diff options
Diffstat (limited to 'docs/html/design/patterns/actionbar.jd')
| -rw-r--r-- | docs/html/design/patterns/actionbar.jd | 354 |
1 files changed, 354 insertions, 0 deletions
diff --git a/docs/html/design/patterns/actionbar.jd b/docs/html/design/patterns/actionbar.jd new file mode 100644 index 0000000..2226fec --- /dev/null +++ b/docs/html/design/patterns/actionbar.jd @@ -0,0 +1,354 @@ +page.title=Action Bar +@jd:body + +<img src="{@docRoot}design/media/action_bar_pattern_overview.png"> + +<p>The <em>action bar</em> is arguably the most important structural element of an Android app. It's a +dedicated piece of real estate at the top of each screen that is generally persistent throughout the +app.</p> +<p><strong>The main purpose of the action bar is to</strong>:</p> +<ul> +<li>Make important actions (such as <em>New</em> or <em>Search</em>, etc) prominent and accessible in a predictable + way.</li> +<li>Support consistent navigation and view switching within apps.</li> +<li>Reduce clutter by providing an action overflow for rarely used actions.</li> +<li>Provide a dedicated space for giving your app an identity.</li> +</ul> +<p>If you're new to writing Android apps, note that the action bar is one of the most important design +elements you can implement. Following the guidelines described here will go a long way toward making +your app's interface consistent with the core Android apps.</p> +<h2 id="organization">General Organization</h2> + +<p>The action bar is split into four different functional areas that apply to most apps.</p> +<img src="{@docRoot}design/media/action_bar_basics.png"> + +<div class="layout-content-row"> + <div class="layout-content-col span-7 with-callouts"> + + <ol> + <li class="value-1"><h4>App icon</h4> + <p> + +The app icon establishes your app's identity. It can be replaced with a different logo or branding +if you wish. +Important: If the app is currently not displaying the top-level screen, be sure to display the Up +caret to the left of the app icon, so the user can navigate up the hierarchy. For more discussion of +Up navigation, see the <a href="{@docRoot}design/patterns/navigation.html">Navigation</a> pattern. + +<div class="figure"> + <img src="{@docRoot}design/media/action_bar_pattern_up_app_icon.png"> + <div class="figure-caption"> + App icon with and without "up" affordance. + </div> +</div> + + </p> + </li> + </ol> + + </div> + <div class="layout-content-col span-6 with-callouts"> + + <ol> + <li class="value-2"><h4>View control</h4> + <p> + +If your app displays data in different views, this segment of the action bar allows users to switch +views. Examples of view-switching controls are drop-down menus or tab controls. + + </p> + <p> + +If your app doesn't support different views, you can also use this space to display non-interactive +content, such as an app title or longer branding information. + + </p> + </li> + <li class="value-3"><h4>Action buttons</h4> + <p> + +Show the most important actions of your app in the actions section. Actions that don't fit in the +action bar are moved automatically to the action overflow. + + </p> + </li> + <li class="value-4"><h4>Action overflow</h4> + <p> + +Move less often used actions to the action overflow. + + </p> + </li> + </ol> + </div> +</div> + +<h2 id="adapting-rotation">Adapting to Rotation and Different Screen Sizes</h2> + +<p>One of the most important UI issues to consider when creating an app is how to adjust to screen +rotation on different screen sizes.</p> +<p>You can adapt to such changes by using <em>split action bars</em>, which allow you to distribute action bar +content across multiple bars located below the main action bar or at the bottom of the screen.</p> + +<img src="{@docRoot}design/media/action_bar_pattern_rotation.png"> +<div class="figure-caption"> + Split action bar showing action buttons at the bottom of the screen in vertical orientation. +</div> + +<h2 id="considerations-split-action-bars">Layout Considerations for Split Action Bars</h2> + +<div class="layout-content-row"> + <div class="layout-content-col span-8 with-callouts"> + +<p>When splitting up content across multiple action bars, you generally have three possible locations +for action bar content:</p> +<ol> +<li><strong>Main action bar</strong></li> +<li><strong>Top bar</strong></li> +<li><strong>Bottom bar</strong></li> +</ol> +<p>If the user can navigate up the hierarchy from a given screen, the main action bar contains the up +caret, at a minimum.</p> +<p>To allow the user to quickly switch between the views your app provides, use tabs or a spinner in +the top bar.</p> +<p>To display actions and, if necessary, the action overflow, use the bottom bar.