providing-resources.jd revision 1047509e49a7ec1a0fec03352d65567161a99585
1page.title=Providing Resources 2parent.title=Application Resources 3parent.link=index.html 4@jd:body 5 6<div id="qv-wrapper"> 7<div id="qv"> 8 <h2>Quickview</h2> 9 <ul> 10 <li>Different types of resources belong in different subdirectories of {@code res/}</li> 11 <li>Alternative resources provide configuration-specific resource files</li> 12 <li>Always include default resources so your app does not depend on specific 13device configurations</li> 14 </ul> 15 <h2>In this document</h2> 16 <ol> 17 <li><a href="#ResourceTypes">Grouping Resource Types</a></li> 18 <li><a href="#AlternativeResources">Providing Alternative Resources</a> 19 <ol> 20 <li><a href="#QualifierRules">Qualifier name rules</a></li> 21 <li><a href="#AliasResources">Creating alias resources</a></li> 22 </ol> 23 </li> 24 <li><a href="#Compatibility">Providing the Best Device Compatibility with Resources</a> 25 <ol> 26 <li><a href="#ScreenCompatibility">Providing screen resource compatibility for Android 271.5</a></li> 28 </ol> 29 </li> 30 <li><a href="#BestMatch">How Android Finds the Best-matching Resource</a></li> 31 <li><a href="#KnownIssues">Known Issues</a></li> 32 </ol> 33 34 <h2>See also</h2> 35 <ol> 36 <li><a href="accessing-resources.html">Accessing Resources</a></li> 37 <li><a href="available-resources.html">Resource Types</a></li> 38 <li><a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple 39Screens</a></li> 40 </ol> 41</div> 42</div> 43 44<p>You should always externalize application resources such as images and strings from your 45code, so that you can maintain them independently. You should also provide alternative resources for 46specific device configurations, by grouping them in specially-named resource directories. At 47runtime, Android uses the appropriate resource based on the current configuration. For 48example, you might want to provide a different UI layout depending on the screen size or different 49strings depending on the language setting.</p> 50 51<p>Once you externalize your application resources, you can access them 52using resource IDs that are generated in your project's {@code R} class. How to use 53resources in your application is discussed in <a href="accessing-resources.html">Accessing 54Resources</a>. This document shows you how to group your resources in your Android project and 55provide alternative resources for specific device configurations.</p> 56 57 58<h2 id="ResourceTypes">Grouping Resource Types</h2> 59 60<p>You should place each type of resource in a specific subdirectory of your project's 61{@code res/} directory. For example, here's the file hierarchy for a simple project:</p> 62 63<pre class="classic no-pretty-print"> 64MyProject/ 65 src/ <span style="color:black"> 66 MyActivity.java </span> 67 res/ 68 drawable/ <span style="color:black"> 69 icon.png </span> 70 layout/ <span style="color:black"> 71 main.xml 72 info.xml</span> 73 values/ <span style="color:black"> 74 strings.xml </span> 75</pre> 76 77<p>As you can see in this example, the {@code res/} directory contains all the resources (in 78subdirectories): an image resource, two layout resources, and a string resource file. The resource 79directory names are important and are described in table 1.</p> 80 81<p class="table-caption" id="table1"><strong>Table 1.</strong> Resource directories 82supported inside project {@code res/} directory.</p> 83 84<table> 85 <tr> 86 <th scope="col">Directory</th> 87 <th scope="col">Resource Type</th> 88 </tr> 89 90 <tr> 91 <td><code>animator/</code></td> 92 <td>XML files that define <a href="{@docRoot}guide/topics/graphics/prop-animation.html">property 93animations</a>.</td> 94 </tr> 95 96 <tr> 97 <td><code>anim/</code></td> 98 <td>XML files that define <a 99href="{@docRoot}guide/topics/graphics/view-animation.html#tween-animation">tween 100animations</a>. (Property animations can also be saved in this directory, but 101the {@code animator/} directory is preferred for property animations to distinguish between the two 102types.)</td> 103 </tr> 104 105 <tr> 106 <td><code>color/</code></td> 107 <td>XML files that define a state list of colors. See <a href="color-list-resource.html">Color 108State List Resource</a></td> 109 </tr> 110 111 <tr> 112 <td><code>drawable/</code></td> 113 <td><p>Bitmap files ({@code .png}, {@code .9.png}, {@code .jpg}, {@code .gif}) or XML files that 114are compiled into the following drawable resource subtypes:</p> 115 <ul> 116 <li>Bitmap files</li> 117 <li>Nine-Patches (re-sizable bitmaps)</li> 118 <li>State lists</li> 119 <li>Shapes</li> 120 <li>Animation drawables</li> 121 <li>Other drawables</li> 122 </ul> 123 <p>See <a href="drawable-resource.html">Drawable Resources</a>.</p> 124 </td> 125 </tr> 126 127 <tr> 128 <td><code>layout/</code></td> 129 <td>XML files that define a user interface layout. 130 See <a href="layout-resource.html">Layout Resource</a>.</td> 131 </tr> 132 133 <tr> 134 <td><code>menu/</code></td> 135 <td>XML files that define application menus, such as an Options Menu, Context Menu, or Sub 136Menu. See <a href="menu-resource.html">Menu Resource</a>.</td> 137 </tr> 138 139 <tr> 140 <td><code>raw/</code></td> 141 <td><p>Arbitrary files to save in their raw form. To open these resources with a raw 142{@link java.io.InputStream}, call {@link android.content.res.Resources#openRawResource(int) 143Resources.openRawResource()} with the resource ID, which is {@code R.raw.<em>filename</em>}.</p> 144 <p>However, if you need access to original file names and file hierarchy, you might consider 145saving some resources in the {@code 146assets/} directory (instead of {@code res/raw/}). Files in {@code assets/} are not given a 147resource ID, so you can read them only using {@link android.content.res.AssetManager}.</p></td> 148 </tr> 149 150 <tr> 151 <td><code>values/</code></td> 152 <td><p>XML files that contain simple values, such as strings, integers, and colors.</p> 153 <p>Whereas XML resource files in other {@code res/} subdirectories define a single resource 154based on the XML filename, files in the {@code values/} directory describe multiple resources. 155For a file in this directory, each child of the {@code <resources>} element defines a single 156resource. For example, a {@code <string>} element creates an 157{@code R.string} resource and a {@code <color>} element creates an {@code R.color} 158resource.</p> 159 <p>Because each resource is defined with its own XML element, you can name the file 160whatever you want and place different resource types in one file. However, for clarity, you might 161want to place unique resource types in different files. For example, here are some filename 162conventions for resources you can create in this directory:</p> 163 <ul> 164 <li>arrays.xml for resource arrays (<a 165href="more-resources.html#TypedArray">typed arrays</a>).</li> 166 <li>colors.xml for <a 167href="more-resources.html#Color">color values</a></li> 168 <li>dimens.xml for <a 169href="more-resources.html#Dimension">dimension values</a>.</li> 170 <li>strings.xml for <a href="string-resource.html">string 171values</a>.</li> 172 <li>styles.xml for <a href="style-resource.html">styles</a>.