1 page.title=Metrics and Grids 2 page.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 6 inch">DPI</acronym>). To simplify the way you design for multiple screens, think of each device as 7 falling into a particular size bucket and density bucket:</p> 8 <ul> 9 <li>The size buckets are <em>handset</em> (smaller than 10 600<acronym title="Density-independent pixels: One dp is one pixel on a 160 dpi (mdpi) 11 screen.">dp</acronym>) and <em>tablet</em> (larger than or equal 600dp).</li> 12 <li>The density buckets are <acronym 13 title="Low density (120 dpi)">LDPI</acronym>, <acronym title="Medium density (160 14 dpi)">MDPI</acronym>, <acronym title="High density (240 dpi)">HDPI</acronym>, <acronym title 15 ="Extra-high density (320 dpi)">XHDPI</acronym>, <acronym title 16 ="Extra-extra!-high density (480 dpi)">XXHDPI</acronym>, and <acronym title 17 ="Extra-extra-extra!-high density (640 dpi)">XXXHDPI</acronym>.</li> 18 </ul> 19 20 <p>Optimize your application's UI by designing 21 alternative layouts for some of the different size buckets, and provide alternative bitmap images 22 for different density buckets.</p> 23 24 <p>Because it's important that you design and implement your layouts for multiple densities, 25 the guidelines below and throught the documentation 26 refer to layout dimensions with <acronym title="Density-independent pixels: One dp is one pixel 27 on a 160 dpi (mdpi) screen.">dp</acronym> measurements instead of pixels.</p> 28 29 30 <div class="layout-content-row"> 31 <div class="layout-content-col span-8"> 32 33 <img src="{@docRoot}design/media/metrics_diagram.png"> 34 35 </div> 36 <div class="layout-content-col span-5"> 37 38 <h4>Space considerations</h4> 39 <p>Devices vary in the amount of density-independent pixels (dp) they can display.</p> 40 <p>To see more, visit the 41 <a href="http://developer.android.com/resources/dashboard/screens.html" target="_blank"> 42 Screen Sizes and Densities Device Dashboard</a>.</p> 43 44 </div> 45 </div> 46 47 48 <h2 id="48dp-rhythm">48dp Rhythm</h2> 49 50 <p>Touchable UI components are generally laid out along 48dp units.</p> 51 52 <img src="{@docRoot}design/media/metrics_48.png"> 53 54 <div class="vspace size-2"> </div> 55 56 <h4>Why 48dp?</h4> 57 <p>On average, 48dp translate to a physical size of about 9mm (with some variability). This is 58 comfortably in the range of recommended target sizes (7-10 mm) for touchscreen objects and users 59 will be able to reliably and accurately target them with their fingers.</p> 60 <p>If you design your elements to be at least 48dp high and wide you can guarantee that:</p> 61 <ul> 62 <li>your targets will never be smaller than the minimum recommended target size of 7mm regardless of 63 what screen they are displayed on.</li> 64 <li>you strike a good compromise between overall information density on the one hand, and 65 targetability of UI elements on the other.</li> 66 </ul> 67 68 <img src="{@docRoot}design/media/metrics_closeup.png"> 69 70 <div class="vspace size-2"> </div> 71 72 <h4>Mind the gaps</h4> 73 <p>Spacing between each UI element is 8dp.</p> 74 75 <h2 id="examples">Examples</h2> 76 77 <img src="{@docRoot}design/media/metrics_forms.png"> 78
