getAuthToken回调中的sendResponse不起作用

Question

I am having trouble with using sendResponse from my background script to my popup script. I have discovered that the problem concerns that I am trying to sendResponse from within the getAuthToken callback. How do I get around this?

chrome.extension.onMessage.addListener(
  function(request, sender, sendResponse) {
    if (request.task == "auth") {
      chrome.identity.getAuthToken({
        'interactive': true
      }, function(token) {
        if (chrome.runtime.lastError) {
          alert(chrome.runtime.lastError.message);
          return;
        }
      })

      var x = new XMLHttpRequest();
      x.open('GET', 'https://www.googleapis.com/oauth2/v2/userinfo?alt=json&access_token=' + token);

      x.onload = function() {
        if (x.readyState = 200) {
          var data = this.responseText;
          jsonResponse = JSON.parse(data);
          sendResponse({
            response: jsonResponse
          }); //return the email to the popup
          return true;
        };
      }
      x.send();
    }; //end of auth

Answer 1

You have to return true from the callback you pass to addListener to be able to use sendResponse from asynchronously running code. Here it is in the documentation

In the above example, sendResponse was called synchronously. If you want to asynchronously use sendResponse, add return true; to the onMessage event handler.