Although I haven't personally tested this approach, one potential solution could be redirecting from the service worker's fetch
event handler to an HTML page that utilizes a specific technique to close itself immediately.
The implementation could look something like this:
self.addEventListener('fetch', (event) => {
// ...process the incoming event.request body here...
// Once you're done, respond with a redirect:
event.respondWith(Response.redirect('/self-closing-page.html', 303));
});
Then, the /self-closing-page.html
web page would be responsible for closing itself, potentially returning you to the original Android app environment.