active serviceWorker不向等待的serviceWorker发送消息。

Question

，我想做什么？

我正在创建一个渐进的web应用程序，为了正确地发送升级应用程序，我正在执行一个步骤，即通知用户，一旦用户说“升级”，serviceWorker就调用skipWaiting()。

到目前为止我做了什么？

为了实现这一点，我正在跟踪一篇不错的文章https://redfin.engineering/how-to-fix-the-refresh-button-when-using-service-workers-a8e27af6df68。

为了消除复杂性，我只测试serviceWorkers之间的消息发送，以了解skipWaiting是如何工作的。我使用的是create-react-app (v"react": "^16.5.2",)，它附带了作为插件绑定的workbox。

我现在的registerServiceWorker.js看起来就像

// In production, we register a service worker to serve assets from local cache.

// This lets the app load faster on subsequent visits in production, and gives
// it offline capabilities. However, it also means that developers (and users)
// will only see deployed updates on the "N+1" visit to a page, since previously
// cached resources are updated in the background.

// To learn more about the benefits of this model, read 
// This link also includes instructions on opting out of this behavior.

const isLocalhost = Boolean(
  window.location.hostname === 'localhost' ||
    // [::1] is the IPv6 localhost address.
    window.location.hostname === '[::1]' ||
    // 127.0.0.1/8 is considered localhost for IPv4.
    window.location.hostname.match(
      /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
    )
);

export default function register() {
  if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
    // The URL constructor is available in all browsers that support SW.
    const publicUrl = new URL(process.env.PUBLIC_URL, window.location);
    if (publicUrl.origin !== window.location.origin) {
      // Our service worker won't work if PUBLIC_URL is on a different origin
      // from what our page is served on. This might happen if a CDN is used to
      // serve assets; see https://github.com/facebookincubator/create-react-app/issues/2374
      return;
    }

    window.addEventListener('load', () => {
      const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;

      if (!isLocalhost) {
        // Is not local host. Just register service worker
        registerValidSW(swUrl);
      } else {
        // This is running on localhost. Lets check if a service worker still exists or not.
        checkValidServiceWorker(swUrl);
      }
    });

    window.addEventListener('message', messageEvent => {
      const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;

      if (messageEvent.data === 'skipWaiting') {
        console.log('skipWaiting');
        return navigator.serviceWorker.getRegistration(swUrl)
          .then(registration => registration.skipWaiting());
      }

      console.log(`message=${messageEvent.data}`);
    });

    let refreshingPage;
    navigator.serviceWorker.addEventListener('controllerchange', () => {
      console.log('refreshing page now');
      if (refreshingPage) return;
      refreshingPage = true;
      window.location.reload();
    });
  }
}

function registerValidSW(swUrl) {
  navigator.serviceWorker
    .register(swUrl)
    .then(registration => {
      registration.onupdatefound = () => {
        const installingWorker = registration.installing;
        installingWorker.onstatechange = () => {
          if (installingWorker.state === 'installed') {
            if (navigator.serviceWorker.controller) {
              // At this point, the old content will have been purged and
              // the fresh content will have been added to the cache.
              // It's the perfect time to display a "New content is
              // available; please refresh." message in your web app.
              console.log('>> New content is available; please refresh.');
              navigator.serviceWorker.controller.postMessage('skipWaiting');
            } else {
              // At this point, everything has been precached.
              // It's the perfect time to display a
              // "Content is cached for offline use." message.
              console.log('Content is cached for offline use.');
            }
          }
        };
      };
    })
    .catch(error => {
      console.error('Error during service worker registration:', error);
    });
}

function checkValidServiceWorker(swUrl) {
  // Check if the service worker can be found. If it can't reload the page.
  fetch(swUrl)
    .then(response => {
      // Ensure service worker exists, and that we really are getting a JS file.
      if (
        response.status === 404 ||
        response.headers.get('content-type').indexOf('javascript') === -1
      ) {
        // No service worker found. Probably a different app. Reload the page.
        navigator.serviceWorker.ready.then(registration => {
          registration.unregister().then(() => {
            window.location.reload();
          });
        });
      } else {
        // Service worker found. Proceed as normal.
        registerValidSW(swUrl);
      }
    })
    .catch(() => {
      console.log(
        'No internet connection found. App is running in offline mode.'
      );
    });
}

export function unregister() {
  if ('serviceWorker' in navigator) {
    navigator.serviceWorker.ready.then(registration => {
      registration.unregister();
    });
  }
}

