Google Git
Sign in
ara-mdk / platform / external / chromium / 201ade2fbba22bfb27ae029f4d23fca6ded109a0 / . / chrome / common / extensions / docs / messaging.html
blob: 4d7d884661566084bc85073462089248946c10fe [file] [log] [blame]
<!DOCTYPE html><!-- This page is a placeholder for generated extensions api doc. Note:
1) The <head> information in this page is significant, should be uniform
across api docs and should be edited only with knowledge of the
templating mechanism.
3) All <body>.innerHTML is genereated as an rendering step. If viewed in a
browser, it will be re-generated from the template, json schema and
authored overview content.
4) The <body>.innerHTML is also generated by an offline step so that this
page may easily be indexed by search engines.
--><html xmlns="http://www.w3.org/1999/xhtml"><head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<link href="css/ApiRefStyles.css" rel="stylesheet" type="text/css">
<link href="css/print.css" rel="stylesheet" type="text/css" media="print">
<script type="text/javascript" src="../../../third_party/jstemplate/jstemplate_compiled.js">
</script>
<script type="text/javascript" src="js/api_page_generator.js"></script>
<script type="text/javascript" src="js/bootstrap.js"></script>
<script type="text/javascript" src="js/sidebar.js"></script>
<title>Message Passing - Google Chrome Extensions - Google Code</title></head>
<body> <div id="gc-container" class="labs">
<div id="devModeWarning">
You are viewing extension docs in chrome via the 'file:' scheme: are you expecting to see local changes when you refresh? You'll need run chrome with --allow-file-access-from-files.
</div>
<!-- SUBTEMPLATES: DO NOT MOVE FROM THIS LOCATION -->
<!-- In particular, sub-templates that recurse, must be used by allowing
jstemplate to make a copy of the template in this section which
are not operated on by way of the jsskip="true" -->
<div style="display:none">
<!-- VALUE -->
<div id="valueTemplate">
<dt>
<var>paramName</var>
<em>
<!-- TYPE -->
<div style="display:inline">
(
<span class="optional">optional</span>
<span class="enum">enumerated</span>
<span id="typeTemplate">
<span>
<a> Type</a>
</span>
<span>
<span>
array of <span><span></span></span>
</span>
<span>paramType</span>
<span></span>
</span>
</span>
)
</div>
</em>
</dt>
<dd class="todo">
Undocumented.
</dd>
<dd>
Description of this parameter from the json schema.
</dd>
<dd>
This parameter was added in version
<b><span></span></b>.
You must omit this parameter in earlier versions,
and you may omit it in any version. If you require this
parameter, the manifest key
<a href="manifest.html#minimum_chrome_version">minimum_chrome_version</a>
can ensure that your extension won't be run in an earlier browser version.
</dd>
<!-- OBJECT PROPERTIES -->
<dd>
<dl>
<div>
<div>
</div>
</div>
</dl>
</dd>
<!-- FUNCTION PARAMETERS -->
<dd>
<div></div>
</dd>
</div> <!-- /VALUE -->
<div id="functionParametersTemplate">
<h5>Parameters</h5>
<dl>
<div>
<div>
</div>
</div>
</dl>
</div>
</div> <!-- /SUBTEMPLATES -->
<a id="top"></a>
<div id="skipto">
<a href="#gc-pagecontent">Skip to page content</a>
<a href="#gc-toc">Skip to main navigation</a>
</div>
<!-- API HEADER -->
<table id="header" width="100%" cellspacing="0" border="0">
<tbody><tr>
<td valign="middle"><a href="http://code.google.com/"><img src="images/code_labs_logo.gif" height="43" width="161" alt="Google Code Labs" style="border:0; margin:0;"></a></td>
<td valign="middle" width="100%" style="padding-left:0.6em;">
<form action="http://www.google.com/cse" id="cse" style="margin-top:0.5em">
<div id="gsc-search-box">
<input type="hidden" name="cx" value="002967670403910741006:61_cvzfqtno">
<input type="hidden" name="ie" value="UTF-8">
