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SEE 2009: Improving Mobile Web Developer Experience
 

SEE 2009: Improving Mobile Web Developer Experience

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This talk will provide strategies to identify common developer pitfalls for web developers developing on a mobile platform. It will include code fragments for implementing AJAX requests for a social ...

This talk will provide strategies to identify common developer pitfalls for web developers developing on a mobile platform. It will include code fragments for implementing AJAX requests for a social networking application and how to avoid frequent developer pitfalls when displaying the data retrieved on the mobile device. It will further provide coding strategies for improving performance and reducing footprint when developing on a mobile device utilizing Web technologies such as JavaScript, CSS and HTML.

This talk will conclude highlighting the activities of the Symbian Foundation including a roadmap of how the Symbian tools are being evolved to further improve and enhance the mobile Web developer experience.

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    SEE 2009: Improving Mobile Web Developer Experience SEE 2009: Improving Mobile Web Developer Experience Presentation Transcript

    • SEE 2009 Improving Mobile Web Developer Experience Tasneem Sayeed Technical Lead, Web Tools Platforms October 27, 2009
    • Outline  Definition of Mobile Web  Mobile Device Constraints  Mobile Development Challenges  SEE 2009 Widget Demo Walkthrough  Sending AJAX Requests and Retrieving Data  Performance Rules & Mobile Web Development Strategies  Bridging the Mobile Web Tools Gap  Conclusion Copyright © 2009 Symbian Foundation. 2
    • Definition of the Mobile Web “Mobile Web”  W3C pushing the idea of “One Web”  Making the same information and services available to users irrespective of the device they are using  Does not mean exactly the same information is available in exactly the same representation across all devices  The context of mobile use, device capability variations, bandwidth issues and mobile network capabilities all affect the representation  Some services and information better suited for and targeted at particular user contexts Source: W3C Mobile best practices „One Web‟ page Copyright © 2009 Symbian Foundation. 3
    • Mobile Device Constraints • Screen Size/Resolution • Keep Layout as simple and fluid as possible • Keep your page contents all in a single column stacked on top of each other so regardless of screen size/resolution, information simply wraps • Test with and without CSS and JavaScript Copyright © 2009 Symbian Foundation. 4
    • Mobile Device Constraints • Limited Memory • Limits amount of processing that can be handled • Limited battery power • Limits implementations of JavaScript, Flash and other technologies • Drains battery • Creates a slower user experience • Increases the bandwidth (i.e. can be more costly to download web content) Copyright © 2009 Symbian Foundation. 5
    • Mobile Web Development Challenges Copyright © 2009 Symbian Foundation. 6
    • Mobile Web Development Challenges • “Code once, run anywhere” is a foreign concept • Many browser and device types to accommodate • Unresolved connectivity and caching issues to contend • On our 5th Generation of HTML with WML, XHTML, and cHTML still alive • Constellation of mobile platforms • Symbian (Symbian OS-based) • Java ME • BREW • Windows Mobile • Blackberry • iPhone (Objective-C based) • Linux-based Android • Palm Web OS • and more on the way! Copyright © 2009 Symbian Foundation. 7
    • Web Technologies for Symbian Copyright © 2009 Symbian Foundation. 8
    • Web Technologies • Web Runtime (WRT) for S60 devices • A set of components based on the WebKit architecture that enables you to apply your skills at creating web content – to create full mobile web applications that are simple, powerful and optimized for mobile devices • Widget development is simplified with plug-ins for Aptana Studio, Adobe Dreamweaver, and Microsoft Visual Studio • The plug-ins enable developers to create, edit, test, package and deploy widgets all from within their web development tool of their choice For more information:: http://www.forum.nokia.com/Technology_Topics/Web_Technologies/Web_Runtime/ / See Mobile 2.0 Developer Talk on “Developing Web Runtime Widgets with Aptana” Copyright © 2009 Symbian Foundation. 9
    • SEE 2009 Demo Walkthrough Demo source code based on SEE 2009 Widget developed by Ivan Litovski, Symbian Foundation Copyright © 2009 Symbian Foundation. 10
