1page.title=Best Practices for Web Apps 2@jd:body 3 4<style> 5.bold li { 6 font-weight:bold; 7} 8.bold li * { 9 font-weight:normal; 10} 11</style> 12 13<p>Developing web pages and web applications for mobile devices presents a different set of 14challenges compared to developing a web page for the typical 15desktop web browser. To help you get started, the following is a list of practices you should 16follow in order to provide the most effective web application for Android and other mobile 17devices.</p> 18 19<ol class="bold"> 20 21<li>Redirect mobile devices to a dedicated mobile version of your web site 22 <p>There are several ways you can redirect requests to the mobile version of your web site, using 23server-side redirects. Most often, this is done by "sniffing" the User Agent 24string provided by the web browser. To determine whether to serve a mobile version of your site, you 25should simply look for the "mobile" string in the User Agent, which matches a wide variety of mobile 26devices. If necessary, you can also identify the specific operating system in the User Agent string 27(such as "Android 2.1").</p> 28 <p class="note"><strong>Note:</strong> Large screen Android-powered devices that should be served 29full-size web sites (such as tablets) do <em>not</em> include the "mobile" string in the user agent, 30while the rest of the user agent string is mostly the same. As such, it's important that you deliver 31the mobile version of your web site based on whether the "mobile" string exists in the user 32agent.</p> 33</li> 34 35 36<li>Use a valid markup DOCTYPE that's appropriate for mobile devices 37 <p>The most common markup language used for mobile web sites is <a 38href="http://www.w3.org/TR/2008/REC-xhtml-basic-20080729/">XHTML Basic</a>. This standard 39ensures specific markup for your web site that works best on mobile devices. For instance, it does 40not allow HTML frames or nested tables, which perform poorly on mobile devices. Along with the 41DOCTYPE, be sure to declare the appropriate character encoding for the document (such as 42UTF-8).</p> 43 <p>For example:</p> 44<pre> 45<?xml version="1.0" encoding="UTF-8"?> 46<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.1//EN" 47 "http://www.w3.org/TR/xhtml-basic/xhtml-basic11.dtd"> 48</pre> 49 50 <p>Also be sure that your web page markup is valid against the declared DOCTYPE. Use a 51validator, such as the one available at 52<a href="http://validator.w3.org/">http://validator.w3.org</a>.</p> 53</li> 54 55 56<li>Use viewport meta data to properly resize your web page 57 <p>In your document {@code <head>}, you should provide meta data that specifies how you 58want the browser's viewport to render your web page. For example, your viewport meta data can 59specify the height and width for the browser's viewport, the initial web page scale and even the 60target screen density.</p> 61 <p>For example:</p> 62<pre> 63<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no"> 64</pre> 65 <p>For more information about how to use viewport meta data for Android-powered devices, read <a 66href="{@docRoot}guide/webapps/targeting.html">Targeting Screens from Web Apps</a>.</p> 67</li> 68 69 70<li>Avoid multiple file requests 71 <p>Because mobile devices typically have a connection speed far slower than a desktop 72computer, you should make your web pages load as fast as possible. One way to speed it up is to 73avoid loading extra files such as stylesheets and script files in the {@code 74<head>}. Instead, provide your CSS and JavaScript directly in the <head> (or 75at the end of the <body>, for scripts that you don't need until the page is loaded). 76Alternatively, you should optimize the size and speed of your files by compressing them with tools 77like <a href="http://code.google.com/p/minify/">Minify</a>.</p> 78</li> 79 80 81<li>Use a vertical linear layout 82 <p>Avoid the need for the user to scroll left and right while navigating your web 83page. Scrolling up and down is easier for the user and makes your web page simpler.</p> 84</li> 85 86</ol> 87 88<p>For a more thorough guide to creating great mobile web applications, see the W3C's <a 89href="http://www.w3.org/TR/mobile-bp/">Mobile Web Best Practices</a>. For other guidance on 90improving the speed of your web site (for mobile and desktop), see Yahoo!'s guide to <a 91href="http://developer.yahoo.com/performance/index.html#rules">Exceptional Performance</a> and 92Google's speed tutorials in <a href="http://code.google.com/speed/articles/">Let's make the web 93faster</a>.</p> 94 95 96