如您所见，当一个新的serviceWorker是installed时，我将发送一个postMessage作为

console.log('>> New content is available; please refresh.');
navigator.serviceWorker.controller.postMessage('skipWaiting');

我期待着用函数来处理消息。

    window.addEventListener('message', messageEvent => {
      const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;

      if (messageEvent.data === 'skipWaiting') {
        console.log('skipWaiting');
        return navigator.serviceWorker.getRegistration(swUrl)
          .then(registration => registration.skipWaiting());
      }

      console.log(`message=${messageEvent.data}`);
    });

然后，我部署我的更改，以便这个serviceWorker已经准备好了。然后，我对我的应用程序(index.html)进行了更改，现在当我部署时，我看到多条消息正在被记录，但没有一条是用skipWaiting记录的。

message=
registerServiceWorker.js:53 message=!_{"h":"I0_1548194465894"}
registerServiceWorker.js:53 message=!_{"s":"/I0_1548194465894::_g_rpcReady","f":"I0_1548194465894","r":"I0_1548194465894","t":"32296067","c":1,"a":[null],"g":false}
registerServiceWorker.js:53 message=!_{"s":"__cb","f":"I0_1548194465894","r":"I0_1548194465894","t":"32296067","c":null,"a":[1,[null]],"g":false}
registerServiceWorker.js:53 message=!_{"s":"__cb","f":"I0_1548194465894","r":"I0_1548194465894","t":"32296067","c":null,"a":[2,[null]],"g":false}
registerServiceWorker.js:53 message=!_{"s":"/I0_1548194465894::_g_restyleMe","f":"I0_1548194465894","r":"I0_1548194465894","t":"32296067","c":2,"a":[{"setHideOnLeave":false}],"g":false}
registerServiceWorker.js:53 message=!_{"s":"__cb","f":"I0_1548194465894","r":"I0_1548194465894","t":"32296067","c":null,"a":[4,[null]],"g":false}
registerServiceWorker.js:53 message=!_{"s":"/I0_1548194465894::authEvent","f":"I0_1548194465894","r":"I0_1548194465894","t":"32296067","c":3,"a":[{"type":"authEvent","authEvent":{"type":"unknown","eventId":null,"urlResponse":null,"sessionId":null,"postBody":null,"tenantId":null,"error":{"code":"auth/no-auth-event","message":"An internal error has occurred."}}}],"g":false}
registerServiceWorker.js:53 message=!_{"s":"__cb","f":"I0_1548194465894","r":"I0_1548194465894","t":"32296067","c":null,"a":[3,[true]],"g":false}

我在这里做错什么了？

Answer 1

有几件事不对

1. navigator.serviceWorker.controller.postMessage('skipWaiting');

这是从window向worker发送一条消息，但您正在等待window上的消息

• 控制器->不是worker实例。postMessage()将把这个消息发送给那个工人。
• 不过，您不想向该员工发帖--这是您当前正在工作的员工，而您想通知尚未接手的新安装的员工

1. 即使您设法在message事件处理程序中运行代码，它也不会运行。

      if (messageEvent.data === 'skipWaiting') {
        console.log('skipWaiting');
        return navigator.serviceWorker.getRegistration(swUrl)
          .then(registration => registration.skipWaiting());
      }

没有registration.skipWaiting()方法。我们在skipWaiting代码中调用service-worker.js

在您的示例中，您将在工作代码中为message添加一个事件侦听器，并在那里拦截“跳跳等待”消息。

工人代码

self.addEventListener('message', (event) => {
  if (event.data == 'skipWaiting') self.skipWaiting();
});

窗口代码(仅更改)

向现在安装的员工发送一条消息，以跳过等待并接管。

console.log('>> New content is available; please refresh.');
installingWorker.postMessage('skipWaiting');