</li> 173 </ul> 174 <p>See <a href="string-resource.html">String Resources</a>, 175 <a href="style-resource.html">Style Resource</a>, and 176 <a href="more-resources.html">More Resource Types</a>.</p> 177 </td> 178 </tr> 179 180 <tr> 181 <td><code>xml/</code></td> 182 <td>Arbitrary XML files that can be read at runtime by calling {@link 183android.content.res.Resources#getXml(int) Resources.getXML()}. Various XML configuration files 184must be saved here, such as a <a 185href="{@docRoot}guide/topics/search/searchable-config.html">searchable configuration</a>. 186<!-- or preferences configuration. --></td> 187 </tr> 188</table> 189 190<p class="caution"><strong>Caution:</strong> Never save resource files directly inside the 191{@code res/} directory—it will cause a compiler error.</p> 192 193<p>For more information about certain types of resources, see the <a 194href="available-resources.html">Resource Types</a> documentation.</p> 195 196<p>The resources that you save in the subdirectories defined in table 1 are your "default" 197resources. That is, these resources define the default design and content for your application. 198However, different types of Android-powered devices might call for different types of resources. 199For example, if a device has a larger than normal screen, then you should provide 200different layout resources that take advantage of the extra screen space. Or, if a device has a 201different language setting, then you should provide different string resources that translate the 202text in your user interface. To provide these different resources for different device 203configurations, you need to provide alternative resources, in addition to your default 204resources.</p> 205 206 207<h2 id="AlternativeResources">Providing Alternative Resources</h2> 208 209 210<div class="figure" style="width:429px"> 211<img src="{@docRoot}images/resources/resource_devices_diagram2.png" height="167" alt="" /> 212<p class="img-caption"> 213<strong>Figure 1.</strong> Two different devices, each using different layout resources.</p> 214</div> 215 216<p>Almost every application should provide alternative resources to support specific device 217configurations. For instance, you should include alternative drawable resources for different 218screen densities and alternative string resources for different languages. At runtime, Android 219detects the current device configuration and loads the appropriate 220resources for your application.</p> 221 222<p>To specify configuration-specific alternatives for a set of resources:</p> 223<ol> 224 <li>Create a new directory in {@code res/} named in the form {@code 225<em><resources_name></em>-<em><config_qualifier></em>}. 226 <ul> 227 <li><em>{@code <resources_name>}</em> is the directory name of the corresponding default 228resources (defined in table 1).</li> 229 <li><em>{@code <qualifier>}</em> is a name that specifies an individual configuration 230for which these resources are to be used (defined in table 2).</li> 231 </ul> 232 <p>You can append more than one <em>{@code <qualifier>}</em>. Separate each 233one with a dash.</p> 234 <p class="caution"><strong>Caution:</strong> When appending multiple qualifiers, you must 235place them in the same order in which they are listed in table 2. If the qualifiers are ordered 236wrong, the resources are ignored.</p> 237 </li> 238 <li>Save the respective alternative resources in this new directory. The resource files must be 239named exactly the same as the default resource files.</li> 240</ol> 241 242<p>For example, here are some default and alternative resources:</p> 243 244<pre class="classic no-pretty-print"> 245res/ 246 drawable/ <span style="color:black"> 247 icon.png 248 background.png </span> 249 drawable-hdpi/ <span style="color:black"> 250 icon.png 251 background.png </span> 252</pre> 253 254<p>The {@code hdpi} qualifier indicates that the resources in that directory are for devices with a 255high-density screen. The images in each of these drawable directories are sized for a specific 256screen density, but the filenames are exactly 257the same. This way, the resource ID that you use to reference the {@code icon.png} or {@code 258background.png} image is always the same, but Android selects the 259version of each resource that best matches the current device, by comparing the device 260configuration information with the qualifiers in the resource directory name.</p> 261 262<p>Android supports several configuration qualifiers and you can 263add multiple qualifiers to one directory name, by separating each qualifier with a dash. Table 2 264lists the valid configuration qualifiers, in order of precedence—if you use multiple 265qualifiers for a resource directory, you must add them to the directory name in the order they 266are listed in the table.</p> 267 268 269<p class="table-caption" id="table2"><strong>Table 2.</strong> Configuration qualifier 270names.</p> 271<table> 272 <tr> 273 <th>Configuration</th> 274 <th>Qualifier Values</th> 275 <th>Description</th> 276 </tr> 277 <tr id="MccQualifier"> 278 <td>MCC and MNC</td> 279 <td>Examples:<br/> 280 <code>mcc310</code><br/> 281 <code><nobr>mcc310-mnc004</nobr></code><br/> 282 <code>mcc208-mnc00</code><br/> 283 etc. 284 </td> 285 <td> 286 <p>The mobile country code (MCC), optionally followed by mobile network code (MNC) 287 from the SIM card in the device. For example, <code>mcc310</code> is U.S. on any carrier, 288 <code>mcc310-mnc004</code> is U.S. on Verizon, and <code>mcc208-mnc00</code> is France on 289 Orange.</p> 290 <p>If the device uses a radio connection (GSM phone), the MCC and MNC values come 291 from the SIM card.</p> 292 <p>You can also use the MCC alone (for example, to include country-specific legal 293resources in your application). If you need to specify based on the language only, then use the 294<em>language and region</em> qualifier instead (discussed next). If you decide to use the MCC and 295MNC qualifier, you should do so with care and test that it works as expected.</p> 296 <p>Also see the configuration fields {@link 297android.content.res.Configuration#mcc}, and {@link 298android.content.res.Configuration#mnc}, which indicate the current mobile country code 299and mobile network code, respectively.</p> 300 </td> 301 </tr> 302 <tr id="LocaleQualifier"> 303 <td>Language and region</td> 304 <td>Examples:<br/> 305 <code>en</code><br/> 306 <code>fr</code><br/> 307 <code>en-rUS</code><br/> 308 <code>fr-rFR</code><br/> 309 <code>fr-rCA</code><br/> 310 etc. 311 </td> 312 <td><p>The language is defined by a two-letter <a 313href="http://www.loc.gov/standards/iso639-2/php/code_list.php">ISO 314 639-1</a> language code, optionally followed by a two letter 315 <a 316href="http://www.iso.org/iso/en/prods-services/iso3166ma/02iso-3166-code-lists/list-en1.html">ISO 317 3166-1-alpha-2</a> region code (preceded by lowercase "{@code r}"). 318 </p><p> 319 The codes are <em>not</em> case-sensitive; the {@code r} prefix is used to 320 distinguish the region portion. 321 You cannot specify a region alone.</p> 322 <p>This can change during the life 323of your application if the user changes his or her language in the system settings. See <a 324href="runtime-changes.html">Handling Runtime Changes</a> for information about 325how this can affect your application during runtime.