Develop apps and explore the world (wide web)

BJJ Tracker

World Wide Web

The web, as a platform, is open and free. Unlike native app markets, we don’t have to wait for software to be approved by any third-party. It works across any device or operating system that has a web browser. (Which is why standards across browsers is so important). But, until recently web-apps faced limitations. Not having full access to a device’s hardware and operating system was an issue – but that’s being fixed as more native APIs are being added to modern web browsers.

A disadvantage of having a web-only app was losing out on the discoverability that comes with having it listed in a searchable marketplace. Adding a web-app to your device home screen, from a web browser, is not intuitive to average users. Fortunately, the Google Play Market allows us to upload an app file that links to a progressive web app.

This involves a new protocol,  Trusted Web Activities, as “a way to integrate your web-app content such as your PWA with your Android app“. The PWA leverages Digital Asset Links to “declare that it is associated with a specific Android app.

Progressive web apps

I decided to try this out with one of my web-apps, BJJ Tracker. You can read about how I first built it on another blog post.

I had to make sure it qualified as a PWA. It needed offline support, as well as any other features that would make it feel like a native app. Google Chrome’s developer tools has a section called “Audits” that helped me identify such opportunities.

progressive web app audit

The first step was to create a “service worker” JavaScript file, and register it when BJJ Tracker loads.

if('serviceWorker' in navigator) {
           .then(function() { console.log("Service Worker Registered"); })
           .catch(error => {

I added the above code to a shared file that loads on every page of my app.  Below is an example service worker file. This file downloads any vital assets to a user’s device, and later loads them from the cache. Including a polyfill ensures that the cache methods exist (in case the browser does not support them natively). “We need to use the polyfill because the Cache API is not yet fully supported in all browsers.


self.addEventListener('install', function(e) {
 e.waitUntil('bjjtracker').then(function(cache) {
    return cache.addAll([
    }).catch(error => {

self.addEventListener('fetch', function(event) {
		caches.match(event.request).then(function(response) {
			return response || fetch(event.request);
		}).catch(error => {

Read the documentation on Google’s developer portal.

Next, I created a “manifest” file. This file is written in JSON format. It helps describe how the web-app behaves once “installed”. It handles things such as app icon images and meta data.

  "name": "BJJ Tracker",
  "lang": "en-US",
  "short_name": "BJJ Tracker",
  "start_url": "/",
  "display": "standalone",
  "background_color": "#2a4d69",
  "theme_color": "#2a4d69",
  "description": "Track Brazilian Jiu Jitsu progress and fitness goals.",
  "icons": [{
    "src": "img/homescreen48.png",
    "sizes": "48x48",
    "type": "image/png"
  }, {
    "src": "img/homescreen72.png",
    "sizes": "72x72",
    "type": "image/png"
  }, {
    "src": "img/homescreen96.png",
    "sizes": "96x96",
    "type": "image/png"
  }, {
    "src": "img/homescreen144.png",
    "sizes": "144x144",
    "type": "image/png"
  }, {
    "src": "img/homescreen168.png",
    "sizes": "168x168",
    "type": "image/png"
  }, {
    "src": "img/homescreen192.png",
    "sizes": "192x192",
    "type": "image/png"
  }, {
    "src": "img/homescreen512.png",
    "sizes": "512x512",
    "type": "image/png"

I created the image assets using open source software.

Image assets created with GIMP
Image assets created with GIMP

The manifest needs to be referenced by the app. I added a link tag to a shared <head> file. Additionally, I included a few other meta tags that let browsers know to treat this website as an app.

<link rel="manifest" href="/manifest.json">
<meta name="theme-color" content="#005b96"/>
<meta name="mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="msapplication-starturl" content="/">

Android Studio

A signed app bundle is generated from Android Studio.  I use a sample project from Google Chrome Labs as a template. We can clone that repository, and update the “/svgomg-twa/app/build.gradle” settings to point to our PWA.

app gradle settings
TWA to wrap SVGOMG in an Android App

The app’s icon files can be generated using an online tool. The downloadable bundle can be dropped into “/svgomg-twa/app/src/main/res/“.

icon generator

When creating the app bundle (“Build > Generate Signed Bundle/APK”) we’ll need a signing key. I created a new one, and named the file mykeystore.keystore.

