providing-resources.jd revision ae5335b673be71fe96b8871ea376337d29e01e6e
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 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>anim/</code></td> 92 <td>XML files that define tween animations. See <a 93href="animation-resource.html">Animation Resources</a>.</td> 94 </tr> 95 96 <tr> 97 <td><code>color/</code></td> 98 <td>XML files that define a state list of colors. See <a href="color-list-resource.html">Color 99State List Resource</a></td> 100 </tr> 101 102 <tr> 103 <td><code>drawable/</code></td> 104 <td><p>Bitmap files ({@code .png}, {@code .9.png}, {@code .jpg}, {@code .gif}) or XML files that 105are compiled into the following drawable resource subtypes:</p> 106 <ul> 107 <li>Bitmap files</li> 108 <li>Nine-Patches (re-sizable bitmaps)</li> 109 <li>State lists</li> 110 <li>Shapes</li> 111 <li>Animation drawables</li> 112 <li>Other drawables</li> 113 </ul> 114 <p>See <a href="drawable-resource.html">Drawable Resources</a>.</p> 115 </td> 116 </tr> 117 118 <tr> 119 <td><code>layout/</code></td> 120 <td>XML files that define a user interface layout. 121 See <a href="layout-resource.html">Layout Resource</a>.</td> 122 </tr> 123 124 <tr> 125 <td><code>menu/</code></td> 126 <td>XML files that define application menus, such as an Options Menu, Context Menu, or Sub 127Menu. See <a href="menu-resource.html">Menu Resource</a>.</td> 128 </tr> 129 130 <tr> 131 <td><code>raw/</code></td> 132 <td><p>Arbitrary files to save in their raw form. To open these resources with a raw 133{@link java.io.InputStream}, call {@link android.content.res.Resources#openRawResource(int) 134Resources.openRawResource()} with the resource ID, which is {@code R.raw.<em>filename</em>}.</p> 135 <p>However, if you need access to original file names and file hierarchy, you might consider 136saving some resources in the {@code 137assets/} directory (instead of {@code res/raw/}). Files in {@code assets/} are not given a 138resource ID, so you can read them only using {@link android.content.res.AssetManager}.</p></td> 139 </tr> 140 141 <tr> 142 <td><code>values/</code></td> 143 <td><p>XML files that contain simple values, such as strings, integers, and colors.</p> 144 <p>Whereas XML resource files in other {@code res/} subdirectories define a single resource 145based on the XML filename, files in the {@code values/} directory describe multiple resources. 146For a file in this directory, each child of the {@code <resources>} element defines a single 147resource. For example, a {@code <string>} element creates an 148{@code R.string} resource and a {@code <color>} element creates an {@code R.color} 149resource.</p> 150 <p>Because each resource is defined with its own XML element, you can name the file 151whatever you want and place different resource types in one file. However, for clarity, you might 152want to place unique resource types in different files. For example, here are some filename 153conventions for resources you can create in this directory:</p> 154 <ul> 155 <li>arrays.xml for resource arrays (<a 156href="more-resources.html#TypedArray">typed arrays</a>).</li> 157 <li>colors.xml for <a 158href="more-resources.html#Color">color values</a></li> 159 <li>dimens.xml for <a 160href="more-resources.html#Dimension">dimension values</a>.</li> 161 <li>strings.xml for <a href="string-resource.html">string 162values</a>.</li> 163 <li>styles.xml for <a href="style-resource.html">styles</a>.</li> 164 </ul> 165 <p>See <a href="string-resource.html">String Resources</a>, 166 <a href="style-resource.html">Style Resource</a>, and 167 <a href="more-resources.html">More Resource Types</a>.</p> 168 </td> 169 </tr> 170 171 <tr> 172 <td><code>xml/</code></td> 173 <td>Arbitrary XML files that can be read at runtime by calling {@link 174android.content.res.Resources#getXml(int) Resources.getXML()}. Various XML configuration files 175must be saved here, such as a <a 176href="{@docRoot}guide/topics/search/searchable-config.html">searchable configuration</a>. 177<!-- or preferences configuration. --></td> 178 </tr> 179</table> 180 181<p class="caution"><strong>Caution:</strong> Never save resource files directly inside the 182{@code res/} directory—it will cause a compiler error.