javascript - Service Worker 安装成功后更新 UI

Question

看起来 Service Worker 在工作线程上下文中运行，并且无法访问 DOM。但是，一旦安装了 Service Worker，我希望我的用户知道该应用程序现在可以离线工作。我怎样才能做到这一点？

Answer 1

当 Service Worker 处于激活状态时，这是显示 Toast“内容已缓存以供离线使用”的最佳时机。在注册您的 Service Worker 时尝试以下代码。

if ('serviceWorker' in navigator) {
  navigator.serviceWorker.register('/service-worker.js').then(function(reg) {
    // updatefound is fired if service-worker.js changes.
    reg.onupdatefound = function() {
      var installingWorker = reg.installing;

      installingWorker.onstatechange = function() {
        switch (installingWorker.state) {
          case '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 the page's interface.
              console.log('New or updated content is available.');
            } 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 now available offline!');
            }
            break;

          case 'redundant':
            console.error('The installing service worker became redundant.');
            break;
        }
      };
    };
  }).catch(function(e) {
    console.error('Error during service worker registration:', e);
  });
}