    • SEE 2009 Widget Demo – index.html <head> <title></title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <script type="text/javascript“ src="WRTKit/WRTKit.js"></script> <script type="text/javascript" src="main.js"></script> <script type="text/javascript" src="utils.js"></script> <script type="text/javascript" src="autoupdate.js"></script> <script type="text/javascript" src="session.js"></script> <script type="text/javascript" src="schedule.js"></script> <script type="text/javascript" src="twitter.js"></script> <link rel="stylesheet" href="WRTKit/Resources/UI.css“ id="stylesheet"> <link rel="stylesheet" href="style.css" type="text/css"> </head> <body onload="javascript:init();" onShow="javascript:SetViewMode();“ onResize="javascript:SetViewMode();" > <div id="main" style="margin: 0px 0px; padding: 0px 0px; border: none; overflow: hidden;"></div> <div id="mini" style="margin: 0px 0px; padding: 0px 0px; border: none; overflow: hidden;"></div> </body> Copyright © 2009 Symbian Foundation. 11
    • SEE 2009 Widget Demo – main.js function init() { if (window.widget) { widget.setNavigationEnabled(false); menu.showSoftkeys(); var updateMenuItem = new MenuItem("Check for updates", 0); updateMenuItem.onSelect = CheckForUpdates; menu.append(updateMenuItem); // wrt bug fix setInterval("if ( IsHSViewMode() ) UpdateMiniView();", 30000); } // create UI manager uiManager = new UIManager(document.getElementById("main")); : : twitterView = new ListView(null, "<img style='margin: 0px 0px; padding: 0px 0px; border: none‘ src='home.png'>"); schedule = new Schedule(); schedule.Init(scheduleFile, function(event){ ShowMainView(); }); if ( !window.widget ) { // for firefox / firebug testing CheckForUpdates(); } } Copyright © 2009 Symbian Foundation. 12
    • SEE 2009 Widget Demo – main.js // Called when the data is loaded function ShowMainView(){ if (mainView == null) { UpdateMiniView(); mainView = new ListView(null, header); var currentSessions = schedule.GetCurrentSessions(); if (currentSessions != null) { // todo } : : twitterView.previousView = mainView; var twitterTitle = new NavigationButton(null, "tweetz-icon.png", "<img src='tweetz.png' border=0>"); twitterTitle.addEventListener("ActionPerformed", function(event){ if ( twitter == null ) { twitter = new Twitter(twitterView); } twitter.Update(10); twitterView.show(); }); mainView.addControl(twitterTitle); //twitter = new Twitter(mainView); //twitter.Update(10); mainView.previousView = null; } mainView.show(); } Copyright © 2009 Symbian Foundation. 13
    • Sending AJAX Requests and Retrieving Data using Nokia WRT Copyright © 2009 Symbian Foundation. 14
    • Update Twitter Status using WRT Twitter.prototype.Update = function(numToShow){ this.numToShow = numToShow; if ( this.buttons == null ) { // add the separator var separator = new NavigationButton(null, "tweetz-icon.png", "<img src='tweetz.png' border=0>"); separator.setEnabled(false); this.parentView.addControl(separator); // create buttons this.buttons = new Array(); for( var i = 0 ; i < this.numToShow; i++ ) { var button = new NavigationButton("twitter_button_"+i, null , ""); this.parentView.addControl(button); this.buttons.push(button); } this.buttons[0].setText("Loading twitter feed..."); } Copyright © 2009 Symbian Foundation. 15
    • Sending AJAX Requests using Twitter API // Twitter API for getting a user’s RSS feed var twitterurl = "http://twitter.com/statuses/user_timeline/TwitMyMobile.rss"; // Get the rss feed // Prepare for asynchronous download this.http = new Ajax(); // true means asynchronous request this.http.open("GET", twitterurl , true); // When the AJAX request is done, it will call self.DoUpdate() this.http.onreadystatechange = function() { self.DoUpdate(); }; // send the AJAX request this.http.send(null); Copyright © 2009 Symbian Foundation. 16
    • Parsing the RSS Data: DoUpdate() Twitter.prototype.DoUpdate = function(){ if (this.http.readyState == 4) { try { // Get parsed Doc var xmlDoc = this.http.responseXML; if (xmlDoc == null) { // if the content type is not set correctly, // we get the response as text var xmlparser = new DOMParser(); xmlDoc = xmlparser.parseFromString(this.http.responseText, "text/xml"); } var itemElements = xmlDoc.getElementsByTagName("item"); var loopEnd = Math.min(this.numToShow, itemElements.length); // traverse elements and create buttons for (var i = 0; i < loopEnd; i++) { // iterate through child nodes of this item // and gather tweets var title = null; var date = null; Copyright © 2009 Symbian Foundation. 17
    • Parsing the RSS Data: DoUpdate() node = itemElements[i].firstChild; while (node != null) { if (node.nodeType == Node.ELEMENT_NODE){ if (node.nodeName == "title") { // item title title = getTextOfNode(node); } else if (node.nodeName == "pubDate" || node.nodeName == "dc:date") { // item publishing date date = getTextOfNode(node); } } end while node = node.nextSibling; } // end for this.buttons[i].setText("<font size=0.6em><i>" + date + "</i> " + title + "</font>"); this.buttons[i].setImage("tweet.png"); } // end if (xmldoc == null) } // end try Copyright © 2009 Symbian Foundation. 18
