel.asyncOpen(new saveAsListener(), null);
}
+2

@canuckistani, Downloads.jsm

let { Downloads } = require("resource://gre/modules/Downloads.jsm");
let { OS } = require("resource://gre/modules/osfile.jsm")
let { Task } = require("resource://gre/modules/Task.jsm");

Task.spawn(function () {

  yield Downloads.fetch("http://www.mozilla.org/",
                        OS.Path.join(OS.Constants.Path.tmpDir,
                                     "example-download.html"));

  console.log("example-download.html has been downloaded.");

}).then(null, Components.utils.reportError);
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