</p> 326 <p>See <a href="localization.html">Localization</a> for a complete guide to localizing 327your application for other languages.</p> 328 <p>Also see the {@link android.content.res.Configuration#locale} configuration field, which 329indicates the current locale.</p> 330 </td> 331 </tr> 332 <tr id="LayoutDirectionQualifier"> 333 <td>Layout Direction</td> 334 <td>Examples:<br/> 335 <code>ldrtl</code><br/> 336 <code>ldltr</code><br/> 337 </td> 338 <td><p>The layout direction of your application. {@code ldrtl} means "layout-direction-right-to-left". 339 {@code ldltr} means "layout-direction-left-to-right" and is the default implicit value. 340 </p> 341 <p>This can apply to any resource like layouts or values or drawables. 342 </p> 343 <p>For example, if you want to provide some specific layout for the Arabic language and some 344 generic layout for any other "right-to-left" language (like Persian or Hebrew) then you would have: 345 </p> 346<pre class="classic no-pretty-print"> 347res/ 348 layout/ <span style="color:black"> 349 main.xml </span>(This is the default layout) 350 layout-ar/ <span style="color:black"> 351 main.xml </span>(This is the specific layout for Arabic) 352 layout-ldrtl/ <span style="color:black"> 353 main.xml </span>(This applies to any "right-to-left" language, except for Arabic, because the ar language qualifier has a higher precedence.) 354</pre> 355 </td> 356 </tr> 357 <tr id="SmallestScreenWidthQualifier"> 358 <td>smallestWidth</td> 359 <td><code>sw<N>dp</code><br/><br/> 360 Examples:<br/> 361 <code>sw320dp</code><br/> 362 <code>sw600dp</code><br/> 363 <code>sw720dp</code><br/> 364 etc. 365 </td> 366 <td> 367 <p>The fundamental size of a screen, as indicated by the shortest dimension of the available 368screen area. Specifically, the device's smallestWidth is the shortest of the screen's available 369height and width (you may also think of it as the "smallest possible width" for the screen). You can 370use this qualifier to ensure that, regardless of the screen's current orientation, your 371application's has at least {@code <N>} dps of width available for it UI.</p> 372 <p>For example, if your layout requires that its smallest dimension of screen area be at 373least 600 dp at all times, then you can use this qualifer to create the layout resources, {@code 374res/layout-sw600dp/}. The system will use these resources only when the smallest dimension of 375available screen is at least 600dp, regardless of whether the 600dp side is the user-perceived 376height or width. The smallestWidth is a fixed screen size characteristic of the device; <strong>the 377device's smallestWidth does not change when the screen's orientation changes</strong>.</p> 378 <p>The smallestWidth of a device takes into account screen decorations and system UI. For 379example, if the device has some persistent UI elements on the screen that account for space along 380the axis of the smallestWidth, the system declares the smallestWidth to be smaller than the actual 381screen size, because those are screen pixels not available for your UI. Thus, the value you use 382should be the actual smallest dimension <em>required by your layout</em> (usually, this value is the 383"smallest width" that your layout supports, regardless of the screen's current orientation).</p> 384 <p>Some values you might use here for common screen sizes:</p> 385 <ul> 386 <li>320, for devices with screen configurations such as: 387 <ul> 388 <li>240x320 ldpi (QVGA handset)</li> 389 <li>320x480 mdpi (handset)</li> 390 <li>480x800 hdpi (high density handset)</li> 391 </ul> 392 </li> 393 <li>480, for screens such as 480x800 mdpi (tablet/handset).</li> 394 <li>600, for screens such as 600x1024 mdpi (7" tablet).</li> 395 <li>720, for screens such as 720x1280 mdpi (10" tablet).</li> 396 </ul> 397 <p>When your application provides multiple resource directories with different values for 398 the smallestWidth qualifier, the system uses the one closest to (without exceeding) the 399device's smallestWidth. </p> 400 <p><em>Added in API level 13.</em></p> 401 <p>Also see the <a 402href="{@docRoot}guide/topics/manifest/supports-screens-element.html#requiresSmallest">{@code 403android:requiresSmallestWidthDp}</a> attribute, which declares the minimum smallestWidth with which 404your application is compatible, and the {@link 405android.content.res.Configuration#smallestScreenWidthDp} configuration field, which holds the 406device's smallestWidth value.</p> 407 <p>For more information about designing for different screens and using this 408qualifier, see the <a href="{@docRoot}guide/practices/screens_support.html">Supporting 409Multiple Screens</a> developer guide.</p> 410 </td> 411 </tr> 412 <tr id="ScreenWidthQualifier"> 413 <td>Available width</td> 414 <td><code>w<N>dp</code><br/><br/> 415 Examples:<br/> 416 <code>w720dp</code><br/> 417 <code>w1024dp</code><br/> 418 etc. 419 </td> 420 <td> 421 <p>Specifies a minimum available screen width, in {@code dp} units at which the resource 422 should be used—defined by the <code><N></code> value. This 423 configuration value will change when the orientation 424 changes between landscape and portrait to match the current actual width.</p> 425 <p>When your application provides multiple resource directories with different values 426 for this configuration, the system uses the one closest to (without exceeding) 427 the device's current screen width. The 428 value here takes into account screen decorations, so if the device has some 429 persistent UI elements on the left or right edge of the display, it 430 uses a value for the width that is smaller than the real screen size, accounting 431 for these UI elements and reducing the application's available space.</p> 432 <p><em>Added in API level 13.</em></p> 433 <p>Also see the {@link android.content.res.Configuration#screenWidthDp} 434 configuration field, which holds the current screen width.</p> 435 <p>For more information about designing for different screens and using this 436qualifier, see the <a href="{@docRoot}guide/practices/screens_support.html">Supporting 437Multiple Screens</a> developer guide.</p> 438 </td> 439 </tr> 440 <tr id="ScreenHeightQualifier"> 441 <td>Available height</td> 442 <td><code>h<N>dp</code><br/><br/> 443 Examples:<br/> 444 <code>h720dp</code><br/> 445 <code>h1024dp</code><br/> 446 etc. 447 </td> 448 <td> 449 <p>Specifies a minimum available screen height, in "dp" units at which the resource 450 should be used—defined by the <code><N></code> value. This 451 configuration value will change when the orientation 452 changes between landscape and portrait to match the current actual height.</p> 453 <p>When your application provides multiple resource directories with different values 454 for this configuration, the system uses the one closest to (without exceeding) 455 the device's current screen height. The 456 value here takes into account screen decorations, so if the device has some 457 persistent UI elements on the top or bottom edge of the display, it uses 458 a value for the height that is smaller than the real screen size, accounting 459 for these UI elements and reducing the application's available space. Screen 460 decorations that are not fixed (such as a phone status bar that can be 461 hidden when full screen) are <em>not</em> accounted for here, nor are 462 window decorations like the title bar or action bar, so applications must be prepared to 463 deal with a somewhat smaller space than they specify. 