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copied!<p>It seems like when a script has already been injected it is not injected again.<br> So, the way to go would be to initiate your action by passing a message to the content script. (Of course, if the content script has not been injected yet, you need to inject it first.)</p> <p>One solution I came up with (and after testing confirmed it works fine) is the following:</p> <ol> <li><p>On <code>pageAction.onClicked</code> send a message from the background page to the content script, asking it to do something (e.g. post the grades). Also, request a response to be sent back to the background page.<br> [See, also, <strong><a href="http://developer.chrome.com/extensions/tabs.html#method-sendMessage" rel="nofollow">chrome.tabs.sendMessage(...)</a></strong>.]</p></li> <li><p>If the content script has already been injected, have it receive the message, send a confirmation back to the background page and proceed doing something (e.g. posting the grades). This process can take place as many times as you want.<br> [See, also, <strong><a href="http://developer.chrome.com/extensions/runtime.html#event-onMessage" rel="nofollow">chrome.runtime.onMessage</a></strong>.]</p></li> <li><p>The first time that the <code>pageAction.onClicked</code> is fired, there will be no content script listening for messages. In that case, there will be no message confirmation. Instead <strong><a href="http://developer.chrome.com/extensions/runtime.html#property-lastError" rel="nofollow">chrome.runtime.lastError</a></strong> will be set. In that case, the background page will have to inject the content script first and then send the message again.<br> [See, also, <strong><a href="http://developer.chrome.com/extensions/runtime.html#property-lastError" rel="nofollow">chrome.runtime.lastError</a></strong>.]</p></li> </ol> <hr> <p>Theoreticaly speaking, that should do it !<br> Practicaly, this is the sample code that worked for me:</p> <p><strong>manifest.json</strong>: (Note: If you have more specific requirements regarding the pages you need to access, you could incorporate them into the manifest and get rid of some of the permissions.)</p> <pre><code>{ ... "background": { "persistent": false, "scripts": ["background.js"] }, "page_action": { "default_title": "Test Extension" }, "permissions": [ "tabs", "http://*/*", "https://*/*" ] ... } </code></pre> <p><strong>background.js:</strong></p> <pre><code>function checkForValidURL(tabId, info, tab) { var idx = tab.url.indexOf("tiger.armstrong"); if (idx > 0) { chrome.pageAction.show(tabId); } else { chrome.pageAction.hide(tabId); } } chrome.tabs.onUpdated.addListener(checkForValidURL); function onPageActionClicked(tab) { // Send message to content script, asking to post grades alert("Calling content_script..."); chrome.tabs.sendMessage(tab.id, { action: "postGrades" }, function() { if (chrome.runtime.lastError) { // The error indicates that the content script // has not been injected yet. Inject it and... chrome.tabs.executeScript(tab.id, { file: "content.js" }, function() { if (!chrome.runtime.lastError) { // ...if injected successfully, send the message anew onPageActionClicked(tab); } }); } else { // The content script called our response callback, // confirming that it is there and got our message alert("Message got through !"); } }); }; chrome.pageAction.onClicked.addListener(onPageActionClicked); </code></pre> <p><strong>content.js:</strong></p> <pre><code>var livelabtools = { /** * This function is like window.open, but it can POST (rather than GET) from * JS source: http://canop.org/blog/?p=426 */ canop_open: function (method, url, data, target) { var form = document.createElement("form"); form.action = url; form.method = method; form.target = target || "_self"; // 'data' is an object with key-value pairs // of fields to be sent if (data) { for (var key in data) { var input = document.createElement("input"); input.name = key; input.value = (typeof(data[key]) === "object") ? JSON.stringify(data[key]) : data[key]; form.appendChild(input); } } form.submit(); form.remove(); }, post_grades: function () { console.log("Posting some grades..."); livelabtools.canop_open("POST", "http://aspen2.cscofc.info/jsontocsv.php", "{}"); console.log("Grades sent !"); } } // Listen for messages from the background page // (It actually listens for messages from anyone in the context, // but the background page is the one that interrests us) chrome.runtime.onMessage.addListener(function(msg, sender, response) { // If we've been asked to post grades... if (msg.action && (msg.action == "postGrades")) { // ...confirm we got the message and... response(); // ...do what we do best: post grades ! livelabtools.post_grades(); } }); </code></pre> <hr> <p>Let's hope this covers it :)</p>

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