1 page.title=Application Structure 2 @jd:body 3 4 <p>Apps come in many varieties that address very different needs. For example:</p> 5 <ul> 6 <li>Apps such as Calculator or Camera that are built around a single focused activity handled from a 7 single screen</li> 8 <li>Apps such as Phone whose main purpose is to switch between different activities without deeper 9 navigation</li> 10 <li>Apps such as Gmail or the Play Store that combine a broad set of data views with deep navigation</li> 11 </ul> 12 <p>Your app's structure depends largely on the content and tasks you want to surface for your users.</p> 13 <h2 id="general-structure">General Structure</h2> 14 15 <p>A typical Android app consists of top level and detail/edit views. If the navigation hierarchy is 16 deep and complex, category views connect top level and detail views.</p> 17 18 <div class="layout-content-row"> 19 <div class="layout-content-col span-9"> 20 21 <img src="{@docRoot}design/media/app_structure_overview.png"> 22 23 </div> 24 <div class="layout-content-col span-4"> 25 26 <h4>Top level views</h4> 27 <p>The top level of the app typically consists of the different views that your app supports. The views 28 either show different representations of the same data or expose an altogether different functional 29 facet of your app.</p> 30 <div class="vspace size-3"> </div> 31 32 <h4>Category views</h4> 33 <p>Category views allow you to drill deeper into your data.</p> 34 <div class="vspace size-11"> </div> 35 36 <h4>Detail/edit view</h4> 37 <p>The detail/edit view is where you consume or create data.</p> 38 39 </div> 40 </div> 41 42 <h2 id="top-level">Top Level</h2> 43 44 <p>The layout of your start screen requires special attention. This is the first screen people see 45 after launching your app, so it should be an equally rewarding experience for new and frequent 46 visitors alike.</p> 47 <p>Ask yourself: "What are my typical users most likely going to want to do in my app?", and structure 48 your start screen experience accordingly.</p> 49 50 <div class="layout-content-row"> 51 <div class="layout-content-col span-5"> 52 53 <h4>Put content forward</h4> 54 <p>Many apps focus on the content display. Avoid navigation-only screens and instead let people get to 55 the meat of your app right away by making content the centerpiece of your start screen. Choose 56 layouts that are visually engaging and appropriate for the data type and screen size.</p> 57 58 </div> 59 <div class="layout-content-col span-8"> 60 61 <img src="{@docRoot}design/media/app_structure_market.png"> 62 <div class="figure-caption"> 63 The Play Store app's start screen primarily allows navigation into the stores for Apps, Music, Books, 64 Movies and Games. It is also enriched with tailored recommendations and promotions that 65 surface content of interest to the user. Search is readily available from the action bar. 66 </div> 67 68 </div> 69 </div> 70 71 <div class="layout-content-row"> 72 <div class="layout-content-col span-5"> 73 74 <h4>Set up action bars for navigation and actions</h4> 75 <p>All screens in your app should display action bars to provide consistent navigation and surface 76 important actions.</p> 77 <p>At the top level, special considerations apply to the action bar:</p> 78 <ul> 79 <li>Use the action bar to display your app's icon or title.</li> 80 <li>If your top level consists of multiple views, or if switching between data from different user 81 accounts is a significant use case, make sure that it's easy for the user to navigate between them 82 by adding view controls to your action bar.</li> 83 <li>If your app allows people to create content, consider making the content accessible right from the 84 top level.</li> 85 <li>If your content is searchable, include the Search action in the action bar so people can cut 86 through the navigation hierarchy.</li> 87 </ul> 88 89 </div> 90 <div class="layout-content-col span-8"> 91 92 <img src="{@docRoot}design/media/app_structure_gmail.png"> 93 <div class="figure-caption"> 94 Email is about productivity, so an efficient, easy-to-skim list with higher data density works 95 well. Navigation supports switching between accounts and recent labels. Icons for creating a 96 new message or searching are prominent in the split action bar at the bottom. 97 </div> 98 99 </div> 100 </div> 101 102 <div class="layout-content-row"> 103 <div class="layout-content-col span-5"> 104 105 <h4>Create an identity for your app</h4> 106 <p>Creating an identity for your app goes beyond the action bar. Your app communicates its identity 107 through its data, the way that data is arranged, and how people interact with it. Especially for 108 media-rich applications, try to create unique layouts that showcase your data and go beyond the 109 monotony of simple list views.</p> 110 111 </div> 112 <div class="layout-content-col span-8"> 113 114 <img src="{@docRoot}design/media/app_structure_music_lndscp.png"> 115 <div class="figure-caption"> 116 The 3D carousel celebrates cover art and establishes a unique identity for the Music app. 117 Defaulting to the Recent view keeps the focus on music the user has been listening to lately. 118 </div> 119 120 </div> 121 </div> 122 123 <h2 id="categories">Categories</h2> 124 125 <p>Generally, the purpose of a deep, data-driven app is to navigate through organizational categories 126 to the detail level, where data can be viewed and managed. Minimize perceived navigation effort by 127 keeping your apps shallow.</p> 128 <p>Even though the number of vertical navigation steps from the top level down to the detail views is 129 typically dictated by the structure of your app's content, there are several ways you can cut down 130 on the perception of onerous navigation.