An “assetlinks.json” file needs to be uploaded to the web app’s host to satisfy the Digital Asset Links requirement.  “The Digital Asset Links protocol and API enable an app or website to make public, verifiable statements about other apps or websites.” This confirms ownership of the PWA so that it can be linked to our app in the Play Store. To generate this file, first we’ll need to get the fingerprint from the signing key we used:

keytool -list -v -keystore mykeystore.keystore -alias mykeystore -storepass password-here  -keypass password-here

That command shows us the certificate fingerprints. Copy the SHA256 value. It is used with Google’s Statement List Generator to create the contents of the assetlinks.json file. The statement file is then placed in a “.well-known” directory on the root of our PWA domain (eg.

Finally, I visited the Google Play Console. Besides uploading the .apk file, I also needed to include screenshots, featured image files, and complete a content rating survey – amongst other things. Since my app has been approved, you can now find it in the Google Play Market.

BJJ Tracker in the Google Play Store.

This app is a side project I use to toy with new web technologies. I’m trying to drive traffic to it so that I can experiment with optimizing conversions. I’m using it as a trial grounds for another software service called SplitWit. SplitWit is focused on optimizing conversions for the web, and helping digital marketers reach their goals. You can read about it on another post from this blog.

bjj tracker app

Open Source Society

Sometime during the 1950’s television sets had begun to become widely available and fairly affordable. Noting this point as the advent of entertainment focused telecommunications; art had begun to be understood as a trivial distraction to conservative intellectuals. The vegetating trance of the television, typically allowing the mind to enter a state of ‘cruise control,’ could be attributed to the public’s low level of input towards programming. Although the Internet seems to descend from this legacy of infotainment, something quite different is going on. While television preaches endless forms of false happiness through consumerism, the design of the contemporary web aims to facilitate “creativity, information sharing, and, most notably, collaboration among users (Wikipedia – Web 2.0)” This arrangement comprises the core methodology of the Open Source Revolution that is beginning to reshape our traditions and lead us towards a new renaissance of gnosis.

Philosopher Terence McKenna, reminding us that “culture is not your friend (1999),” advises to resist the epistemological disease of autocratic content by creating our own art. Through venues such as Youtube and MySpace, music, art, film, and photography, even mildly entertaining, is now able to draw large audiences and develop into a well received meme. Further, the Wiki archetype has effectively turned the amateur into the expert. McKenna often refers to a revival of the archaic, which is set to take place as a reaction to the patriarchal model of the elite handing knowledge down, and forsaking personal revelation. The proliferation of open source programs, granting users the ability to freely edit and redistribute computer software, manifests the artistic position towards which society must move. The world is shrinking in to a global village thru mass media, and the common majority must take direct control in order to reconnect and reconcile into cosmic consciousness.

The term ‘global village’ is often used metaphorically to describe the internet and World Wide Web. Philosopher Marshall McLuhan predicted that a global village would be tribal in character. The open source operating system Ubuntu, a distribution of Linux (a prime example of free software and open source development), derives its name from the South African philosophical notion of humanitarianism. Interestingly, this juxtaposition of concept and utility represents the new archetype of culture towards which the Open Source Revolution is driving. Projects such as Wikipedia, an open content encyclopedia, are able to maintain their integrity, accuracy, and scope through an effort of community and collaboration. The Open Source Revolution lends new drive to innovation, epistemology, peer support, and ultimately an altruism that trumps the capitalist agenda of elitism. I feel that we must adopt the concept of Open Source as a new organizational model for society.

Should the open source paradigm stay confined to computer software and the internet, or should we move to adopt it as a new model for social organization?

“In a global village where we have instant access to innumerable beliefs around the world, we have come to realize the relativity of what we think”

-Walter Anderson