内容脚本无法从后台脚本接收消息

Question

我尝试将消息从后台脚本发送到Chrome扩展程序中的内容脚本。但内容脚本似乎永远不会得到消息。

这是我的代码：

background.js

所以基本上我想每秒向活动标签的内容脚本发送一条消息。

'use strict';

var timeSpentToday = 0;
var timeSpentTotal = 0;
var today = (new Date()).getDate(); // today's day, to track day changing
var mainTimerId; // 1s timer that will update timeSpentToday every second

mainTimerId = setInterval(updateTime, 1000);

// function to be run every second
function updateTime() {

  ++timeSpentToday;
  ++timeSpentTotal;

  console.log(timeSpentToday);

  chrome.tabs.query({active: true, currentWindow: true}, function(tabs){
    if (tabs.length > 0) {
      console.log(tabs)
      chrome.tabs.sendMessage(tabs[0].id, {method: "sendTimeSpentToday", timeSpentToday: timeSpentToday}, function() {
        console.log('message sent')
      });  
    }
  });

  // check if we've changed day, and if it's the case, reset timeSpentToday to 0
  if ((new Date()).getDate() != today) {
    today = (new Date()).getDate();
    timeSpentToday = 0;
  }


}

content.js

console.log('Content script running.');
chrome.runtime.onMessage.addListener(function(request, sender, sendResponse) {
  console.log(request);
  if (request.method == 'sendTimeSpentToday') {

    var timeSpentToday = request.timeSpentToday;
    console.log(timeSpentToday);

    // update time label with hh:mm:ss format
    var hours = parseInt( timeSpentToday / 3600 ) % 24;
    var minutes = parseInt( timeSpentToday / 60 ) % 60;
    var seconds = timeSpentToday % 60;
    var hhmmss = (hours < 10 ? '0' + hours : hours) + ':' + (minutes < 10 ? '0' + minutes : minutes) + ':' + (seconds  < 10 ? '0' + seconds : seconds);
    document.getElementById('sf-timelabel').innerHTML = hhmmss;
  }
}

内容脚本正在运行，我看到＆＃39; Content脚本正在运行＆＃39;在我的活动标签控制台中。后台脚本也正常运行，我看到timeSpentToday每秒都会在扩展程序的控制台中被记录，并且“＆＃39;”消息已发送到＆＃39;消息也是。

请注意，我还在background.js内记录了查询的标签页。我得到一个带有一个Tab对象的数组（活动选项卡）：

Array[1]
  0: Object
    active: true
    audible: false
    height: 646
    highlighted: true
    id: 3635incognito: false
    index: 2
    mutedInfo: Object
    pinned: false
    selected: true
    status: "complete"
    width: 1332
    windowId: 36
    __proto__: Object
   length: 1
 __proto__: Array[0]

我只是不明白为什么sendMessage没有将消息发送到正确的内容脚本，或者为什么内容脚本没有收到消息。