<input type="text" name="q" value="" size="55">
<input class="gsc-search-button" type="submit" name="sa" value="Search">
<br>
<span class="greytext">e.g. "page action" or "tabs"</span>
</div>
</form>
<script type="text/javascript" src="http://www.google.com/jsapi"></script>
<script type="text/javascript">google.load("elements", "1", {packages: "transliteration"});</script>
<script type="text/javascript" src="http://www.google.com/coop/cse/t13n?form=cse&amp;t13n_langs=en"></script>
<script type="text/javascript" src="http://www.google.com/coop/cse/brand?form=cse&amp;lang=en"></script>
</td>
</tr>
</tbody></table>
<div id="codesiteContent" class="">
<a id="gc-topnav-anchor"></a>
<div id="gc-topnav">
<h1>Google Chrome Extensions (<a href="http://code.google.com/labs/">Labs</a>)</h1>
<ul id="home" class="gc-topnav-tabs">
<li id="home_link">
<a href="index.html" title="Google Chrome Extensions home page">Home</a>
</li>
<li id="docs_link">
<a href="docs.html" title="Official Google Chrome Extensions documentation">Docs</a>
</li>
<li id="faq_link">
<a href="faq.html" title="Answers to frequently asked questions about Google Chrome Extensions">FAQ</a>
</li>
<li id="samples_link">
<a href="samples.html" title="Sample extensions (with source code)">Samples</a>
</li>
<li id="group_link">
<a href="http://groups.google.com/a/chromium.org/group/chromium-extensions" title="Google Chrome Extensions developer forum">Group</a>
</li>
</ul>
</div> <!-- end gc-topnav -->
<div class="g-section g-tpl-170">
<!-- SIDENAV -->
<div class="g-unit g-first" id="gc-toc">
<ul>
<li><a href="getstarted.html">Getting Started</a></li>
<li><a href="overview.html">Overview</a></li>
<li><a href="whats_new.html">What's New?</a></li>
<li><h2><a href="devguide.html">Developer's Guide</a></h2>
<ul>
<li>Browser UI
<ul>
<li><a href="browserAction.html">Browser Actions</a></li>
<li><a href="contextMenus.html">Context Menus</a></li>
<li><a href="notifications.html">Desktop Notifications</a></li>
<li><a href="omnibox.html">Omnibox</a></li>
<li><a href="options.html">Options Pages</a></li>
<li><a href="override.html">Override Pages</a></li>
<li><a href="pageAction.html">Page Actions</a></li>
</ul>
</li>
<li>Browser Interaction
<ul>
<li><a href="bookmarks.html">Bookmarks</a></li>
<li><a href="cookies.html">Cookies</a></li>
<li><a href="events.html">Events</a></li>
<li><a href="history.html">History</a></li>
<li><a href="management.html">Management</a></li>
<li><a href="tabs.html">Tabs</a></li>
<li><a href="windows.html">Windows</a></li>
</ul>
</li>
<li>Implementation
<ul>
<li><a href="a11y.html">Accessibility</a></li>
<li><a href="background_pages.html">Background Pages</a></li>
<li><a href="content_scripts.html">Content Scripts</a></li>
<li><a href="xhr.html">Cross-Origin XHR</a></li>
<li><a href="idle.html">Idle</a></li>
<li><a href="i18n.html">Internationalization</a></li>
<li class="leftNavSelected">Message Passing</li>
<li><a href="npapi.html">NPAPI Plugins</a></li>
</ul>
</li>
<li>Finishing
<ul>
<li><a href="hosting.html">Hosting</a></li>
<li><a href="external_extensions.html">Other Deployment Options</a></li>
</ul>
</li>
</ul>
</li>
<li><h2><a href="apps.html">Packaged Apps</a></h2></li>
<li><h2><a href="tutorials.html">Tutorials</a></h2>
<ul>
<li><a href="tut_debugging.html">Debugging</a></li>
<li><a href="tut_analytics.html">Google Analytics</a></li>
<li><a href="tut_oauth.html">OAuth</a></li>
</ul>
</li>
<li><h2>Reference</h2>
<ul>
<li>Formats
<ul>
<li><a href="manifest.html">Manifest Files</a></li>
<li><a href="match_patterns.html">Match Patterns</a></li>
</ul>
</li>
<li><a href="permission_warnings.html">Permission Warnings</a></li>
<li><a href="api_index.html">chrome.* APIs</a></li>
<li><a href="api_other.html">Other APIs</a></li>
