PWA - beforeinstallprompt not called - progressive-web-apps

Question

Hello I'm trying to install a custom PWA "Add to Homescreen".
The ServiceWorkerRegistration is successful.
But the function beforeinstallpromp is not calling after register.
<script type="text/javascript">
function request_debug(paramdata){
document.getElementById('output').innerHTML += '<BR>'+ paramdata;
}
window.addEventListener('load', function() {
document.getElementById('output').style.display = "block";
if('serviceWorker' in navigator) {
navigator.serviceWorker.register('sw.js').then(function(registration) {
console.log('Service worker registrado com sucesso:', registration);
request_debug(registration);
}).catch(function(error) {
console.log('Falha ao Registrar o Service Worker:', error);
request_debug(error);
});
var isTooSoon = true;
window.addEventListener('beforeinstallprompt', function(e) {
//e.preventDefault();
//e.prompt();
//promptEvent = e;
request_debug(' window.addEventListener beforeinstallprompt fired!')
if (isTooSoon) {
//e.preventDefault(); // Prevents prompt display
// Prompt later instead:
setTimeout(function() {
isTooSoon = false;
e.prompt(); // Throws if called more than once or default not prevented
}, 4000);
}
});
}else{
console.log('serviceWorker not in navigator');
request_debug('serviceWorker not in navigator');
}
});
</script>
Also my service worker in root directory...
HTTPS is secure!
my manifest:
{
"background_color": "purple",
"description": "lojaportaldotricot TESTE",
"display": "standalone",
"icons": [
{
"src": "/componentes/serviceWorker/fox-icon.png",
"sizes": "192x192",
"type": "image/png"
}
],
"name": "lojaportaldotricot",
"short_name": "lojaportaldotricot",
"start_url": "/dashboard"
}
It's only workes when I set "Enable" chrome://flags/#bypass-app-banner-engagement-checks
Edit: Look's like I've found the problem. The Audits tabs of Chrome's DevTools(F12) gives debugging information.

Answer 1

Try this :
<script>
let deferredPrompt;
window.addEventListener('beforeinstallprompt', function(event) {
// Prevent Chrome 67 and earlier from automatically showing the prompt
e.preventDefault();
// Stash the event so it can be triggered later.
deferredPrompt = e;
});
// Installation must be done by a user gesture! Here, the button click
btnAdd.addEventListener('click', (e) => {
// hide our user interface that shows our A2HS button
btnAdd.style.display = 'none';
// Show the prompt
deferredPrompt.prompt();
// Wait for the user to respond to the prompt
deferredPrompt.userChoice
.then((choiceResult) => {
if (choiceResult.outcome === 'accepted') {
console.log('User accepted the A2HS prompt');
} else {
console.log('User dismissed the A2HS prompt');
}
deferredPrompt = null;
});
});
</script>
beforeinstallprompt will only be fired when some conditions are true :
The PWA must not already be installed
Meets a user engagement heuristic (previously, the user had to interact with the domain for at least 30 seconds, this is not a requirement anymore).
Your web app must include a web app manifest.
Your web app must be served over a secure HTTPS connection.
Has registered a service worker with a fetch event handler.

Answer 2

Along with all of those steps above, also check that the app is uninstalled here:
chrome://apps
Just deleting the app from the Chrome Apps folder on your Mac does not seem to remove it from Chrome
If the app was previously installed, the beforeinstallprompt will not be triggered, and no errors will be thrown either :(

Answer 3

Yes, the "start_url" is incorrect in the manifest.
IF ANY PART OF THE MANIFEST IS BROKEN 'beforeinstallprompt' is not fired.
The event is not fired because... the manifest start_url is incorrect.
My favorite way to figure this out is to look in the > NETWORK tab of DevTools for 404's.
AND the other way to see why manifest is broken is to run > AUDIT in DevTools and see what the error is. Like what #sealabr found:
"Failures: Service worker does not successfully serve the manifest's start_url, Timed out waiting for fetched start_url.' Which means the 'start_url"
This thread was a big help troubleshooting production. Thanks.

Answer 4

Are you including the manifest file in the page header?
<link rel="manifest" href="/manifest.json">

Answer 5

To whoever needs to read this: A little side-note that I ran into when working on my Vue3 app while trying to figure out the prompt:
The beforeInstallPrompt will trigger shortly after the page load.
So make sure you set up the event listener close to the page load. Took me a couple of hours to find this out. I was trying to add the event listener somewhere down the line of onboarding the user. Way after the page load. And couldn't figure out why the prompt didn't show.

Answer 6

here is another reason why beforeinstallprompt is not triggered on a mobile device (observed on an Android device with Chrome):
A symbol file defined in manifest.webmanifest could not be found on the web server (the mobile browser reported a 404). That was the reason why beforeinstallprompt was not triggered in my case.
#example
// your manifest
{
/* ... */
"icons": [
{
"src": "maskable_icon_x192.png",
"sizes": "192x192",
"type": "image/png",
"purpose": "any maskable"
},
/*...*/
]
}
Make sure that all icon files (such as maskable_icon_x192.png) are present on your web server.
All the best,
Tom