</p> 183 184<p>For more information about certain types of resources, see the <a 185href="available-resources.html">Resource Types</a> documentation.</p> 186 187<p>The resources that you save in the subdirectories defined in table 1 are your "default" 188resources. That is, these resources define the default design and content for your application. 189However, different types of Android-powered devices might call for different types of resources. 190For example, if a device has a larger than normal screen, then you should provide 191different layout resources that take advantage of the extra screen space. Or, if a device has a 192different language setting, then you should provide different string resources that translate the 193text in your user interface. To provide these different resources for different device 194configurations, you need to provide alternative resources, in addition to your default 195resources.</p> 196 197 198<h2 id="AlternativeResources">Providing Alternative Resources</h2> 199 200 201<div class="figure" style="width:421px"> 202<img src="{@docRoot}images/resources/resource_devices_diagram2.png" height="137" alt="" /> 203<p class="img-caption"> 204<strong>Figure 1.</strong> Two different devices, one using alternative resources.</p> 205</div> 206 207<p>Almost every application should provide alternative resources to support specific device 208configurations. For instance, you should include alternative drawable resources for different 209screen densities and alternative string resources for different languages. At runtime, Android 210detects the current device configuration and loads the appropriate 211resources for your application.</p> 212 213<p>To specify configuration-specific alternatives for a set of resources:</p> 214<ol> 215 <li>Create a new directory in {@code res/} named in the form {@code 216<em><resources_name></em>-<em><config_qualifier></em>}. 217 <ul> 218 <li><em>{@code <resources_name>}</em> is the directory name of the corresponding default 219resources (defined in table 1).</li> 220 <li><em>{@code <qualifier>}</em> is a name that specifies an individual configuration 221for which these resources are to be used (defined in table 2).</li> 222 </ul> 223 <p>You can append more than one <em>{@code <qualifier>}</em>. Separate each 224one with a dash.</p> 225 </li> 226 <li>Save the respective alternative resources in this new directory. The resource files must be 227named exactly the same as the default resource files.</li> 228</ol> 229 230<p>For example, here are some default and alternative resources:</p> 231 232<pre class="classic no-pretty-print"> 233res/ 234 drawable/ <span style="color:black"> 235 icon.png 236 background.png </span> 237 drawable-hdpi/ <span style="color:black"> 238 icon.png 239 background.png </span> 240</pre> 241 242<p>The {@code hdpi} qualifier indicates that the resources in that directory are for devices with a 243high-density screen. The images in each of these drawable directories are sized for a specific 244screen density, but the filenames are exactly 245the same. This way, the resource ID that you use to reference the {@code icon.png} or {@code 246background.png} image is always the same, but Android selects the 247version of each resource that best matches the current device, by comparing the device 248configuration information with the qualifiers in the alternative resource directory name.</p> 249 250<p>Android supports several configuration qualifiers and you can 251add multiple qualifiers to one directory name, by separating each qualifier with a dash. Table 2 252lists the valid configuration qualifiers, in order of precedence—if you use multiple 253qualifiers for one resource directory, they must be added to the directory name in the order they 254are listed in the table.</p> 255 256<p class="note"><strong>Note:</strong> Some configuration qualifiers were added after Android 1.0, 257so not 258all versions of Android support all the qualifiers listed in table 2. New qualifiers 259indicate the version in which they were added. To avoid any issues, always include a set of default 260resources for resources that your application uses. For more information, see the section about <a 261href="#Compatibility">Providing the Best Device Compatibility with Resources</a>.</p> 262 263<p class="table-caption" id="table2"><strong>Table 2.