464 <p><em>Added in API level 13.</em></p> 465 <p>Also see the {@link android.content.res.Configuration#screenHeightDp} 466 configuration field, which holds the current screen width.</p> 467 <p>For more information about designing for different screens and using this 468qualifier, see the <a href="{@docRoot}guide/practices/screens_support.html">Supporting 469Multiple Screens</a> developer guide.</p> 470 </td> 471 </tr> 472 <tr id="ScreenSizeQualifier"> 473 <td>Screen size</td> 474 <td> 475 <code>small</code><br/> 476 <code>normal</code><br/> 477 <code>large</code><br/> 478 <code>xlarge</code> 479 </td> 480 <td> 481 <ul class="nolist"> 482 <li>{@code small}: Screens that are of similar size to a 483 low-density QVGA screen. The minimum layout size for a small screen 484 is approximately 320x426 dp units. Examples are QVGA low density and VGA high 485 density.</li> 486 <li>{@code normal}: Screens that are of similar size to a 487 medium-density HVGA screen. The minimum 488 layout size for a normal screen is approximately 320x470 dp units. Examples 489 of such screens a WQVGA low density, HVGA medium density, WVGA 490 high density.</li> 491 <li>{@code large}: Screens that are of similar size to a 492 medium-density VGA screen. 493 The minimum layout size for a large screen is approximately 480x640 dp units. 494 Examples are VGA and WVGA medium density screens.</li> 495 <li>{@code xlarge}: Screens that are considerably larger than the traditional 496 medium-density HVGA screen. The minimum layout size for an xlarge screen 497 is approximately 720x960 dp units. In most cases, devices with extra large 498 screens would be too large to carry in a pocket and would most likely 499 be tablet-style devices. <em>Added in API level 9.</em></li> 500 </ul> 501 <p class="note"><strong>Note:</strong> Using a size qualifier does not imply that the 502resources are <em>only</em> for screens of that size. If you do not provide alternative 503resources with qualifiers that better match the current device configuration, the system may use 504whichever resources are the <a href="#BestMatch">best match</a>.</p> 505 <p class="caution"><strong>Caution:</strong> If all your resources use a size qualifier that 506is <em>larger</em> than the current screen, the system will <strong>not</strong> use them and your 507application will crash at runtime (for example, if all layout resources are tagged with the {@code 508xlarge} qualifier, but the device is a normal-size screen).</p> 509 <p><em>Added in API level 4.</em></p> 510 511 <p>See <a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple 512Screens</a> for more information.</p> 513 <p>Also see the {@link android.content.res.Configuration#screenLayout} configuration field, 514which indicates whether the screen is small, normal, 515or large.</p> 516 </td> 517 </tr> 518 <tr id="ScreenAspectQualifier"> 519 <td>Screen aspect</td> 520 <td> 521 <code>long</code><br/> 522 <code>notlong</code> 523 </td> 524 <td> 525 <ul class="nolist"> 526 <li>{@code long}: Long screens, such as WQVGA, WVGA, FWVGA</li> 527 <li>{@code notlong}: Not long screens, such as QVGA, HVGA, and VGA</li> 528 </ul> 529 <p><em>Added in API level 4.</em></p> 530 <p>This is based purely on the aspect ratio of the screen (a "long" screen is wider). This 531is not related to the screen orientation.</p> 532 <p>Also see the {@link android.content.res.Configuration#screenLayout} configuration field, 533which indicates whether the screen is long.</p> 534 </td> 535 </tr> 536 <tr id="OrientationQualifier"> 537 <td>Screen orientation</td> 538 <td> 539 <code>port</code><br/> 540 <code>land</code> <!-- <br/> 541 <code>square</code> --> 542 </td> 543 <td> 544 <ul class="nolist"> 545 <li>{@code port}: Device is in portrait orientation (vertical)</li> 546 <li>{@code land}: Device is in landscape orientation (horizontal)</li> 547 <!-- Square mode is currently not used. --> 548 </ul> 549 <p>This can change during the life of your application if the user rotates the 550screen. See <a href="runtime-changes.html">Handling Runtime Changes</a> for information about 551how this affects your application during runtime.</p> 552 <p>Also see the {@link android.content.res.Configuration#orientation} configuration field, 553which indicates the current device orientation.</p> 554 </td> 555 </tr> 556 <tr id="UiModeQualifier"> 557 <td>UI mode</td> 558 <td> 559 <code>car</code><br/> 560 <code>desk</code><br/> 561 <code>television<br/> 562 <code>appliance</code> 563 </td> 564 <td> 565 <ul class="nolist"> 566 <li>{@code car}: Device is displaying in a car dock</li> 567 <li>{@code desk}: Device is displaying in a desk dock</li> 568 <li>{@code television}: Device is displaying on a television, providing 569 a "ten foot" experience where its UI is on a large screen that the 570 user is far away from, primarily oriented around DPAD or other 571 non-pointer interaction</li> 572 <li>{@code appliance}: Device is serving as an appliance, with 573 no display</li> 574 </ul> 575 <p><em>Added in API level 8, television added in API 13.</em></p> 576 <p>This can change during the life of your application if the user places the device in a 577dock. You can enable or disable some of these modes using {@link 578android.app.UiModeManager}. See <a href="runtime-changes.html">Handling Runtime Changes</a> for 579information about how this affects your application during runtime.</p> 580 </td> 581 </tr> 582 <tr id="NightQualifier"> 583 <td>Night mode</td> 584 <td> 585 <code>night</code><br/> 586 <code>notnight</code> 587 </td> 588 <td> 589 <ul class="nolist"> 590 <li>{@code night}: Night time</li> 591 <li>{@code notnight}: Day time</li> 592 </ul> 593 <p><em>Added in API level 8.</em></p> 594 <p>This can change during the life of your application if night mode is left in 595auto mode (default), in which case the mode changes based on the time of day. You can enable 596or disable this mode using {@link android.app.UiModeManager}. See <a 597href="runtime-changes.html">Handling Runtime Changes</a> for information about how this affects your 598application during runtime.</p> 599 </td> 600 </tr> 601 <tr id="DensityQualifier"> 602 <td>Screen pixel density (dpi)</td> 603 <td> 604 <code>ldpi</code><br/> 605 <code>mdpi</code><br/> 606 <code>hdpi</code><br/> 607 <code>xhdpi</code><br/> 608 <code>nodpi</code><br/> 609 <code>tvdpi</code> 610 </td> 611 <td> 612 <ul class="nolist"> 613 <li>{@code ldpi}: Low-density screens; approximately 120dpi.</li> 614 <li>{@code mdpi}: Medium-density (on traditional HVGA) screens; approximately 615160dpi.</li> 616 <li>{@code hdpi}: High-density screens; approximately 240dpi.</li> 617 <li>{@code xhdpi}: Extra high-density screens; approximately 320dpi. <em>Added in API 618Level 8</em></li> 619 <li>{@code nodpi}: This can be used for bitmap resources that you do not want to be scaled 620to match the device density.