如何通过离线模式打开的网页访问二维码

{
  "name": "My Web App",
  "icons": [
    {
      "src": "icon.png",
      "sizes": "192x192",
      "type": "image/png"
    }
  ],
  "theme_color": "#ffffff",
  "background_color": "#ffffff",
  "display": "standalone"
}

<link rel="manifest" href="manifest.json">

self.addEventListener('install', function(event) {
  event.waitUntil(
    caches.open('my-cache').then(function(cache) {
      return cache.addAll([
        '/',
        '/index.html',
        '/styles.css',
        '/script.js'
      ]);
    })
  );
});

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

<script>
  if ('serviceWorker' in navigator) {
    navigator.serviceWorker.register('service-worker.js');
  }
</script>