</ul>
</li>
<li><h2><a href="samples.html">Samples</a></h2></li>
<div class="line"> </div>
<li><h2>More</h2>
<ul>
<li><a href="http://code.google.com/chrome/webstore/docs/index.html">Chrome Web Store</a></li>
<li><a href="http://code.google.com/chrome/apps/docs/developers_guide.html">Hosted Apps</a></li>
<li><a href="themes.html">Themes</a></li>
</ul>
</li>
</ul>
</div>
<script>
initToggles();
</script>
<div class="g-unit" id="gc-pagecontent">
<div id="pageTitle">
<h1 class="page_title">Message Passing</h1>
</div>
<!-- TABLE OF CONTENTS -->
<div id="toc">
<h2>Contents</h2>
<ol>
<li>
<a href="#simple">Simple one-time requests</a>
<ol>
<li style="display: none; ">
<a>h3Name</a>
</li>
</ol>
</li><li>
<a href="#connect">Long-lived connections</a>
<ol>
<li style="display: none; ">
<a>h3Name</a>
</li>
</ol>
</li><li>
<a href="#external">Cross-extension messaging</a>
<ol>
<li style="display: none; ">
<a>h3Name</a>
</li>
</ol>
</li><li>
<a href="#security-considerations">Security considerations</a>
<ol>
<li style="display: none; ">
<a>h3Name</a>
</li>
</ol>
</li><li>
<a href="#examples">Examples</a>
<ol>
<li style="display: none; ">
<a>h3Name</a>
</li>
</ol>
</li>
<li style="display: none; ">
<a href="#apiReference">API reference</a>
<ol>
<li>
<a href="#properties">Properties</a>
<ol>
<li>
<a href="#property-anchor">propertyName</a>
</li>
</ol>
</li>
<li>
<a href="#methods">Methods</a>
<ol>
<li>
<a href="#method-anchor">methodName</a>
</li>
</ol>
</li>
<li>
<a href="#events">Events</a>
<ol>
<li>
<a href="#event-anchor">eventName</a>
</li>
</ol>
</li>
<li>
<a href="#types">Types</a>
<ol>
<li>
<a href="#id-anchor">id</a>
</li>
</ol>
</li>
</ol>
</li>
</ol>
</div>
<!-- /TABLE OF CONTENTS -->
<!-- Standard content lead-in for experimental API pages -->
<p id="classSummary" style="display: none; ">
For information on how to use experimental APIs, see the <a href="experimental.html">chrome.experimental.* APIs</a> page.
</p>
<!-- STATIC CONTENT PLACEHOLDER -->
<div id="static"><div id="pageData-name" class="pageData">Message Passing</div>
<div id="pageData-showTOC" class="pageData">true</div>
<p>
Since content scripts run in the context of a web page and not the extension,
they often need some way of communicating with the rest of the extension. For
example, an RSS reader extension might use content scripts to detect the
presence of an RSS feed on a page, then notify the background page in order to
display a page action icon for that page.
</p><p>
Communication between extensions and their content scripts works by using
message passing. Either side can listen for messages sent from the other end,
and respond on the same channel. A message can contain any valid JSON object
(null, boolean, number, string, array, or object). There is a simple API for
<a href="#simple">one-time requests</a>
and a more complex API that allows you to have
<a href="#connect">long-lived connections</a>
for exchanging multiple messages with a shared context. It is also possible to
send a message to another extension if you know its ID, which is covered in
the
<a href="#external">cross-extension messages</a>
section.
</p><h2 id="simple">Simple one-time requests</h2>
<p>
If you only need to send a single message to another part of your extension
(and optionally get a response back), you should use the simplified
<a href="extension.html#method-sendRequest">chrome.extension.sendRequest()</a>
or
<a href="tabs.html#method-sendRequest">chrome.tabs.sendRequest()</a>
methods. This lets you send a one-time JSON-serializable message from a
content script to extension, or vice versa, respectively. An optional
callback parameter allows you handle the response from the other side, if
there is one.