</strong> Configuration qualifier 264names.</p> 265<table> 266 <tr> 267 <th>Qualifier</th> 268 <th>Values</th> 269 <th>Description</th> 270 </tr> 271 <tr id="MccQualifier"> 272 <td>MCC and MNC</td> 273 <td>Examples:<br/> 274 <code>mcc310</code><br/> 275 <code><nobr>mcc310-mnc004</nobr></code><br/> 276 <code>mcc208-mnc00</code><br/> 277 etc. 278 </td> 279 <td> 280 <p>The mobile country code (MCC), optionally followed by mobile network code (MNC) 281 from the SIM card in the device. For example, <code>mcc310</code> is U.S. on any carrier, 282 <code>mcc310-mnc004</code> is U.S. on Verizon, and <code>mcc208-mnc00</code> is France on 283 Orange.</p> 284 <p>If the device uses a radio connection (GSM phone), the MCC comes 285 from the SIM, and the MNC comes from the network to which the 286 device is connected.</p> 287 <p>You can also use the MCC alone (for example, to include country-specific legal 288resources in your application). If you need to specify based on the language only, then use the 289<em>language and region</em> qualifier instead (discussed next). If you decide to use the MCC and 290MNC qualifier, you should do so with care and test that it works as expected.</p> 291 <p>Also see the configuration fields {@link 292android.content.res.Configuration#mcc}, and {@link 293android.content.res.Configuration#mnc}, which indicate the current mobile country code 294and mobile network code, respectively.</p> 295 </td> 296 </tr> 297 <tr id="LocaleQualifier"> 298 <td>Language and region</td> 299 <td>Examples:<br/> 300 <code>en</code><br/> 301 <code>fr</code><br/> 302 <code>en-rUS</code><br/> 303 <code>fr-rFR</code><br/> 304 <code>fr-rCA</code><br/> 305 etc. 306 </td> 307 <td><p>The language is defined by a two-letter <a 308href="http://www.loc.gov/standards/iso639-2/php/code_list.php">ISO 309 639-1</a> language code, optionally followed by a two letter 310 <a 311href="http://www.iso.org/iso/en/prods-services/iso3166ma/02iso-3166-code-lists/list-en1.html">ISO 312 3166-1-alpha-2</a> region code (preceded by lowercase "{@code r}"). 313 </p><p> 314 The codes are <em>not</em> case-sensitive; the {@code r} prefix is used to 315 distinguish the region portion. 316 You cannot specify a region alone.</p> 317 <p>This can change during the life 318of your application if the user changes his or her language in the system settings. See <a 319href="runtime-changes.html">Handling Runtime Changes</a> for information about 320how this can affect your application during runtime.</p> 321 <p>See <a href="localization.html">Localization</a> for a complete guide to localizing 322your application for other languages.</p> 323 <p>Also see the {@link android.content.res.Configuration#locale} configuration field, which 324indicates the current locale.</p> 325 </td> 326 </tr> 327 <tr id="ScreenSizeQualifier"> 328 <td>Screen size</td> 329 <td> 330 <code>small</code><br/> 331 <code>normal</code><br/> 332 <code>large</code><br/> 333 <code>xlarge</code> 334 </td> 335 <td> 336 <ul class="nolist"> 337 <li>{@code small}: Screens based on the space available on a 338 low-density QVGA screen. Considering a portrait HVGA display, this has 339 the same available width but less height—it is 3:4 vs. HVGA's 340 2:3 aspect ratio. Examples are QVGA low density and VGA high 341 density.</li> 342 <li>{@code normal}: Screens based on the traditional 343 medium-density HVGA screen. A screen is considered to be normal if it is 344 at least this size (independent of density) and not larger. Examples 345 of such screens a WQVGA low density, HVGA medium density, WVGA 346 high density.</li> 347 <li>{@code large}: Screens based on the space available on a 348 medium-density VGA screen. Such a screen has significantly more 349 available space in both width and height than an HVGA display. 350 Examples are VGA and WVGA medium density screens.</li> 351 <li>{@code xlarge}: Screens that are considerably larger than the traditional 352 medium-density HVGA screen. In most cases, devices with extra large screens would be too 353large to carry in a pocket and would most likely be tablet-style devices. <em>Added in API Level 3549.</em></li> 355 </ul> 356 <p><em>Added in API Level 4.</em></p> 357 <p>See <a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple 358Screens</a> for more information.