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PODownload file from FileSystem in Google Chrome
 

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    <p>I've created an app for Google Chrome that stores a file into the File System. I can read this file but every time I try to export it, it doesn't work. I've tried some methods:</p> <ul> <li>method toUrl, </li> <li><blockquote> <p><a href="https://stackoverflow.com/questions/3749231/download-file-using-javascript-jquery">Download File Using Javascript/jQuery</a></p> </blockquote></li> <li><blockquote> <p><a href="https://stackoverflow.com/questions/7160720/create-a-file-using-javascript-in-chrome-on-client-side">create a file using javascript in chrome on client side</a></p> </blockquote></li> </ul> <p>but they doesn't work.</p> <p><a href="https://stackoverflow.com/questions/16402696/replacement-for-fileentry-tourl-in-chrome-packaged-apps">Replacement for fileEntry.toURL() in Chrome Packaged Apps</a> talks about my problem.. So I changed my code into</p> <pre><code>function readFileRdf() { window.requestFileSystem(window.PERSISTENT, 5*1024*1024, function(filesystem) { fs = filesystem; fs.root.getFile('rdf.txt', {create: false}, function(fileEntry) { // Get a File object representing the file, // then use FileReader to read its contents. fileEntry.file(function(file) { var reader = new FileReader(); reader.onloadend = function(e) { fromFileSystemRdf = e.target.result; arr = fromFileSystemRdf; exportRdf(arr); }; reader.readAsText(file); }, errorHandler); }, errorHandler); }); } </code></pre> <p>and </p> <pre><code>function exportRdf(arr){ console.log(arr); chrome.fileSystem.chooseEntry({type: 'saveFile'}, function(writableFileEntry) { writableFileEntry.createWriter(function(writer) { writer.onerror = errorHandler; writer.onwriteend = function(e) { console.log('write complete'); }; console.log(arr); writer.write(new Blob([arr], {type: 'text/plain'})); }, errorHandler); }); } </code></pre> <p>the last problem is that I get an error with <strong>createWriter</strong></p> <p><em>Error in response to fileSystem.chooseEntry: TypeError: Cannot call method 'createWriter' of undefined</em></p> <p>Up.. adding a console.log(chrome.runtime.lastError); it says</p> <p><em>Object {message: "Invalid calling page. This function can't be called from a background page."}</em> </p> <p>Question solved. Since is not possible to call a method from a background page, I've used this solution: (Remember, Google Chrome doesn't accept inline javascript)</p> <p>button for exporting is pressed</p> <pre><code>`document.getElementById("button2").addEventListener("click",readFileRdf);` </code></pre> <p>method readFileRdf creates a new page:</p> <pre><code>function readFileRdf() { chrome.app.window.create("data.html"); } </code></pre> <p><strong>data.html</strong> calls the data.js file</p> <pre><code> &lt;!DOCTYPE html&gt; &lt;html&gt; &lt;head&gt; &lt;meta charset="utf-8"&gt; &lt;title&gt;Data page&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;/body&gt; &lt;script rel="text/javascript" src="data.js"&gt;&lt;/script&gt; &lt;/html&gt; </code></pre> <p>and <strong>data.js</strong> allows the user to read the file from filesystem and download it </p> <pre><code>window.requestFileSystem = window.requestFileSystem || window.webkitRequestFileSystem; function initFs() { window.requestFileSystem(window.PERSISTENT, 5*1024*1024, function(filesystem) { fs = filesystem; readFile(fs); }, errorHandler); } function readFile(fs) { fs.root.getFile('rdf.txt', {create: false}, function(fileEntry) { // Get a File object representing the file, // then use FileReader to read its contents. fileEntry.file(function(file) { var reader = new FileReader(); reader.onloadend = function(e) { fromFileSystemRdf = e.target.result; arr = fromFileSystemRdf; exportRdf(arr); }; reader.readAsText(file); }, errorHandler); }, errorHandler); } function exportRdf(arr){ console.log(arr); chrome.fileSystem.chooseEntry({type: 'saveFile'}, function(writableFileEntry) { console.log(chrome.runtime.lastError); writableFileEntry.createWriter(function(writer) { writer.onerror = errorHandler; writer.onwriteend = function(e) { console.log('write complete'); }; writer.write(new Blob([arr], {type: 'text/plain'})); }, errorHandler); }); } initFs(); </code></pre>
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