未触发Angular Service Worker可用事件

Question

我正在尝试按以下说明配置服务工作者：https://angular.io/guide/service-worker-getting-started，但是它不起作用。

数据

1. 首先，我创建一个新服务：

    export class CheckForUpdateService {

      constructor(updates: SwUpdate, @Inject(PLATFORM_ID) private platformId: Object) {
        if(isPlatformBrowser(this.platformId) && updates.isEnabled) {
          console.log('create update service');
          updates.available.subscribe(event => {
            console.log('current version is', event.current);
            console.log('available version is', event.available);
          });
          updates.activated.subscribe(event => {
            console.log('old version was', event.previous);
            console.log('new version is', event.current);
          });
          interval(5000).subscribe(() => {
            updates.checkForUpdate().then(() => console.log('checking for updates'));
          });
          updates.available.subscribe(event => {
            alert('new version available');
            updates.activateUpdate().then(() => {
              alert('prepare for reload');
              document.location.reload();
            });
          });
        }
      }
    }

1. 我将此模块导入AppComponent以将其包含在捆绑软件中。

    export class AppComponent {
          constructor(checkForUpdate: CheckForUpdateService) {
          }
        }

1. 我使用ng build --prod和http-server软件包运行服务器
2. 在Chrome DevTools网络标签中，I see these requests在控制台I see this