</p> 359 <p>Also see the {@link android.content.res.Configuration#screenLayout} configuration field, 360which indicates whether the screen is small, normal, 361or large.</p> 362 </td> 363 </tr> 364 <tr id="ScreenAspectQualifier"> 365 <td>Screen aspect</td> 366 <td> 367 <code>long</code><br/> 368 <code>notlong</code> 369 </td> 370 <td> 371 <ul class="nolist"> 372 <li>{@code long}: Long screens, such as WQVGA, WVGA, FWVGA</li> 373 <li>{@code notlong}: Not long screens, such as QVGA, HVGA, and VGA</li> 374 </ul> 375 <p><em>Added in API Level 4.</em></p> 376 <p>This is based purely on the aspect ratio of the screen (a "long" screen is wider). This 377is not related to the screen orientation.</p> 378 <p>Also see the {@link android.content.res.Configuration#screenLayout} configuration field, 379which indicates whether the screen is long.</p> 380 </td> 381 </tr> 382 <tr id="OrientationQualifier"> 383 <td>Screen orientation</td> 384 <td> 385 <code>port</code><br/> 386 <code>land</code> <!-- <br/> 387 <code>square</code> --> 388 </td> 389 <td> 390 <ul class="nolist"> 391 <li>{@code port}: Device is in portrait orientation (vertical)</li> 392 <li>{@code land}: Device is in landscape orientation (horizontal)</li> 393 <!-- Square mode is currently not used. --> 394 </ul> 395 <p>This can change during the life of your application if the user rotates the 396screen. See <a href="runtime-changes.html">Handling Runtime Changes</a> for information about 397how this affects your application during runtime.</p> 398 <p>Also see the {@link android.content.res.Configuration#orientation} configuration field, 399which indicates the current device orientation.</p> 400 </td> 401 </tr> 402 <tr id="DockQualifier"> 403 <td>Dock mode</td> 404 <td> 405 <code>car</code><br/> 406 <code>desk</code> 407 </td> 408 <td> 409 <ul class="nolist"> 410 <li>{@code car}: Device is in a car dock</li> 411 <li>{@code desk}: Device is in a desk dock</li> 412 </ul> 413 <p><em>Added in API Level 8.</em></p> 414 <p>This can change during the life of your application if the user places the device in a 415dock. You can enable or disable this mode using {@link 416android.app.UiModeManager}. See <a href="runtime-changes.html">Handling Runtime Changes</a> for 417information about how this affects your application during runtime.</p> 418 </td> 419 </tr> 420 <tr id="NightQualifier"> 421 <td>Night mode</td> 422 <td> 423 <code>night</code><br/> 424 <code>notnight</code> 425 </td> 426 <td> 427 <ul class="nolist"> 428 <li>{@code night}: Night time</li> 429 <li>{@code notnight}: Day time</li> 430 </ul> 431 <p><em>Added in API Level 8.</em></p> 432 <p>This can change during the life of your application if night mode is left in 433auto mode (default), in which case the mode changes based on the time of day. You can enable 434or disable this mode using {@link android.app.UiModeManager}. See <a 435href="runtime-changes.html">Handling Runtime Changes</a> for information about how this affects your 436application during runtime.</p> 437 </td> 438 </tr> 439 <tr id="DensityQualifier"> 440 <td>Screen pixel density (dpi)</td> 441 <td> 442 <code>ldpi</code><br/> 443 <code>mdpi</code><br/> 444 <code>hdpi</code><br/> 445 <code>xhdpi</code><br/> 446 <code>nodpi</code> 447 </td> 448 <td> 449 <ul class="nolist"> 450 <li>{@code ldpi}: Low-density screens; approximately 120dpi.</li> 451 <li>{@code mdpi}: Medium-density (on traditional HVGA) screens; approximately 452160dpi.</li> 453 <li>{@code hdpi}: High-density screens; approximately 240dpi.</li> 454 <li>{@code xhdpi}: Extra high-density screens; approximately 320dpi. <em>Added in API 455Level 8</em></li> 456 <li>{@code nodpi}: This can be used for bitmap resources that you do not want to be scaled 457to match the device density.</li> 458 </ul> 459 <p><em>Added in API Level 4.</em></p> 460 <p>There is thus a 3:4:6 scaling ratio between the three densities, so a 9x9 bitmap 461 in ldpi is 12x12 in mdpi and 18x18 in hdpi.</p> 462 <p>When Android selects which resource files to use, 463 it handles screen density differently than the other qualifiers. 464 In step 1 of <a href="#BestMatch">How Android finds the best 465 matching directory</a> (below), screen density is always considered to 466 be a match. In step 4, if the qualifier being considered is screen 467 density, Android selects the best final match at that point, 468 without any need to move on to step 5. 