</p> + + </div> + <div class="layout-content-col span-3"> + + <img src="{@docRoot}design/media/action_bar_pattern_considerations.png"> + + </div> +</div> + +<h2 id="contextual">Contextual Action Bars</h2> + +<p>A <em>contextual action bar (CAB)</em> is a temporary action bar that overlays the app's action bar for the +duration of a particular sub-task. CABs are most typically used for tasks that involve acting on +selected data or text.</p> + +<img src="{@docRoot}design/media/action_bar_cab.png"> +<div class="figure-caption"> + Contextual action bar shown in Browser and Gmail +</div> + +<p>The selection CAB appears after a long press on a selectable data item triggers selection mode.</p> +<p><strong>From here the user can</strong>:</p> +<ul> +<li>Select additional elements by touching them.</li> +<li>Trigger an action from the CAB that applies to all selected data items. The CAB then + automatically dismisses itself.</li> +<li>Dismiss the CAB via the navigation bar's Back button or the CAB's checkmark button. This removes + the CAB along with all selection highlights.</li> +</ul> +<p>Use CABs whenever you allow the user to select data via long press. You can control the action +content of a CAB in order to insert the actions you would like the user to be able to perform.</p> +<p>For more information, refer to the "Selection" pattern.</p> +<h2 id="elements">Action Bar Elements</h2> + +<h4>Tabs</h4> +<p><em>Tabs</em> display app views concurrently and make it easy to explore and switch between them. Use tabs +if you expect your users to switch views frequently.</p> + +<img src="{@docRoot}design/media/tabs_youtube.png"> + +<p>There are two types of tabs: fixed and scrollable.</p> + +<div class="layout-content-row"> + <div class="layout-content-col span-6"> + +<h4>Scrollable tabs</h4> +<p><em>Scrollable tabs</em> always take up the entire width of the bar, with the currently active view item in +the center, and therefore need to live in a dedicated bar. Scrollable tabs can themselves be +scrolled horizontally to bring more tabs into view.</p> +<p>Use scrollable tabs if you have a large number of views or if you're unsure how many views will be +displayed because your app inserts views dynamically (for example, open chats in a messaging app +that the user can navigate between). Scrollable tabs should always allow the user to navigate +between the views by swiping left or right on the content area as well as swiping the tabs +themselves.</p> + + </div> + <div class="layout-content-col span-7"> + + <video width="400" class="with-shadow play-on-hover" autoplay> + <source src="{@docRoot}design/media/tabs_scrolly.mp4" type="video/mp4"> + <source src="{@docRoot}design/media/tabs_scrolly.webm" type="video/webm"> + <source src="{@docRoot}design/media/tabs_scrolly.ogv" type="video/ogg"> + </video> + <div class="figure-caption"> + Scrolling tabs in the Play Store app. + <div class="video-instructions"> </div> + </div> + + </div> +</div> + +<div class="layout-content-row"> + <div class="layout-content-col span-6"> + +<h4>Fixed tabs</h4> +<p><em>Fixed tabs</em> are always visible on the screen, and can't be moved out of the way like scrollable +tabs. Fixed tabs in the main action bar can move to the top bar when the screen orientation changes.</p> + + </div> + <div class="layout-content-col span-7"> + + <img src="{@docRoot}design/media/action_bar_pattern_default_tabs.png"> + <div class="figure-caption"> + Default fixed tabs shown in Holo Dark & Light. + </div> + + </div> +</div> + +<div class="layout-content-row"> + <div class="layout-content-col span-6"> + +<h4>Spinners</h4> +<p>A <em>spinner</em> is a drop-down menu that allows users to switch between views of your app. </p> +<p><strong>Use spinners rather than tabs in the main action bar if</strong>:</p> +<ul> +<li>You don't want to give up the vertical screen real estate for a dedicated tab bar.</li> +<li>You expect your app's users to switch views infrequently.</li> +</ul> + + </div> + <div class="layout-content-col span-7"> + + <img src="{@docRoot}design/media/action_bar_pattern_spinner.png"> + <div class="figure-caption"> + Action bar spinner from Calendar application. + </div> + + </div> +</div> + +<h4>Action buttons</h4> +<p><em>Action buttons</em> on the action bar surface your app's most important activities. Think about which +buttons will get used most often, and order them accordingly. Depending on available screen real +estate, the system shows your most important actions as action buttons and moves the rest to the +action overflow. The action bar and the action overflow should only present actions to the user that +are available. If an action is unavailable in the current context, hide it. Do not show it as +disabled.</p> + +<img src="{@docRoot}design/media/action_bar_pattern_action_icons.png"> +<div class="figure-caption"> + A sampling of action buttons used throughout the Gmail application. +</div> + +<p>For guidance on prioritizing actions, use the FIT scheme.