</li> 621 <li>{@code tvdpi}: Screens somewhere between mdpi and hdpi; approximately 213dpi. This is 622not considered a "primary" density group. It is mostly intended for televisions and most 623apps shouldn't need it—providing mdpi and hdpi resources is sufficient for most apps and 624the system will scale them as appropriate. This qualifier was introduced with API level 13.</li> 625 </ul> 626 <p>There is a 3:4:6:8 scaling ratio between the four primary densities (ignoring the 627tvdpi density). So, a 9x9 bitmap in ldpi is 12x12 in mdpi, 18x18 in hdpi and 24x24 in xhdpi.</p> 628 <p>If you decide that your image resources don't look good enough on a television or 629other certain devices and want to try tvdpi resources, the scaling factor is 1.33*mdpi. For 630example, a 100px x 100px image for mdpi screens should be 133px x 133px for tvdpi.</p> 631 <p class="note"><strong>Note:</strong> Using a density qualifier does not imply that the 632resources are <em>only</em> for screens of that density. If you do not provide alternative 633resources with qualifiers that better match the current device configuration, the system may use 634whichever resources are the <a href="#BestMatch">best match</a>.</p> 635 <p>See <a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple 636Screens</a> for more information about how to handle different screen densities and how Android 637might scale your bitmaps to fit the current density.</p> 638 </td> 639 </tr> 640 <tr id="TouchscreenQualifier"> 641 <td>Touchscreen type</td> 642 <td> 643 <code>notouch</code><br/> 644 <code>finger</code> 645 </td> 646 <td> 647 <ul class="nolist"> 648 <li>{@code notouch}: Device does not have a touchscreen.</li> 649 <li>{@code finger}: Device has a touchscreen that is intended to 650 be used through direction interaction of the user's finger.</li> 651 </ul> 652 <p>Also see the {@link android.content.res.Configuration#touchscreen} configuration field, 653which indicates the type of touchscreen on the device.</p> 654 </td> 655 </tr> 656 <tr id="KeyboardAvailQualifier"> 657 <td>Keyboard availability</td> 658 <td> 659 <code>keysexposed</code><br/> 660 <code>keyshidden</code><br/> 661 <code>keyssoft</code> 662 </td> 663 <td> 664 <ul class="nolist"> 665 <li>{@code keysexposed}: Device has a keyboard available. If the device has a 666software keyboard enabled (which is likely), this may be used even when the hardware keyboard is 667<em>not</em> exposed to the user, even if the device has no hardware keyboard. If no software 668keyboard is provided or it's disabled, then this is only used when a hardware keyboard is 669exposed.</li> 670 <li>{@code keyshidden}: Device has a hardware keyboard available but it is 671hidden <em>and</em> the device does <em>not</em> have a software keyboard enabled.</li> 672 <li>{@code keyssoft}: Device has a software keyboard enabled, whether it's 673visible or not.</li> 674 </ul> 675 <p>If you provide <code>keysexposed</code> resources, but not <code>keyssoft</code> 676resources, the system uses the <code>keysexposed</code> resources regardless of whether a 677keyboard is visible, as long as the system has a software keyboard enabled.</p> 678 <p>This can change during the life of your application if the user opens a hardware 679keyboard. See <a href="runtime-changes.html">Handling Runtime Changes</a> for information about how 680this affects your application during runtime.</p> 681 <p>Also see the configuration fields {@link 682android.content.res.Configuration#hardKeyboardHidden} and {@link 683android.content.res.Configuration#keyboardHidden}, which indicate the visibility of a hardware 684keyboard and and the visibility of any kind of keyboard (including software), respectively.</p> 685 </td> 686 </tr> 687 <tr id="ImeQualifier"> 688 <td>Primary text input method</td> 689 <td> 690 <code>nokeys</code><br/> 691 <code>qwerty</code><br/> 692 <code>12key</code> 693 </td> 694 <td> 695 <ul class="nolist"> 696 <li>{@code nokeys}: Device has no hardware keys for text input.</li> 697 <li>{@code qwerty}: Device has a hardware qwerty keyboard, whether it's visible to the 698user 699or not.</li> 700 <li>{@code 12key}: Device has a hardware 12-key keyboard, whether it's visible to the user 701or not.</li> 702 </ul> 703 <p>Also see the {@link android.content.res.Configuration#keyboard} configuration field, 704which indicates the primary text input method available.</p> 705 </td> 706 </tr> 707 <tr id="NavAvailQualifier"> 708 <td>Navigation key availability</td> 709 <td> 710 <code>navexposed</code><br/> 711 <code>navhidden</code> 712 </td> 713 <td> 714 <ul class="nolist"> 715 <li>{@code navexposed}: Navigation keys are available to the user.</li> 716 <li>{@code navhidden}: Navigation keys are not available (such as behind a closed 717lid).</li> 718 </ul> 719 <p>This can change during the life of your application if the user reveals the navigation 720keys. See <a href="runtime-changes.html">Handling Runtime Changes</a> for 721information about how this affects your application during runtime.</p> 722 <p>Also see the {@link android.content.res.Configuration#navigationHidden} configuration 723field, which indicates whether navigation keys are hidden.</p> 724 </td> 725 </tr> 726 <tr id="NavigationQualifier"> 727 <td>Primary non-touch navigation method</td> 728 <td> 729 <code>nonav</code><br/> 730 <code>dpad</code><br/> 731 <code>trackball</code><br/> 732 <code>wheel</code> 733 </td> 734 <td> 735 <ul class="nolist"> 736 <li>{@code nonav}: Device has no navigation facility other than using the 737touchscreen.</li> 738 <li>{@code dpad}: Device has a directional-pad (d-pad) for navigation.</li> 739 <li>{@code trackball}: Device has a trackball for navigation.</li> 740 <li>{@code wheel}: Device has a directional wheel(s) for navigation (uncommon).</li> 741 </ul> 742 <p>Also see the {@link android.content.res.Configuration#navigation} configuration field, 743which indicates the type of navigation method available.</p> 744 </td> 745 </tr> 746<!-- DEPRECATED 747 <tr> 748 <td>Screen dimensions</td> 749 <td>Examples:<br/> 750 <code>320x240</code><br/> 751 <code>640x480</code><br/> 752 etc. 753 </td> 754 <td> 755 <p>The larger dimension must be specified first. <strong>This configuration is deprecated 756and should not be used</strong>. Instead use "screen size," "wider/taller screens," and "screen 757orientation" described above.</p> 758 </td> 759 </tr> 760--> 761 <tr id="VersionQualifier"> 762 <td>Platform Version (API level)</td> 763 <td>Examples:<br/> 764 <code>v3</code><br/> 765 <code>v4</code><br/> 766 <code>v7</code><br/> 767 etc.</td> 768 <td> 769 <p>The API level supported by the device. For example, <code>v1</code> for API level 7701 (devices with Android 1.0 or higher) and <code>v4</code> for API level 4 (devices with Android 7711.6 or higher). See the <a 772href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#ApiLevels">Android API levels</a> document for more information 773about these values.</p> 774 <p class="caution"><strong>Caution:</strong> Android 1.5 and 1.6 only match resources 775with this qualifier when it exactly matches the platform version. See the section below about <a 776href="#KnownIssues">Known Issues</a> for more information.