</p><p>
Sending a request from a content script looks like this:
</p><pre>contentscript.js
================
chrome.extension.sendRequest({greeting: "hello"}, function(response) {
console.log(response.farewell);
});
</pre>
<p>
Sending a request from the extension to a content script looks very similar,
except that you need to specify which tab to send it to. This example
demonstrates sending a message to the content script in the selected tab.
</p><pre>background.html
===============
chrome.tabs.getSelected(null, function(tab) {
chrome.tabs.sendRequest(tab.id, {greeting: "hello"}, function(response) {
console.log(response.farewell);
});
});
</pre>
<p>
On the receiving end, you need to set up an
<a href="extension.html#event-onRequest">chrome.extension.onRequest</a>
event listener to handle the message. This looks the same from a content
script or extension page. The request will remain open until you call
sendResponse, so it is good practice to call sendResponse with an empty
object to allow the request to be cleaned up.
</p><pre>chrome.extension.onRequest.addListener(
function(request, sender, sendResponse) {
console.log(sender.tab ?
"from a content script:" + sender.tab.url :
"from the extension");
if (request.greeting == "hello")
sendResponse({farewell: "goodbye"});
else
sendResponse({}); // snub them.
});
</pre>
<p class="note">
<b>Note:</b> If multiple pages are listening for onRequest events, only the
first to call sendResponse() for a particular event will succeed in sending the
response. All other responses to that event will be ignored.
</p>
<h2 id="connect">Long-lived connections</h2>
<p>
Sometimes it's useful to have a conversation that lasts longer than a single
request and response. In this case, you can open a long-lived channel from
your content script to an extension page, or vice versa, using
<a href="extension.html#method-connect">chrome.extension.connect()</a>
or
<a href="tabs.html#method-connect">chrome.tabs.connect()</a> respectively. The
channel can optionally have a name, allowing you to distinguish between
different types of connections.
</p><p>
One use case might be an automatic form fill extension. The content script
could open a channel to the extension page for a particular login, and send a
message to the extension for each input element on the page to request the
form data to fill in. The shared connection allows the extension to keep
shared state linking the several messages coming from the content script.
</p><p>
When establishing a connection, each end is given a
<a href="extension.html#type-Port">Port</a>
object which is used for sending and receiving messages through that
connection.
</p><p>
Here is how you open a channel from a content script, and send and listen for
messages:
</p><pre>contentscript.js
================
var port = chrome.extension.connect({name: "knockknock"});
port.postMessage({joke: "Knock knock"});
port.onMessage.addListener(function(msg) {
if (msg.question == "Who's there?")
port.postMessage({answer: "Madame"});
else if (msg.question == "Madame who?")
port.postMessage({answer: "Madame... Bovary");
});
</pre>
<p>
Sending a request from the extension to a content script looks very similar,
except that you need to specify which tab to connect to. Simply replace the
call to connect in the above example with
<a href="tabs.html#method-connect">chrome.tabs.connect(tabId, {name:
"knockknock"})</a>.
</p><p>
In order to handle incoming connections, you need to set up a
<a href="extension.html#event-onConnect">chrome.extension.onConnect</a>
event listener. This looks the same from a content script or an extension
page. When another part of your extension calls "connect()", this event is
fired, along with the
<a href="extension.html#type-Port">Port</a>
object you can use to send and receive messages through the connection. Here's
what it looks like to respond to incoming connections:
</p><pre>chrome.extension.onConnect.addListener(function(port) {
console.assert(port.name == "knockknock");
port.onMessage.addListener(function(msg) {
if (msg.joke == "Knock knock")
port.postMessage({question: "Who's there?"});
else if (msg.answer == "Madame")
port.postMessage({question: "Madame who?"});
else if (msg.answer == "Madame... Bovary")
port.postMessage({question: "I don't get it."});
});
});
</pre>
<p>
You may want to find out when a connection is closed, for example if you are
maintaining separate state for each open port. For this you can listen to the
<a href="extension.html#type-Port">Port.onDisconnect</a>
event. This event is fired either when the other side of the channel manually
calls
<a href="extension.html#type-Port">Port.disconnect()</a>, or when the page
containing the port is unloaded (for example if the tab is navigated).
onDisconnect is guaranteed to be fired only once for any given port.
