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    Code snippets

    This article includes code snippets to help you write an add-on for Firefox for Android. For additional code samples, check out the Firefox for Android Add-ons Github repo.

    Obtain NativeWindow and BrowserApp object with add-on SDK

    The NativeWindow and BrowserApp object are only available to privileged code running on Firefox for Android, and is intended for use by Firefox for Android add-ons.
    // Obtain component object : Chrome Authority
    var { Cu } = require("chrome");
    // Obtain commonly used services : Services.jsm
    function getNativeWindow() {
    	let window = Services.wm.getMostRecentWindow("navigator:browser");
    	return window.NativeWindow;
    function getBrowserApp() {
    	let window = Services.wm.getMostRecentWindow("navigator:browser");
    	return window.BrowserApp;

    Tabs and Browsers

    Most tab and browser management happens through the BrowserApp object. Because Firefox on Android uses both a native UI and a JavaScript Gecko layer, tabs need to be synchronized. Every tab has an ID which is used to identify it when interacting with the native UI.

    Waiting for UIReady

    Before trying to access any methods or properties of the BrowserApp object, you must wait for the code to be properly initialized. That typically happens in the "load" handler for the chrome browser window. This can lead to races if an add-on also uses the "load" event to do it's initialization. An easy way around this is to use the BrowserApp "UIReady" event.

    let addPageLoadListener = function() {
      BrowserApp.deck.addEventListener("load", onPageLoad, false);
    if(BrowserApp.deck) {
      // BrowserApp.deck has been initialized.
    } else {
      // Use the global chrome window to wait for BrowserApp to initialize.
      window.addEventListener("UIReady", function onUIReady(){
        window.removeEventListener("UIReady", onUIReady, false);
      }, false);

    Selected Tab and Browser

    // gets the array of open tabs
    // gets the selected tab
    // gets the selected browser
    // gets the selected browser (a shortcut)

    Looking up Tabs and Browsers

    Sometimes you have a reference to an object and want to lookup the Tab or Browser associated with that object.

    // Lookup tab using an ID
    let tab = BrowserApp.getTabForId(aID);
    // Lookup tab using a browser
    let tab = BrowserApp.getTabForBrowser(aBrowser);
    // Lookup tab using a DOM window
    let tab = BrowserApp.getTabForWindow(aWindow);
    // Lookup browser using a tab
    let browser = tab.browser;
    // Lookup browser using a DOM window
    let browser = BrowserApp.getBrowserForWindow(aWindow);
    // Lookup browser using a DOM document
    let browser = BrowserApp.getBrowserForDocument(aDocument);

    Tab Management

    // Adding a tab
    let tab = BrowserApp.addTab();
    // Close a tab
    // Select a tab
    // Listening for tab events
    function watchTab(aEvent) {
      // the target is a XUL browser element
      let browser =;
    BrowserApp.deck.addEventListener("TabOpen", watchTab, false);
    BrowserApp.deck.addEventListener("TabClose", watchTab, false);
    BrowserApp.deck.addEventListener("TabSelect", watchTab, false);

    Detecting Page Loads

    function onPageLoad(aEvent) {
      // the target is an HTMLDocument
      let doc = aEvent.originalTarget;
      let browser = BrowserApp.getBrowserForDocument(doc);
      let tab = BrowserApp.getTabForBrowser(browser);
    BrowserApp.deck.addEventListener("load", onPageLoad, true);

    Detecting Private Browsing Mode

    Private browsing mode in Firefox for Android is per-tab, not per-window

    function isPrivateTab(aTab) {
      return aTab.browser.docShell.QueryInterface(Components.interfaces.nsILoadContext).usePrivateBrowsing;
    BrowserApp.addTab("", {isPrivate: isPrivateTab(BrowserApp.selectedTab)});

    Supporting both desktop and mobile

    The same add-on can support both desktop and mobile versions of Firefox. Some of the capabilities between the platforms are different, and may require some pieces of separate logic.

    Detecting XUL support

    Mobile add-ons do not support using XUL for the UI. Mobile UI can be implemented in HTML. To detect if the platform supports XUL:

    function isXULAvailable() {
      return Components.classes[";1"].getService(Components.interfaces.nsIXULRuntime)
        .widgetToolkit.toLowerCase() != "android"

    Document Tags and Contributors

    Contributors to this page: MarkFinkle, Np, Tobias Schmidbauer, leibovic, wbamberg, backy0175
    Last updated by: leibovic,
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