</p> 777 </td> 778 </tr> 779</table> 780 781 782<p class="note"><strong>Note:</strong> Some configuration qualifiers have been added since Android 7831.0, so not all versions of Android support all the qualifiers. Using a new qualifier implicitly 784adds the platform version qualifier so that older devices are sure to ignore it. For example, using 785a <code>w600dp</code> qualifier will automatically include the <code>v13</code> qualifier, because 786the available-width qualifier was new in API level 13. To avoid any issues, always include a set of 787default resources (a set of resources with <em>no qualifiers</em>). For more information, see the 788section about <a href="#Compatibility">Providing the Best Device Compatibility with 789Resources</a>.</p> 790 791 792 793<h3 id="QualifierRules">Qualifier name rules</h3> 794 795<p>Here are some rules about using configuration qualifier names:</p> 796 797<ul> 798 <li>You can specify multiple qualifiers for a single set of resources, separated by dashes. For 799example, <code>drawable-en-rUS-land</code> applies to US-English devices in landscape 800orientation.</li> 801 <li>The qualifiers must be in the order listed in <a href="#table2">table 2</a>. For 802example: 803 <ul> 804 <li>Wrong: <code>drawable-hdpi-port/</code></li> 805 <li>Correct: <code>drawable-port-hdpi/</code></li> 806 </ul> 807 </li> 808 <li>Alternative resource directories cannot be nested. For example, you cannot have 809<code>res/drawable/drawable-en/</code>.</li> 810 <li>Values are case-insensitive. The resource compiler converts directory names 811 to lower case before processing to avoid problems on case-insensitive 812 file systems. Any capitalization in the names is only to benefit readability.</li> 813 <li>Only one value for each qualifier type is supported. For example, if you want to use 814the same drawable files for Spain and France, you <em>cannot</em> have a directory named 815<code>drawable-rES-rFR/</code>. Instead you need two resource directories, such as 816<code>drawable-rES/</code> and <code>drawable-rFR/</code>, which contain the appropriate files. 817However, you are not required to actually duplicate the same files in both locations. Instead, you 818can create an alias to a resource. See <a href="#AliasResources">Creating 819alias resources</a> below.</li> 820</ul> 821 822<p>After you save alternative resources into directories named with 823these qualifiers, Android automatically applies the resources in your application based on the 824current device configuration. Each time a resource is requested, Android checks for alternative 825resource directories that contain the requested resource file, then <a href="#BestMatch">finds the 826best-matching resource</a> (discussed below). If there are no alternative resources that match 827a particular device configuration, then Android uses the corresponding default resources (the 828set of resources for a particular resource type that does not include a configuration 829qualifier).</p> 830 831 832 833<h3 id="AliasResources">Creating alias resources</h3> 834 835<p>When you have a resource that you'd like to use for more than one device 836configuration (but do not want to provide as a default resource), you do not need to put the same 837resource in more than one alternative resource directory. Instead, you can (in some cases) create an 838alternative 839resource that acts as an alias for a resource saved in your default resource directory.</p> 840 841<p class="note"><strong>Note:</strong> Not all resources offer a mechanism by which you can 842create an alias to another resource. In particular, animation, menu, raw, and other unspecified 843resources in the {@code xml/} directory do not offer this feature.</p> 844 845<p>For example, imagine you have an application icon, {@code icon.png}, and need unique version of 846it for different locales. However, two locales, English-Canadian and French-Canadian, need to 847use the same version. You might assume that you need to copy the same image 848into the resource directory for both English-Canadian and French-Canadian, but it's 849not true. Instead, you can save the image that's used for both as {@code icon_ca.png} (any 850name other than {@code icon.png}) and put 851it in the default {@code res/drawable/} directory. Then create an {@code icon.xml} file in {@code 852res/drawable-en-rCA/} and {@code res/drawable-fr-rCA/} that refers to the {@code icon_ca.png} 853resource using the {@code <bitmap>} element. This allows you to store just one version of the 854PNG file and two small XML files that point to it. (An example XML file is shown below.)</p> 855 856 857<h4>Drawable</h4> 858 859<p>To create an alias to an existing drawable, use the {@code <bitmap>} element. 860For example:</p> 861 862<pre> 863<?xml version="1.0" encoding="utf-8"?> 864<bitmap xmlns:android="http://schemas.android.com/apk/res/android" 865 android:src="@drawable/icon_ca" /> 866</pre> 867 868<p>If you save this file as {@code icon.xml} (in an alternative resource directory, such as 869{@code res/drawable-en-rCA/}), it is compiled into a resource that you 870can reference as {@code R.drawable.icon}, but is actually an alias for the {@code 871R.drawable.icon_ca} resource (which is saved in {@code res/drawable/}).</p> 872 873 874<h4>Layout</h4> 875 876<p>To create an alias to an existing layout, use the {@code <include>} 877element, wrapped in a {@code <merge>}. For example:</p> 878 879<pre> 880<?xml version="1.0" encoding="utf-8"?> 881<merge> 882 <include layout="@layout/main_ltr"/> 883</merge> 884</pre> 885 886<p>If you save this file as {@code main.xml}, it is compiled into a resource you can reference 887as {@code R.layout.main}, but is actually an alias for the {@code R.layout.main_ltr} 888resource.</p> 889 890 891<h4>Strings and other simple values</h4> 892 893<p>To create an alias to an existing string, simply use the resource ID of the desired 894string as the value for the new string. For example:</p> 895 896<pre> 897<?xml version="1.0" encoding="utf-8"?> 898<resources> 899 <string name="hello">Hello</string> 900 <string name="hi">@string/hello</string> 901</resources> 902</pre> 903 904<p>The {@code R.string.hi} resource is now an alias for the {@code R.string.hello}.</p> 905 906<p> <a href="{@docRoot}guide/topics/resources/more-resources.html">Other simple values</a> work the 907same way. For example, a color:</p> 908 909<pre> 910<?xml version="1.0" encoding="utf-8"?> 911<resources> 912 <color name="yellow">#f00</color> 913 <color name="highlight">@color/red</color> 914</resources> 915</pre> 916 917 918 919 920<h2 id="Compatibility">Providing the Best Device Compatibility with Resources</h2> 921 922<p>In order for your application to support multiple device configurations, it's very important that 923you always provide default resources for each type of resource that your application uses.