服务工作者不返回自定义离线页面，而是返回默认的“离线”页面

Question

我有一个服务人员，如果您处于离线状态，我想返回一个离线页面。我意识到你必须先缓存离线页面，所以我这样做了。当我将其缓存并使用 chrome 开发工具将网络限制为脱机时，它显示了默认的脱机页面！我不知道如何在离线时调出页面。如果这会改变任何事情，我正在使用 chromebook。这是我的代码（顺便说一下，我对服务人员完全陌生）：

this.addEventListener('install', function(event) {
 event.waitUntil(
 caches.open('v1').then(function(cache) {
   return cache.addAll(['../offline.html','../images/ico/ico.jpg']); 
 })
 );
});
this.addEventListener('fetch', function(event) {
    event.respondWith(
       caches.match(event.request)
           .then(function(response) {
               // If fetch fails, we return offline.html from cache.
               return fetch(event.request)
                   .catch(err => {
                       return caches.match('../offline.html');
                   });
           }
       )
   );
});

Answer 1

用这个替换您的 fetch 事件代码。对于每个请求，都会调用您的 fetch 事件，它会检查您的请求是否在缓存文件列表中找到，然后它将从那里提供文件，否则它将进行 fetch 调用以从服务器获取文件。

self.addEventListener('fetch', (event) => {
  // We only want to call event.respondWith() if this is a navigation request
  // for an HTML page.
  if (event.request.mode === 'navigate') {
    event.respondWith((async () => {
      try {
        // First, try to use the navigation preload response if it's supported.
        const preloadResponse = await event.preloadResponse;
        if (preloadResponse) {
          return preloadResponse;
        }

        const networkResponse = await fetch(event.request);
        return networkResponse;
      } catch (error) {
        // catch is only triggered if an exception is thrown, which is likely
        // due to a network error.
        // If fetch() returns a valid HTTP response with a response code in
        // the 4xx or 5xx range, the catch() will NOT be called.
        console.log('Fetch failed; returning offline page instead.', error);

        const cache = await caches.open(CACHE_NAME);
        const cachedResponse = await cache.match(OFFLINE_URL);
        return cachedResponse;
      }
    })());
  }

  // If our if() condition is false, then this fetch handler won't intercept the
  // request. If there are any other fetch handlers registered, they will get a
  // chance to call event.respondWith(). If no fetch handlers call
  // event.respondWith(), the request will be handled by the browser as if there
  // were no service worker involvement.
});