</p><h2 id="external">Cross-extension messaging</h2>
<p>
In addition to sending messages between different components in your
extension, you can use the messaging API to communicate with other extensions.
This lets you expose a public API that other extensions can take advantage of.
</p><p>
Listening for incoming requests and connections is similar to the internal
case, except you use the
<a href="extension.html#event-onRequestExternal">chrome.extension.onRequestExternal</a>
or
<a href="extension.html#event-onConnectExternal">chrome.extension.onConnectExternal</a>
methods. Here's an example of each:
</p><pre>// For simple requests:
chrome.extension.onRequestExternal.addListener(
function(request, sender, sendResponse) {
if (sender.id == blacklistedExtension)
sendResponse({}); // don't allow this extension access
else if (request.getTargetData)
sendResponse({targetData: targetData});
else if (request.activateLasers) {
var success = activateLasers();
sendResponse({activateLasers: success});
}
});
// For long-lived connections:
chrome.extension.onConnectExternal.addListener(function(port) {
port.onMessage.addListener(function(msg) {
// See other examples for sample onMessage handlers.
});
});
</pre>
<p>
Likewise, sending a message to another extension is similar to sending one
within your extension. The only difference is that you must pass the ID of the
extension you want to communicate with. For example:
</p><pre>// The ID of the extension we want to talk to.
var laserExtensionId = "abcdefghijklmnoabcdefhijklmnoabc";
// Make a simple request:
chrome.extension.sendRequest(laserExtensionId, {getTargetData: true},
function(response) {
if (targetInRange(response.targetData))
chrome.extension.sendRequest(laserExtensionId, {activateLasers: true});
});
// Start a long-running conversation:
var port = chrome.extension.connect(laserExtensionId);
port.postMessage(...);
</pre>
<h2 id="security-considerations">Security considerations</h2>
<p>
When receiving a message from a content script or another extension, your
background page should be careful not to fall victim to <a href="http://en.wikipedia.org/wiki/Cross-site_scripting">cross-site
scripting</a>. Specifically, avoid using dangerous APIs such as the
below:
</p>
<pre>background.html
===============
chrome.tabs.sendRequest(tab.id, {greeting: "hello"}, function(response) {
// WARNING! Might be evaluating an evil script!
var resp = eval("(" + response.farewell + ")");
});
background.html
===============
chrome.tabs.sendRequest(tab.id, {greeting: "hello"}, function(response) {
// WARNING! Might be injecting a malicious script!
document.getElementById("resp").innerHTML = response.farewell;
});
</pre>
<p>
Instead, prefer safer APIs that do not run scripts:
</p>
<pre>background.html
===============
chrome.tabs.sendRequest(tab.id, {greeting: "hello"}, function(response) {
// JSON.parse does not evaluate the attacker's scripts.
var resp = JSON.parse(response.farewell);
});
background.html
===============
chrome.tabs.sendRequest(tab.id, {greeting: "hello"}, function(response) {
// innerText does not let the attacker inject HTML elements.
document.getElementById("resp").innerText = response.farewell;
});
</pre>
<h2 id="examples">Examples</h2>
<p>
You can find simple examples of communication via messages in the
<a href="http://src.chromium.org/viewvc/chrome/trunk/src/chrome/common/extensions/docs/examples/api/messaging/">examples/api/messaging</a>
directory.
Also see the
<a href="http://src.chromium.org/viewvc/chrome/trunk/src/chrome/common/extensions/docs/examples/howto/contentscript_xhr">contentscript_xhr</a> example,
in which a content script and its parent extension exchange messages,
so that the parent extension can perform
cross-site requests on behalf of the content script.
For more examples and for help in viewing the source code, see
<a href="samples.html">Samples</a>.