</p> 924 925<p>For example, if your application supports several languages, always include a {@code 926values/} directory (in which your strings are saved) <em>without</em> a <a 927href="#LocaleQualifier">language and region qualifier</a>. If you instead put all your string files 928in directories that have a language and region qualifier, then your application will crash when run 929on a device set to a language that your strings do not support. But, as long as you provide default 930{@code values/} resources, then your application will run properly (even if the user doesn't 931understand that language—it's better than crashing).</p> 932 933<p>Likewise, if you provide different layout resources based on the screen orientation, you should 934pick one orientation as your default. For example, instead of providing layout resources in {@code 935layout-land/} for landscape and {@code layout-port/} for portrait, leave one as the default, such as 936{@code layout/} for landscape and {@code layout-port/} for portrait.</p> 937 938<p>Providing default resources is important not only because your application might run on a 939configuration you had not anticipated, but also because new versions of Android sometimes add 940configuration qualifiers that older versions do not support. If you use a new resource qualifier, 941but maintain code compatibility with older versions of Android, then when an older version of 942Android runs your application, it will crash if you do not provide default resources, because it 943cannot use the resources named with the new qualifier. For example, if your <a 944href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code 945minSdkVersion}</a> is set to 4, and you qualify all of your drawable resources using <a 946href="#NightQualifier">night mode</a> ({@code night} or {@code notnight}, which were added in API 947Level 8), then an API level 4 device cannot access your drawable resources and will crash. In this 948case, you probably want {@code notnight} to be your default resources, so you should exclude that 949qualifier so your drawable resources are in either {@code drawable/} or {@code drawable-night/}.</p> 950 951<p>So, in order to provide the best device compatibility, always provide default 952resources for the resources your application needs to perform properly. Then create alternative 953resources for specific device configurations using the configuration qualifiers.</p> 954 955<p>There is one exception to this rule: If your application's <a 956href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code minSdkVersion}</a> is 4 or 957greater, you <em>do not</em> need default drawable resources when you provide alternative drawable 958resources with the <a href="#DensityQualifier">screen density</a> qualifier. Even without default 959drawable resources, Android can find the best match among the alternative screen densities and scale 960the bitmaps as necessary. However, for the best experience on all types of devices, you should 961provide alternative drawables for all three types of density. If your <a 962href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code minSdkVersion}</a> is 963<em>less than</em> 4 (Android 1.5 or lower), be aware that the screen size, density, and aspect 964qualifiers are not supported on Android 1.5 or lower, so you might need to perform additional 965compatibility for these versions.</p> 966 967 968<h3 id="ScreenCompatibility">Providing screen resource compatibility for Android 1.5</h3> 969 970<p>Android 1.5 (and lower) does not support the following configuration qualifers:</p> 971<dl> 972 <dt><a href="#DensityQualifier">Density</a></dt> 973 <dd>{@code ldpi}, {@code mdpi}, {@code ldpi}, and {@code nodpi}</dd> 974 <dt><a href="#ScreenSizeQualifier">Screen size</a></dt> 975 <dd>{@code small}, {@code normal}, and {@code large}</dd> 976 <dt><a href="#ScreenAspectQualifier">Screen aspect</a></dt> 977 <dd>{@code long} and {@code notlong}</dd> 978</dl> 979 980<p>These configuration qualifiers were introduced in Android 1.6, so Android 1.5 (API level 3) and 981lower does not support them. If you use these configuration qualifiers and do not provide 982corresponding default resources, then an Android 1.5 device might use any one of the resource 983directories named with the above screen configuration qualifiers, because it ignores these 984qualifiers and uses whichever otherwise-matching drawable resource it finds first.</p> 985 986<p>For example, if your application supports Android 1.5 and includes drawable resources for 987each density type ({@code drawable-ldpi/}, {@code drawable-mdpi/}, and {@code drawable-ldpi/}), 988and does <em>not</em> include default drawable resources ({@code drawable/}), then 989an Android 1.5 will use drawables from any one of the alternative resource directories, which 990can result in a user interface that's less than ideal.<p> 991 992<p>So, to provide compatibility with Android 1.5 (and lower) when using the screen configuration 993qualifiers:</p> 994<ol> 995 <li>Provide default resources that are for medium-density, normal, and notlong screens. 996 997 <p>Because all Android 1.5 devices have medium-density, normal, not-long screens, you can 998place these kinds of resources in the corresponding default resource directory. For example, put all 999medium density drawable resources in {@code drawable/} (instead of {@code drawable-mdpi/}), 1000put {@code normal} size resources in the corresponding default resource directory, and {@code 1001notlong} resources in the corresponding default resource directory.</p> 1002 </li> 1003 1004 <li>Ensure that your <a href="{@docRoot}tools/sdk/tools-notes.html">SDK Tools</a> version 1005is r6 or greater. 1006 1007 <p>You need SDK Tools, Revision 6 (or greater), because it includes a new packaging tool that 1008automatically applies an appropriate <a href="#VersionQualifier">version qualifier</a> to any 1009resource directory named with a qualifier that does not exist in Android 1.0. For example, because 1010the density qualifier was introduced in Android 1.6 (API level 4), when the packaging tool 1011encounters a resource directory using the density qualifier, it adds {@code v4} to the directory 1012name to ensure that older versions do not use those resources (only API level 4 and higher support 1013that qualifier). Thus, by putting your medium-density resources in a directory <em>without</em> the 1014{@code mdpi} qualifier, they are still accessible by Android 1.5, and any device that supports the 1015density qualifer and has a medium-density screen also uses the default resources (which are mdpi) 1016because they are the best match for the device (instead of using the {@code ldpi} or {@code hdpi} 1017resources).</p> 1018</li> 1019</ol> 1020 1021<p class="note"><strong>Note:</strong> Later versions of Android, such as API level 8, 1022introduce other configuration qualifiers that older version do not support. To provide the best 1023compatibility, you should always include a set of default resources for each type of resource 1024that your application uses, as discussed above to provide the best device compatibility.