向后台脚本发送消息

Question

我正在尝试实现一个屏幕共享网络应用程序，该应用程序将使用 desktopCapture Chrome API 在网页上显示用户屏幕。我已经创建了 chrome 扩展并在后台运行了一个事件侦听器。我的问题是当我尝试从网页向扩展发送消息（以获取 userMedia id）时，我在扩展端没有收到任何内容。我还尝试将 getUserMedia id 返回到网页以显示提要。我已经附上了我所拥有的。谢谢

清单

{
"name": "Class Mate Manifest",
"description": "Extension that allows for user to share their screen",
"version": "1",
"manifest_version": 2,

"background": {
  "scripts": ["background.js"]
},
"permissions": [
"desktopCapture",
"tabs"
],
"browser_action": {
  "default_icon": "icon.png",
"default_popup": "index.html"
    }
 }

background.js

chrome.runtime.onMessage.addListener(
function(request, sender, sendResponse) {
console.log(request.greeting);
if(request.greeting == yes){
 chrome.desktopCapture.chooseDesktopMedia(["screen", "window"], sendResponse);
 return true;
 }
 });

网页.js

function gotStream(stream) {
console.log("Received local stream");
var video = document.querySelector("video");
video.src = URL.createObjectURL(stream);
localstream = stream;
// stream.onended = function() { console.log("Ended"); };
}

function getUserMediaError() {
console.log("getUserMedia() failed.");
}

function onAccessApproved(id) {
console.log(id);
if (!id) {
console.log("Access rejected.");
return;
}


navigator.webkitGetUserMedia({
  audio:false,
  video: { mandatory: { chromeMediaSource: "desktop", chromeMediaSourceId: id } }
}, gotStream, getUserMediaError);

}


chrome.runtime.sendMessage({greeting: "yes"}, onAccessApproved);

Answer 1

您不能像在任意网页代码的内容脚本中使用消息一样简单地使用消息传递。

文档中有两个与网页通信的指南，分别对应两种方式：(externally_connectable)(custom events with a content script)

假设您想允许http://example.com 向您的分机发送消息。

1. 您需要在清单中专门将该网站列入白名单：

     "externally_connectable" : {
       matches: [ "http://example.com" ]
     },
   

2. 您需要obtain a permanent extension ID。假设生成的 ID 是abcdefghijklmnoabcdefhijklmnoabc

3. 您的网页需要检查是否允许发送消息，然后使用预定义的 ID 发送消息：

   // Website code
   // This will only be true if some extension allowed the page to connect
   if(chrome && chrome.runtime && chrome.runtime.sendMessage) {
     chrome.runtime.sendMessage(
       "abcdefghijklmnoabcdefhijklmnoabc",
       {greeting: "yes"},
       onAccessApproved
     );
   }
   

4. 您的扩展程序需要收听外部消息并且可能还要检查它们的来源：

   // Extension's background code
   chrome.runtime.onMessageExternal.addListener(
     function(request, sender, sendResponse) {
       if(!validate(request.sender)) // Check the URL with a custom function
         return;
       /* do work */
     }
   );