samples/web/vision_challenge/flutter_service_worker.js

'use strict';
const MANIFEST = 'flutter-app-manifest';
const TEMP = 'flutter-temp-cache';
const CACHE_NAME = 'flutter-app-cache';
const RESOURCES = {
  "index.html": "51839f812a32cce7ac40ca488295da30",
"/": "51839f812a32cce7ac40ca488295da30",
"main.dart.js": "4d6ec2b4fd2009ca0d084751f77d6fcd",
"assets/LICENSE": "214b42b1da140cbb9f54bc2f61ee17e4",
"assets/AssetManifest.json": "752c8e3f4304d36d239f2c923af773c1",
"assets/FontManifest.json": "580ff1a5d08679ded8fcf5c6848cece7",
"assets/fonts/MaterialIcons-Regular.ttf": "56d3ffdef7a25659eab6a68a3fbfaf16",
"assets/assets/preview.png": "b743324f80ce372be751c15d192bf08b",
"assets/assets/99.png": "12e834717963f504585a97def43969f5",
"assets/assets/10.png": "0e0f15801901200dd4b015fd8f26414b",
"assets/assets/35.png": "adcba14022a4d6cc03accde3c2853de1",
"assets/assets/20.png": "78f70ca0374373a20937c46e6bb1f241",
"assets/assets/p0.jpg": "927abb9bdc90417cc0804214ba5c1198",
"assets/assets/p1.jpg": "dae69d14475c8d97bdd5dac810f28f4a",
"assets/assets/30.png": "ac627311b29bb33af59f86b5af96303e",
"assets/assets/40.png": "011f2a540275808f0a829ffcb7461a77",
"assets/assets/45.png": "a5242198fb3a27da0ee3a6f9ca72ce8f"
};

// The application shell files that are downloaded before a service worker can
// start.
const CORE = [
  "main.dart.js",
"/",
"index.html",
"assets/LICENSE",
"assets/AssetManifest.json",
"assets/FontManifest.json"];

// During install, the TEMP cache is populated with the application shell files.
self.addEventListener("install", (event) => {
  return event.waitUntil(
    caches.open(TEMP).then((cache) => {
      return cache.addAll(CORE);
    })
  );
});

// During activate, the cache is populated with the temp files downloaded in
// install. If this service worker is upgrading from one with a saved
// MANIFEST, then use this to retain unchanged resource files.
self.addEventListener("activate", function(event) {
  return event.waitUntil(async function() {
    try {
      var contentCache = await caches.open(CACHE_NAME);
      var tempCache = await caches.open(TEMP);
      var manifestCache = await caches.open(MANIFEST);
      var manifest = await manifestCache.match('manifest');

      // When there is no prior manifest, clear the entire cache.
      if (!manifest) {
        await caches.delete(CACHE_NAME);
        for (var request of await tempCache.keys()) {
          var response = await tempCache.match(request);
          await contentCache.put(request, response);
        }
        await caches.delete(TEMP);
        // Save the manifest to make future upgrades efficient.
        await manifestCache.put('manifest', new Response(JSON.stringify(RESOURCES)));
        return;
      }

      var oldManifest = await manifest.json();
      var origin = self.location.origin;
      for (var request of await contentCache.keys()) {
        var key = request.url.substring(origin.length + 1);
        if (key == "") {
          key = "/";
        }
        // If a resource from the old manifest is not in the new cache, or if
        // the MD5 sum has changed, delete it. Otherwise the resource is left
        // in the cache and can be reused by the new service worker.
        if (!RESOURCES[key] || RESOURCES[key] != oldManifest[key]) {
          await contentCache.delete(request);
        }
      }
      // Populate the cache with the app shell TEMP files, potentially overwriting
      // cache files preserved above.
      for (var request of await tempCache.keys()) {
        var response = await tempCache.match(request);
        await contentCache.put(request, response);
      }
      await caches.delete(TEMP);
      // Save the manifest to make future upgrades efficient.
      await manifestCache.put('manifest', new Response(JSON.stringify(RESOURCES)));
      return;
    } catch (err) {
      // On an unhandled exception the state of the cache cannot be guaranteed.
      console.error('Failed to upgrade service worker: ' + err);
      await caches.delete(CACHE_NAME);
      await caches.delete(TEMP);
      await caches.delete(MANIFEST);
    }
  }());
});

// The fetch handler redirects requests for RESOURCE files to the service
// worker cache.
self.addEventListener("fetch", (event) => {
  var origin = self.location.origin;
  var key = event.request.url.substring(origin.length + 1);
  // If the URL is not the the RESOURCE list, skip the cache.
  if (!RESOURCES[key]) {
    return event.respondWith(fetch(event.request));
  }
  event.respondWith(caches.open(CACHE_NAME)
    .then((cache) =>  {
      return cache.match(event.request).then((response) => {
        // Either respond with the cached resource, or perform a fetch and
        // lazily populate the cache.
        return response || fetch(event.request).then((response) => {
          cache.put(event.request, response.clone());
          return response;
        });
      })
    })
  );
});