</p> 1025 1026 1027 1028<h2 id="BestMatch">How Android Finds the Best-matching Resource</h2> 1029 1030<p>When you request a resource for which you provide alternatives, Android selects which 1031alternative resource to use at runtime, depending on the current device configuration. To 1032demonstrate how Android selects an alternative resource, assume the following drawable directories 1033each contain different versions of the same images:</p> 1034 1035<pre class="classic no-pretty-print"> 1036drawable/ 1037drawable-en/ 1038drawable-fr-rCA/ 1039drawable-en-port/ 1040drawable-en-notouch-12key/ 1041drawable-port-ldpi/ 1042drawable-port-notouch-12key/ 1043</pre> 1044 1045<p>And assume the following is the device configuration:</p> 1046 1047<p style="margin-left:1em;"> 1048Locale = <code>en-GB</code> <br/> 1049Screen orientation = <code>port</code> <br/> 1050Screen pixel density = <code>hdpi</code> <br/> 1051Touchscreen type = <code>notouch</code> <br/> 1052Primary text input method = <code>12key</code> 1053</p> 1054 1055<p>By comparing the device configuration to the available alternative resources, Android selects 1056drawables from {@code drawable-en-port}.</p> 1057 1058<p>The system arrives at its decision for which resources to use with the following 1059logic:</p> 1060 1061 1062<div class="figure" style="width:371px"> 1063<img src="{@docRoot}images/resources/res-selection-flowchart.png" alt="" height="471" /> 1064<p class="img-caption"><strong>Figure 2.</strong> Flowchart of how Android finds the 1065best-matching resource.</p> 1066</div> 1067 1068 1069<ol> 1070 <li>Eliminate resource files that contradict the device configuration. 1071 <p>The <code>drawable-fr-rCA/</code> directory is eliminated, because it 1072contradicts the <code>en-GB</code> locale.</p> 1073<pre class="classic no-pretty-print"> 1074drawable/ 1075drawable-en/ 1076<strike>drawable-fr-rCA/</strike> 1077drawable-en-port/ 1078drawable-en-notouch-12key/ 1079drawable-port-ldpi/ 1080drawable-port-notouch-12key/ 1081</pre> 1082<p class="note"><strong>Exception:</strong> Screen pixel density is the one qualifier that is not 1083eliminated due to a contradiction. Even though the screen density of the device is hdpi, 1084<code>drawable-port-ldpi/</code> is not eliminated because every screen density is 1085considered to be a match at this point. More information is available in the <a 1086href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple 1087Screens</a> document.</p></li> 1088 1089 <li>Pick the (next) highest-precedence qualifier in the list (<a href="#table2">table 2</a>). 1090(Start with MCC, then move down.) </li> 1091 <li>Do any of the resource directories include this qualifier? </li> 1092 <ul> 1093 <li>If No, return to step 2 and look at the next qualifier. (In the example, 1094 the answer is "no" until the language qualifier is reached.)</li> 1095 <li>If Yes, continue to step 4.</li> 1096 </ul> 1097 </li> 1098 1099 <li>Eliminate resource directories that do not include this qualifier. In the example, the system 1100eliminates all the directories that do not include a language qualifier:</li> 1101<pre class="classic no-pretty-print"> 1102<strike>drawable/</strike> 1103drawable-en/ 1104drawable-en-port/ 1105drawable-en-notouch-12key/ 1106<strike>drawable-port-ldpi/</strike> 1107<strike>drawable-port-notouch-12key/</strike> 1108</pre> 1109<p class="note"><strong>Exception:</strong> If the qualifier in question is screen pixel density, 1110Android selects the option that most closely matches the device screen density. 1111In general, Android prefers scaling down a larger original image to scaling up a smaller 1112original image. See <a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple 1113Screens</a>.</p> 1114 </li> 1115 1116 <li>Go back and repeat steps 2, 3, and 4 until only one directory remains. In the example, screen 1117orientation is the next qualifier for which there are any matches. 1118So, resources that do not specify a screen orientation are eliminated: 1119<pre class="classic no-pretty-print"> 1120<strike>drawable-en/</strike> 1121drawable-en-port/ 1122<strike>drawable-en-notouch-12key/</strike> 1123</pre> 1124<p>The remaining directory is {@code drawable-en-port}.</p> 1125 </li> 1126</ol> 1127 1128<p>Though this procedure is executed for each resource requested, the system further optimizes 1129some aspects. One such optimization is that once the device configuration is known, it might 1130eliminate alternative resources that can never match. For example, if the configuration 1131language is English ("en"), then any resource directory that has a language qualifier set to 1132something other than English is never included in the pool of resources checked (though a 1133resource directory <em>without</em> the language qualifier is still included).</p> 1134 1135<p>When selecting resources based on the screen size qualifiers, the system will use resources 1136designed for a screen smaller than the current screen if there are no resources that better match 1137(for example, a large-size screen will use normal-size screen resources if necessary). However, if 1138the only available resources are <em>larger</em> than the current screen, the system will 1139<strong>not</strong> use them and your application will crash if no other resources match the device 1140configuration (for example, if all layout resources are tagged with the {@code xlarge} qualifier, 1141but the device is a normal-size screen).</p> 1142 1143<p class="note"><strong>Note:</strong> The <em>precedence</em> of the qualifier (in <a 1144href="#table2">table 2</a>) is more important 1145than the number of qualifiers that exactly match the device. For example, in step 4 above, the last 1146choice on the list includes three qualifiers that exactly match the device (orientation, touchscreen 1147type, and input method), while <code>drawable-en</code> has only one parameter that matches 1148(language). However, language has a higher precedence than these other qualifiers, so 1149<code>drawable-port-notouch-12key</code> is out.</p> 1150 1151<p>To learn more about how to use resources in your application, continue to <a 1152href="accessing-resources.html">Accessing Resources</a>.</p> 1153 1154 1155 1156 1157<h2 id="KnownIssues">Known Issues</h2> 1158 1159<h3>Android 1.5 and 1.6: Version qualifier performs exact match, instead of best match</h3> 1160 1161<p>The correct behavior is for the system to match resources marked with a <a 1162href="#VersionQualifier">version qualifier</a> equal 1163to or less than the platform version on the device, but on Android 1.5 and 1.6, (API level 3 and 4), 1164there is a bug that causes the system to match resources marked with the version qualifier 1165only when it exactly matches the version on the device.</p> 1166 1167<p><b>The workaround:</b> To provide version-specific resources, abide by this behavior. However, 1168because this bug is fixed in versions of Android available after 1.6, if 1169you need to differentiate resources between Android 1.5, 1.6, and later versions, then you only need 1170to apply the version qualifier to the 1.6 resources and one to match all later versions. Thus, this 1171is effectively a non-issue.</p> 1172 1173<p>For example, if you want drawable resources that are different on each Android 1.5, 1.6, 1174and 2.0.1 (and later), create three drawable directories: {@code drawable/} (for 1.5 and lower), 1175{@code drawable-v4} (for 1.6), and {@code drawable-v6} (for 2.0.1 and later—version 2.0, v5, 1176is no longer available).</p> 1177 1178 1179