</p> 131 <h4>Use tabs to combine category selection and data display</h4> 132 <p>This can be successful if the categories are familiar or the number of categories is small. It has 133 the advantage that a level of hierarchy is removed and data remains at the center of the user's 134 attention. Navigating laterally between data-rich categories is more akin to a casual browsing 135 experience than to an explicit navigation step.</p> 136 137 <div class="vspace size-1"> </div> 138 139 <div class="layout-content-row"> 140 <div class="layout-content-col span-8"> 141 142 <p>If the categories are familiar, predictable, or closely related, use scrolling tabs (where not all 143 items are in view simultaneously). Keep the number of scrolling tabs at a manageable level to 144 minimize navigational effort. Rule of thumb: no more than 5–7 tabs.</p> 145 146 <img src="{@docRoot}design/media/app_structure_scrolltabs.png"> 147 <div class="figure-caption"> 148 The Play Store app uses tabs to simultaneously show category choice and content. To navigate 149 between categories, users can swipe left/right on the content. 150 </div> 151 152 </div> 153 <div class="layout-content-col span-5"> 154 155 <p>If the categories in the tabs are not closely related, favor fixed tabs, so that all categories are 156 in view at the same time.</p> 157 158 <img src="{@docRoot}design/media/app_structure_fixedtabs.png"> 159 <div class="figure-caption"> 160 YouTube uses fixed tabs to switch between different, relatively unrelated functional areas. 161 </div> 162 163 164 </div> 165 </div> 166 167 <h4>Allow cutting through hierarchies</h4> 168 <p>Take advantage of shortcuts that allow people to reach their goals quicker. To allow top-level 169 invocation of actions for a data item from within list or grid views, display prominent actions 170 directly on list view items using drop-downs or split list items. This lets people invoke actions on 171 data without having to navigate all the way down the hierarchy.</p> 172 173 <img src="{@docRoot}design/media/app_structure_shortcut_on_item.png"> 174 <div class="figure-caption"> 175 Music allows the user to act upon a data item (song) from within the category view (album), 176 thereby removing the need to navigate all the way down to the song's detail view. 177 </div> 178 179 <h4>Acting upon multiple data items</h4> 180 <p>Even though category views mostly serve to guide people to content detail, keep in mind that there 181 are often good reasons to act on collections of data as well.</p> 182 <p>For example, if you allow people to delete an item in a detail view, you should also allow them to 183 delete multiple items in the category view. Analyze which detail view actions are applicable to 184 collections of items. Then use multi-select to allow application of those actions to multiple items 185 in a category view.</p> 186 <h2 id="details">Details</h2> 187 188 <p>The detail view allows you to view and act on your data. The layout of the detail view depends on 189 the data type being displayed, and therefore differs widely among apps.</p> 190 191 <div class="layout-content-row"> 192 <div class="layout-content-col span-4"> 193 194 <h4>Layout</h4> 195 <p>Consider the activities people will perform in the detail view and arrange the layout accordingly. 196 For immersive content, make use of the lights-out mode to allow for distraction-free viewing of 197 full-screen content.</p> 198 199 <img src="{@docRoot}design/media/app_structure_people_detail.png"> 200 201 </div> 202 <div class="layout-content-col span-9"> 203 204 <img src="{@docRoot}design/media/app_structure_book_detail_page_flip.png"> 205 <div class="figure-caption"> 206 Google Books' detail view is all about replicating the experience of reading an actual book. 207 The page-flip animation reinforces that notion. To create an immersive experience the app 208 enters lights-out mode, which hides all system UI affordances. 209 </div> 210 211 <div class="figure-caption"> 212 The purpose of the People app's detail view is to surface communication options. The list view 213 allows for efficient scanning and quick access of phone numbers, email addresses and other 214 information items. Split items are used to combine calling and messaging into one compact line 215 item. 216 </div> 217 </div> 218 </div> 219 220 <h4>Make navigation between detail views efficient</h4> 221 <p>If your users are likely to want to look at multiple items in sequence, allow them to navigate 222 between items from within the detail view. Use swipe views or other techniques, such as filmstrips, 223 to achieve this.</p> 224 225 <img src="{@docRoot}design/media/app_structure_gmail_swipe.png"> 226 <div class="figure-caption"> 227 Gmail using swipe views to navigate from detail view to detail view. 228 </div> 229 230 <img src="{@docRoot}design/media/app_structure_gallery_filmstrip.png"> 231 <div class="figure-caption"> 232 In addition to supporting swipe gestures to move left or right through images, Gallery provides a 233 filmstrip control that lets people quickly jump to specific images. 234 </div> 235 236 <h2 id="checklist">Checklist</h2> 237 238 <ul> 239 <li> 240 <p>Find ways to display useful content on your start screen.</p> 241 </li> 242 <li> 243 <p>Use action bars to provide consistent navigation.</p> 244 </li> 245 <li> 246 <p>Keep your hierarchies shallow by using horizontal navigation and shortcuts.</p> 247 </li> 248 <li> 249 <p>Use multi-select to allow the user to act on collections of data.</p> 250 </li> 251 <li> 252 <p>Allow for quick navigation between detail items with swipe views.</p> 253 </li> 254 </ul> 255