ngsw.json的内容：

    {
          "configVersion": 1,
          "index": "/index.html",
          "assetGroups": [
            {
              "name": "app",
              "installMode": "prefetch",
              "updateMode": "prefetch",
              "urls": [
                "/5.d50f075c73ef3cb4c819.js",
                "/6.6d79c1c2e71a562b0e26.js",
                "/7.f71cb33295df19ab0c82.js",
                "/common.c67594673251692e7d02.js",
                "/favicon.ico",
                "/index.html",
                "/main.3c8177476921b6cb50a2.js",
                "/polyfills.9a9cb9ce969a4ed9e53e.js",
                "/runtime.9288bbbd9a0917a9291a.js",
                "/scripts.9e2559654737670d2e9e.js",
                "/styles.76eb17c699edd3b8c83d.css"
              ],
              "patterns": []
            },
            {
              "name": "assets",
              "installMode": "lazy",
              "updateMode": "prefetch",
              "urls": [
                "/assets/icons/icon-128x128.png",
                "/assets/icons/icon-144x144.png",
                "/assets/icons/icon-152x152.png",
                "/assets/icons/icon-192x192.png",
                "/assets/icons/icon-384x384.png",
                "/assets/icons/icon-512x512.png",
                "/assets/icons/icon-72x72.png",
                "/assets/icons/icon-96x96.png",
                "/assets/shared/fonts/Lato-Black.woff",
                "/assets/shared/fonts/Lato-Black.woff2",
                "/assets/shared/fonts/Lato-Bold.woff",
                "/assets/shared/fonts/Lato-Bold.woff2",
                "/assets/shared/fonts/Lato-Regular.woff",
                "/assets/shared/fonts/Lato-Regular.woff2",
                "/assets/shared/fonts/Lato-Semibold.woff",
                "/assets/shared/fonts/Lato-Semibold.woff2",
                "/assets/sprites/shared.svg"
              ],
              "patterns": []
            }
          ],
          "dataGroups": [],
          "hashTable": {
            "/5.d50f075c73ef3cb4c819.js": "3083c7fa0b549bb934af4b413c67f0b93d7d1f0b",
            "/6.6d79c1c2e71a562b0e26.js": "bb2cdcd9493f3346fe834f396e82c154e9339eaa",
            "/7.f71cb33295df19ab0c82.js": "6a9aed93736f8472f4477ab6a9b8141bd0ef90a0",
            "/assets/icons/icon-128x128.png": "dae3b6ed49bdaf4327b92531d4b5b4a5d30c7532",
            "/assets/icons/icon-144x144.png": "b0bd89982e08f9bd2b642928f5391915b74799a7",
            "/assets/icons/icon-152x152.png": "7479a9477815dfd9668d60f8b3b2fba709b91310",
            "/assets/icons/icon-192x192.png": "1abd80d431a237a853ce38147d8c63752f10933b",
            "/assets/icons/icon-384x384.png": "329749cd6393768d3131ed6304c136b1ca05f2fd",
            "/assets/icons/icon-512x512.png": "559d9c4318b45a1f2b10596bbb4c960fe521dbcc",
            "/assets/icons/icon-72x72.png": "c457e56089a36952cd67156f9996bc4ce54a5ed9",
            "/assets/icons/icon-96x96.png": "3914125a4b445bf111c5627875fc190f560daa41",
            "/assets/shared/fonts/Lato-Black.woff": "a612d1d7601bf159b10aacd615a0a5077dfdd2ca",
            "/assets/shared/fonts/Lato-Black.woff2": "15cbaaac8386285a78fce886eb34a85aa0945496",
            "/assets/shared/fonts/Lato-Bold.woff": "fee666528a8a52ad95015218f5f606e4819b0f26",
            "/assets/shared/fonts/Lato-Bold.woff2": "d50d1a56d66cf1991f7c21c0ca7b7501c504868d",
            "/assets/shared/fonts/Lato-Regular.woff": "750dda1f007c465fded21890968b5417000f0f3d",
            "/assets/shared/fonts/Lato-Regular.woff2": "2243bf872bf09530c171f1ea0bba979f87c5260f",
            "/assets/shared/fonts/Lato-Semibold.woff": "a4a0fbb0d03f2175ad34fc0ed467761e4a8c12f4",
            "/assets/shared/fonts/Lato-Semibold.woff2": "c9a987a1a51656fd069593d05a81f8dffb203d54",
            "/assets/sprites/shared.svg": "f49e3ecf0e0a0abb6637e8024d00386db9f88529",
            "/common.c67594673251692e7d02.js": "ee2d2410c3954e545f393d37de7f2958a6c5b589",
            "/favicon.ico": "84161b857f5c547e3699ddfbffc6d8d737542e01",
            "/index.html": "082db5a4f46abab95756c176fa71cf7fa3f9a2bc",
            "/main.3c8177476921b6cb50a2.js": "015f68f73d8ccd90f50c5d626b4ef356afb65187",
            "/polyfills.9a9cb9ce969a4ed9e53e.js": "8b97e0b0f844afd0f56ce19901a24b6892737aea",
            "/runtime.9288bbbd9a0917a9291a.js": "7a4808385055b952e1c8152b2da283223d887492",
            "/scripts.9e2559654737670d2e9e.js": "de3743672bea0396cc95f4e1ceb4fe0a41e50149",
            "/styles.76eb17c699edd3b8c83d.css": "b1b9fb99c63561410b127423c33072bc2f7ce191"
          },
          "navigationUrls": [
            {
              "positive": true,
              "regex": "^\\/.*$"
            },
            {
              "positive": false,
              "regex": "^\\/(?:.+\\/)?[^/]*\\.[^/]*$"
            },
            {
              "positive": false,
              "regex": "^\\/(?:.+\\/)?[^/]*__[^/]*$"
            },
            {
              "positive": false,
              "regex": "^\\/(?:.+\\/)?[^/]*__[^/]*\\/.*$"
            }
          ]
        }

看看：

"/5.d50f075c73ef3cb4c819.js": "3083c7fa0b549bb934af4b413c67f0b93d7d1f0b"

当我更改模块中的某些代码并使用ng build --prod重建项目时，ngsw.json中模块的哈希值发生了变化：

"/5.c68a247a88c3a07be21b.js": "b279b664a0848071c59da5c33e31de0f3eb952a9"

但未触发可用事件。

为什么？