1page.title=Metrics and Grids 2page.tags="layout","screens" 3@jd:body 4 5<p>Devices vary not only in physical size, but also in screen density (<acronym title="Dots per 6inch">DPI</acronym>). To simplify the way you design for multiple screens, think of each device as 7falling into a particular size bucket and density bucket. The size buckets are <em>handset</em> (smaller than 8600<acronym title="Density-independent pixels. One dp is one pixel on a 160 dpi 9screen.">dp</acronym>) and <em>tablet</em> (larger than or equal 600dp). The density buckets are <acronym 10title="Low density (120 dpi)">LDPI</acronym>, <acronym title="Medium density (160 11dpi)">MDPI</acronym>, <acronym title="High density (240 dpi)">HDPI</acronym>, and <acronym title 12="Extra-high density (320 dpi)">XHDPI</acronym>. Optimize your application's UI by designing 13alternative layouts for some of the different size buckets, and provide alternative bitmap images 14for different density buckets.</p> 15 16<div class="layout-content-row"> 17 <div class="layout-content-col span-8"> 18 19 <img src="{@docRoot}design/media/metrics_diagram.png"> 20 21 </div> 22 <div class="layout-content-col span-5"> 23 24<h4>Space considerations</h4> 25<p>Devices vary in the amount of density-independent pixels (dp) they can display.</p> 26<p>To see more, visit the 27<a href="http://developer.android.com/resources/dashboard/screens.html" target="_blank"> 28Screen Sizes and Densities Device Dashboard</a>.</p> 29 30 </div> 31</div> 32 33<h2 id="48dp-rhythm">48dp Rhythm</h2> 34 35<p>Touchable UI components are generally laid out along 48dp units.</p> 36 37<img src="{@docRoot}design/media/metrics_48.png"> 38 39<div class="vspace size-2"> </div> 40 41<h4>Why 48dp?</h4> 42<p>On average, 48dp translate to a physical size of about 9mm (with some variability). This is 43comfortably in the range of recommended target sizes (7-10 mm) for touchscreen objects and users 44will be able to reliably and accurately target them with their fingers.</p> 45<p>If you design your elements to be at least 48dp high and wide you can guarantee that:</p> 46<ul> 47<li>your targets will never be smaller than the minimum recommended target size of 7mm regardless of 48 what screen they are displayed on.</li> 49<li>you strike a good compromise between overall information density on the one hand, and 50 targetability of UI elements on the other.</li> 51</ul> 52 53<img src="{@docRoot}design/media/metrics_closeup.png"> 54 55<div class="vspace size-2"> </div> 56 57<h4>Mind the gaps</h4> 58<p>Spacing between each UI element is 8dp.</p> 59 60<h2 id="examples">Examples</h2> 61 62<img src="{@docRoot}design/media/metrics_forms.png"> 63