    • Parsing the RSS Data: DoUpdate() catch (x) { this.buttons[0].setText( "<font size=0.6em>Uh-Oh! Tweetz not tweeting right now.</font>"); for (var i = 0; i < this.numToShow; i++) { this.buttons[i].setText(""); this.buttons[i].setImage(null); } // end for } // end catch } // if (this.http.readyState == 4) { } Copyright © 2009 Symbian Foundation. 19
    • Parsing the data: getTextofNode() // Returns the text of a node. function getTextOfNode(node) { var buf = ""; // iterate through all child elements and // collect all text to the buffer var child = node.firstChild; while (child != null) { if (child.nodeType == Node.TEXT_NODE || child.nodeType == Node.CDATA_SECTION_NODE) { // append text to buffer if (buf != "") { buf += " "; } buf += child.nodeValue; } child = child.nextSibling; } // make link if there is a url var ind = buf.indexOf("http://"); var endind = buf.indexOf(" ", ind); if ( ind != -1 ) { var tmp = buf.substring(0,ind); var url = ""; Copyright © 2009 Symbian Foundation. 20
    • Parsing the data: getTextofNode() if ( endind == -1 ) { url = buf.substring(ind); } else { url = buf.substring(ind, endind); } tmp += "<div class="FeedItemLink">"; tmp += "<a href="JavaScript:void(0)" onclick="openURL('" + url + "'); return false;">"; tmp += url + "</a></div>"; if ( endind != -1 ) { tmp += buf.substring(endind); } buf = tmp; } return buf; } Copyright © 2009 Symbian Foundation. 21
    • Performance Rules Copyright © 2009 Symbian Foundation. 22
    • 14 Performance Rules (Yahoo) content 1. Make Fewer HTTP Requests 2. Use a Content Delivery Network server server 3. Add an Expires Header (or Cache-control) server 4. GZip Components CSS 5. Put CSS (Stylesheets) at the Top javascript 6. Move Scripts to the Bottom (inline too) CSS 7. Avoid CSS Expressions CSS Javascript 8. Make JavaScript and CSS External content 9. Reduce DNS Lookups 10. Minify JavaScript and CSS (inline too) CSS Javascript 11. Avoid Redirects content Javascript 12. Remove Duplicate Scripts sserver 13. Configure ETags content 14. Make AJAX Cacheable  Source: http://developer.yahoo.com/performance/rules.html Copyright © 2009 Symbian Foundation. 23
    • Performance Rules: Make Fewer HTTP Requests • Less components = fast page • HTTP Request overhead • Combine scripts • Combine CSS stylesheets • Combine images into CSS sprites Copyright © 2009 Symbian Foundation. 24
    • Performance Rules: GZip Components • When you send zipped content over the internet, the browser unpacks it • Modern browsers understand compressed content • Request header Accept-Encoding:gzip,deflate • Response header Content-Encoding: gzip • All text components should be sent gzipped: html (php), js, css, xml, txt… Copyright © 2009 Symbian Foundation. 25
    • Performance Rules: Put CSS at the Top • Firefox and IE will not render anything until the last piece of CSS reaches the wire • Place stylesheets as early as possible in the document <head> <title>Your page here</title> <link href=“styles.css” …> </head> <body> <!– content --> </body> Copyright © 2009 Symbian Foundation. 26
    • Performance Rules: Move Scripts to the Bottom (inline too) • Scripts block downloads • Since the script can do location.href or document.write at any time, browser blocks rather than downloading possibly useless components • Inline scripts too <body> <!– content --> <script src=“script.js” …/> </body> </html> Copyright © 2009 Symbian Foundation. 27
    • Performance Rules: Avoid CSS Expressions CSS expression #content { position: absolute; left: expression(document.body.offsetWidth + „px‟); } • In IE, this is the only way to have Javascript in CSS • CSS expressions tend to get executed more often than was intended, think about onmousemove • Smart expressions overwrite themselves Copyright © 2009 Symbian Foundation. 28
    • Performance Rules: Make Javascript and CSS External • Helps with caching, “never expire” policy • Share with other pages • However, this is two more HTTP requests • May want to consider inlining for homepages Copyright © 2009 Symbian Foundation. 29
    • Performance Rules: Minify JavaScript and CSS (inline too) • Minify, but still Gzip • JSMin (Written in Javascript, but has a PHP port) • YUI compressor – minifies CSS too • Inline styles and scripts should also be minified • Minification • Removes unnecessary characters from code to reduce its size, thus improving load times • When JS/CSS code is minified, all comments are usually removed as well as unnecessary “white space” characters like <space>, <newline>, and <tab> • With respect to JavaScript, this improves load time performance because the size of the file downloaded is often significantly reduced • Two Popular Tools for Minifying JavaScript code are: • JSMin • YUI Compressor To learn more on Minification tools, see MinifyJS.com and MinifyCSS.com Copyright © 2009 Symbian Foundation. 30