</p>
</div>
<!-- API PAGE -->
<div class="apiPage" style="display: none; ">
<a name="apiReference"></a>
<h2>API reference: chrome.apiname </h2>
<!-- PROPERTIES -->
<div class="apiGroup">
<a name="properties"></a>
<h3 id="properties">Properties</h3>
<div>
<a></a>
<h4>getLastError</h4>
<div class="summary">
<!-- Note: intentionally longer 80 columns -->
<span>chrome.extension</span><span>lastError</span>
</div>
<div>
</div>
</div>
</div> <!-- /apiGroup -->
<!-- METHODS -->
<div class="apiGroup" id="methods">
<a name="methods"></a>
<h3>Methods</h3>
<!-- iterates over all functions -->
<div class="apiItem">
<a></a> <!-- method-anchor -->
<h4>method name</h4>
<div class="summary"><span>void</span>
<!-- Note: intentionally longer 80 columns -->
<span>chrome.module.methodName</span>(<span><span>, </span><span></span>
<var><span></span></var></span>)</div>
<div class="description">
<p class="todo">Undocumented.</p>
<p>
A description from the json schema def of the function goes here.
</p>
<!-- PARAMETERS -->
<h4>Parameters</h4>
<dl>
<div>
<div>
</div>
</div>
</dl>
<!-- RETURNS -->
<h4>Returns</h4>
<dl>
<div>
<div>
</div>
</div>
</dl>
<!-- CALLBACK -->
<div>
<div>
<h4>Callback function</h4>
<p>
The callback <em>parameter</em> should specify a function
that looks like this:
</p>
<p>
If you specify the <em>callback</em> parameter, it should
specify a function that looks like this:
</p>
<!-- Note: intentionally longer 80 columns -->
<pre>function(<span>Type param1, Type param2</span>) <span class="subdued">{...}</span>;</pre>
<dl>
<div>
<div>
</div>
</div>
</dl>
</div>
</div>
<!-- MIN_VERSION -->
<p>
This function was added in version <b><span></span></b>.
If you require this function, the manifest key
<a href="manifest.html#minimum_chrome_version">minimum_chrome_version</a>
can ensure that your extension won't be run in an earlier browser version.
</p>
</div> <!-- /description -->
</div> <!-- /apiItem -->
</div> <!-- /apiGroup -->
<!-- EVENTS -->
<div class="apiGroup">
<a name="events"></a>
<h3 id="events">Events</h3>
<!-- iterates over all events -->
<div class="apiItem">
<a></a>
<h4>event name</h4>
<div class="summary">
<!-- Note: intentionally longer 80 columns -->
<span class="subdued">chrome.bookmarks</span><span>onEvent</span><span class="subdued">.addListener</span>(function(<span>Type param1, Type param2</span>) <span class="subdued">{...}</span>);
</div>
<div class="description">
<p class="todo">Undocumented.</p>
<p>
A description from the json schema def of the event goes here.
</p>
<!-- PARAMETERS -->
<h4>Parameters</h4>
<dl>
<div>
<div>
</div>
</div>
</dl>
</div> <!-- /decription -->
</div> <!-- /apiItem -->
</div> <!-- /apiGroup -->
<!-- TYPES -->
<div class="apiGroup">
<a name="types"></a>
<h3 id="types">Types</h3>
<!-- iterates over all types -->
<div class="apiItem">
<a></a>
<h4>type name</h4>
<div>
</div>
</div> <!-- /apiItem -->
</div> <!-- /apiGroup -->
</div> <!-- /apiPage -->
</div> <!-- /gc-pagecontent -->
</div> <!-- /g-section -->
</div> <!-- /codesiteContent -->
<div id="gc-footer" --="">
<div class="text">
<p>
Except as otherwise <a href="http://code.google.com/policies.html#restrictions">noted</a>,
the content of this page is licensed under the <a rel="license" href="http://creativecommons.org/licenses/by/3.0/">Creative Commons
Attribution 3.0 License</a>, and code samples are licensed under the
<a rel="license" href="http://code.google.com/google_bsd_license.html">BSD License</a>.
</p>
<p>
©2010 Google
</p>
<!-- begin analytics -->
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript"></script>
<script src="http://www.google-analytics.com/ga.js" type="text/javascript"></script>
<script type="text/javascript">
// chrome doc tracking
try {
var engdocs = _gat._getTracker("YT-10763712-2");
engdocs._trackPageview();
} catch(err) {}
// code.google.com site-wide tracking
try {
_uacct="UA-18071-1";
_uanchor=1;
_uff=0;
urchinTracker();
}
catch(e) {/* urchinTracker not available. */}
</script>
<!-- end analytics -->
</div>
</div> <!-- /gc-footer -->
</div> <!-- /gc-container -->
</body></html>