</p> + +<div class="layout-content-row"> + <div class="layout-content-col span-4"> + +<p><strong>F — Frequent</strong></p> +<ul> +<li>Will people use this action at least 7 out of 10 times they visit the screen?</li> +<li>Will they typically use it several times in a row?</li> +<li>Would taking an extra step every time truly be burdensome?</li> +</ul> + + </div> + <div class="layout-content-col span-4"> + +<p><strong>I — Important</strong></p> +<ul> +<li>Do you want everyone to discover this action because it's especially cool or a selling point?</li> +<li>Is it something that needs to be effortless in the rare cases it's needed?</li> +</ul> + + </div> + <div class="layout-content-col span-4"> + +<p><strong>T — Typical</strong></p> +<ul> +<li>Is it typically presented as a first-class action in similar apps?</li> +<li>Given the context, would people be surprised if it were buried in the action overflow?</li> +</ul> + + </div> +</div> + +<p>If either F, I, or T apply, then it's appropriate for the action bar. Otherwise, it belongs in the +action overflow.</p> + +<p> + +Pre-defined glyphs should be used for certain common actions such as "refresh" and "share." The +download link below provides a package with icons that are scaled for various screen densities and +are suitable for use with the Holo Light and Holo Dark themes. The package also includes unstyled +icons that you can modify to match your theme, in addition to Adobe® Illustrator® source +files for further customization. + +</p> +<p> + +<a href="https://dl-ssl.google.com/android/design/Android_Design_Icons_20120229.zip">Download the Action Bar Icon Pack</a> + +</p> + +<div class="layout-content-row"> + <div class="layout-content-col span-6"> + +<h4>Action overflow</h4> +<p>The action overflow in the action bar provides access to your app's less frequently used actions. +The overflow icon only appears on phones that have no menu hardware keys. Phones with menu keys +display the action overflow when the user presses the key.</p> + + </div> + <div class="layout-content-col span-7"> + + <img src="{@docRoot}design/media/action_bar_pattern_overflow.png"> + <div class="figure-caption"> + Action overflow is pinned to the right side. + </div> + + </div> +</div> + +<p>How many actions will fit in the main action bar? Action bar capacity is controlled by the following +rules:</p> +<ul> +<li>Action buttons in the main action bar may not occupy more than 50% of the bar's width. Action + buttons on bottom action bars can use the entire width.</li> +<li>The screen width in density-independent pixels + (<acronym title="Density-independent pixels. One dp is one pixel on a 160 dpi screen.">dp</acronym>) + determine the number of items that will fit in the main action bar:<ul> +<li>smaller than 360 dp = 2 icons</li> +<li>360-499 dp = 3 icons</li> +<li>500-599 dp = 4 icons</li> +<li>600 dp and larger = 5 icons</li> +</ul> +</li> +</ul> + +<img src="{@docRoot}design/media/action_bar_pattern_table.png"> +<div class="figure-caption"> + In the above table "o" denotes an action bar item and "=" an overflow icon. +</div> + +<h4>Sharing data</h4> +<p>Whenever your app permits sharing of data, such as images or movie clips, use a <em>share action +provider</em> in your action bar. The share action provider is designed to speed up sharing by +displaying the most recently used sharing service next to a spinner button that contains other +sharing options.</p> + +<img src="{@docRoot}design/media/action_bar_pattern_share_pack.png"> +<div class="figure-caption"> + The Gallery app's share action provider with extended spinner for additional sharing options. +</div> + +<h2 id="checklist">Action Bar Checklist</h2> + +<p>When planning your split action bars, ask yourself questions like these:</p> +<h4>How important is view navigation to the task?</h4> +<p>If view navigation is very important to your app, use tabs (for fastest view-switching) or spinners.</p> +<h4>Which of the app's actions need to be consistently available directly from the action bar, and which can be moved to the action overflow?</h4> +<p>Use the <acronym title="Frequent, Important or Typical">FIT</acronym> scheme to decide if actions +are displayed at the top-level or can be moved to the action overflow. If the number of top-level +actions exceeds the capacity of the main action bar, display them separately in a bottom action bar.</p> +<h4>What else is important enough to warrant continuous display?</h4> +<p>Sometimes it is important to display contextual information for your app that's always visible. +Examples are the number of unread messages in a messaging inbox view or the Now Playing information +in a music player. Carefully plan which important information you would like to display and +structure your action bars accordingly.</p> |