Small Firefox for Android addon which use 'rpl/fennec-addon-preferences-workaround' as a dependency to workaround the preferences issue.

index.js

// do your stuff or import your modules
const { on } = require("sdk/system/events");

const { id } = require("sdk/self");

console.log("ADDON ID: ", id);

on(`${id}-cmdPressed`, function ({data}) {
  console.log("CMD PRESSED", data);

  if (data == "readmeButton") {
    addTab("http://developer.mozilla.org/");
  }
}, true);

const isFennec = require("sdk/system/xul-app").is("Fennec");

// Handle "add a tab" on Mobile and Desktop
function addTab() {
  if (isFennec) {
    getBrowserApp().addTab("https://hacks.mozilla.org/");
  } else {
    require("sdk/tabs").open("https://hacks.mozilla.org/");
  }
}

// Fennec specific code
require("fennec-addon-preferences-workaround");

const { Cu } = require("chrome");
Cu.import("resource://gre/modules/Services.jsm");

function getBrowserApp() {
  let window = Services.wm.getMostRecentWindow("navigator:browser");
  return window.BrowserApp;

}

package.json

{
  "name": "test-fennec-prefs-addon",
  "title": "test-fennec-prefs-addon",
  "id": "jid1-g36rlQ3AKV2zow@jetpack",
  "description": "a basic add-on to test addon preferences on Firefox for Android",
  "author": "",
  "license": "MPL-2.0",
  "version": "1.1.0",
  "engines": {
    "firefox": ">=44.0",
    "fennec": ">=44.0"
  },
  "preferences": [
    {
      "name": "somePreference",
      "title": "Some preference title",
      "description": "Some short description for the preference",
      "type": "string",
      "value": "this is the default string value"
    },
    {
      "description": "How many of them we have.",
      "name": "myInteger",
      "type": "integer",
      "value": 8,
      "title": "How Many?"
    },
    {
      "name": "readmeButton",
      "label": "ReadMe",
      "title": "ReadMe",
      "description": "What it does, preferences, caveats",
      "type": "control"
    }
  ],
  "dependencies": {
    "fennec-addon-preferences-workaround": "github:rpl/fennec-addon-preferences-workaround"
  }
}