    • Performance Rules • Avoid Redirects • A wasted HTTP Request • Causes a Restart • Remove Duplicate Scripts • IE may decide to download them again Copyright © 2009 Symbian Foundation. 31
    • Performance Rules: Make AJAX Cacheable • Content returned from XMLHttpRequest is like any other component • Returned content must be Gzipped • Could be cached • Cache-control: max-age=? Copyright © 2009 Symbian Foundation. 32
    • Newer Performance Rules Copyright © 2009 Symbian Foundation. 33
    • 20 New Performance Rules for Faster Web Pages (Yahoo) 1. Flush the buffer early 2. Use GET for AJAX requests 3. Post-load components 4. Preload components 5. Reduce the number of DOM elements 6. Split components across domains 7. Minimize the number of iframes 8. No 404s 9. Reduce cookie size 10. Use cookie-free domains for components 11. Minimize DOM access 12. Develop smart event handlers 13. Choose <link> over @import 14. Avoid filters 15. Optimize images 16. Optimize CSS sprites 17. Don‟t scale images in HTML 18. Make favicon.ico small and cacheable 19. Keep components under 25K 20. Pack components into a multipart document Source: http://developer.yahoo.com/performance/rules.html Copyright © 2009 Symbian Foundation. 34
    • Performance Rules:Use GET for AJAX Requests • GET is for retrieving data • POST is a two-step process (send headers, send data) • GET request is one TCP packet, except in the case you have a lot of cookies • Max URL length is 2K (because of IE) • POST without actually posting data is the same as GET Source: http://developer.yahoo.com/performance/rules.html Yahoo!Mail Research) Copyright © 2009 Symbian Foundation. 35
    • Performance Rules: Post-Load Components • Determine the components absolutely required initially to render the page. • Rest of the components (i.e. drag and drop, animations, hidden content, images below the fold) can all wait • JavaScript is ideal candidate for splitting Source: http://developer.yahoo.com/performance/rules.html YUI Image Loader YUI Get Utility Copyright © 2009 Symbian Foundation. 36
    • Performance Rules: Minimize DOM Access • DOM access is the slowest • Cache • Update nodes “offline” and then add them to the tree • Avoid fixing layout with JavaScript Source: http://developer.yahoo.com/performance/rules.html Copyright © 2009 Symbian Foundation. 37
    • Performance Rules:Optimize Images • GIF – don‟t use a bigger palette than you will need • Use PNGs instead of GIFs • Use pngcrush tool (or optipng or pngoptimizer) • Remove gamma chunks which helps with cross- browser colors • Strip comments • jpegtran – lossless JPEG operations can be used to optimize and remove comments Copyright © 2009 Symbian Foundation. 38
    • Performance Rules: Do not scale images in HTML • Scaling images in HTML downloads unnecessary bytes • If you need <img width=“200” height=“200” src=“myPic.jpg” /> • Better to just have myPic.jpg 200x200 not 1000x1000 Copyright © 2009 Symbian Foundation. 39
    • Performance Rules: Keep components under 25K • Because mobile phones may generally not cache them • Uncompressed size under 25K • Minify HTML in addition to JavaScript and CSS Copyright © 2009 Symbian Foundation. 40
    • Performance Rules: Pack components into a multipart document • For UAs that support it • For example, • Email with attachments • MMS Copyright © 2009 Symbian Foundation. 41
    • Bridging the Mobile Web Tools Gap • Develop an Eclipse Plug-in for Web Development on Symbian to support Web Runtimes • Open Source Eclipse Plug-in Alpha with the below features to enable tool developer collaboration by December 2009 • Based on JSDT (part of Eclipse Web Tools Project) • Incremental Project Builder • Creates built state based on project contents, and keeps it synchronized to project changes • Integrated Debugger with basic debugging capabilities Copyright © 2009 Symbian Foundation. 42
    • Join the Symbian Community Silicon Valley Symbian Programming SIG http://www.meetup.com/Silicon-Valley-Symbian-Developers-Meetup/ Symbian SIG Mailing List Silicon-Valley-Symbian-Developers-Meetup-list@meetup.com Symbian Developer Group http://developer.symbian.org Symbian Exchange & Exposition (SEE 2009) (Oct 27-28), London, UK http://www.see2009.org/ Copyright © 2009 Symbian Foundation. 43
    • Summary • Make the experience feel like a native application • Take advantage of the enhanced features • Don‟t simply release a hybrid version of the mobile web site • Optimize performance • Collaborate with the developer community to further enhance the mobile Web development experience! Copyright © 2009 Symbian Foundation. 44
    • More Information My Blog http://mymobilecorner.blogspot.com Follow me on Twitter http://www.twitter.com/twitmymobile Symbian Developer Group http://developer.symbian.org Copyright © 2009 Symbian Foundation.