469 </p> 470 <p>See <a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple 471Screens</a> for more information about how to handle screen sizes and how Android might scale 472your bitmaps.</p> 473 </td> 474 </tr> 475 <tr id="TouchscreenQualifier"> 476 <td>Touchscreen type</td> 477 <td> 478 <code>notouch</code><br/> 479 <code>stylus</code><br/> 480 <code>finger</code> 481 </td> 482 <td> 483 <ul class="nolist"> 484 <li>{@code notouch}: Device does not have a touchscreen.</li> 485 <li>{@code stylus}: Device has a resistive touchscreen that's suited for use with a 486stylus.</li> 487 <li>{@code finger}: Device has a touchscreen.</li> 488 </ul> 489 <p>Also see the {@link android.content.res.Configuration#touchscreen} configuration field, 490which indicates the type of touchscreen on the device.</p> 491 </td> 492 </tr> 493 <tr id="KeyboardAvailQualifier"> 494 <td>Keyboard availability</td> 495 <td> 496 <code>keysexposed</code><br/> 497 <code>keyssoft</code> 498 </td> 499 <td> 500 <ul class="nolist"> 501 <li>{@code keysexposed}: Device has a keyboard available. If the device has a 502software keyboard enabled (which is likely), this may be used even when the hardware keyboard is 503<em>not</em> exposed to the user, even if the device has no hardware keyboard. If no software 504keyboard is provided or it's disabled, then this is only used when a hardware keyboard is 505exposed.</li> 506 <li>{@code keyshidden}: Device has a hardware keyboard available but it is 507hidden <em>and</em> the device does <em>not</em> have a software keyboard enabled.</li> 508 <li>{@code keyssoft}: Device has a software keyboard enabled, whether it's 509visible or not.</li> 510 </ul> 511 <p>If you provide <code>keysexposed</code> resources, but not <code>keyssoft</code> 512resources, the system uses the <code>keysexposed</code> resources regardless of whether a 513keyboard is visible, as long as the system has a software keyboard enabled.</p> 514 <p>This can change during the life of your application if the user opens a hardware 515keyboard. See <a href="runtime-changes.html">Handling Runtime Changes</a> for information about how 516this affects your application during runtime.</p> 517 <p>Also see the configuration fields {@link 518android.content.res.Configuration#hardKeyboardHidden} and {@link 519android.content.res.Configuration#keyboardHidden}, which indicate the visibility of a hardware 520keyboard and and the visibility of any kind of keyboard (including software), respectively.</p> 521 </td> 522 </tr> 523 <tr id="ImeQualifier"> 524 <td>Primary text input method</td> 525 <td> 526 <code>nokeys</code><br/> 527 <code>qwerty</code><br/> 528 <code>12key</code> 529 </td> 530 <td> 531 <ul class="nolist"> 532 <li>{@code nokeys}: Device has no hardware keys for text input.</li> 533 <li>{@code qwerty}: Device has a hardware qwerty keyboard, whether it's visible to the 534user 535or not.</li> 536 <li>{@code 12key}: Device has a hardware 12-key keyboard, whether it's visible to the user 537or not.</li> 538 </ul> 539 <p>Also see the {@link android.content.res.Configuration#keyboard} configuration field, 540which indicates the primary text input method available.</p> 541 </td> 542 </tr> 543 <tr id="NavAvailQualifier"> 544 <td>Navigation key availability</td> 545 <td> 546 <code>navexposed</code><br/> 547 <code>navhidden</code> 548 </td> 549 <td> 550 <ul class="nolist"> 551 <li>{@code navexposed}: Navigation keys are available to the user.</li> 552 <li>{@code navhidden}: Navigation keys are not available (such as behind a closed 553lid).</li> 554 </ul> 555 <p>This can change during the life of your application if the user reveals the navigation 556keys. See <a href="runtime-changes.html">Handling Runtime Changes</a> for 557information about how this affects your application during runtime.</p> 558 <p>Also see the {@link android.content.res.Configuration#navigationHidden} configuration 559field, which indicates whether navigation keys are hidden.</p> 560 </td> 561 </tr> 562 <tr id="TouchQualifier"> 563 <td>Primary non-touch navigation method</td> 564 <td> 565 <code>nonav</code><br/> 566 <code>dpad</code><br/> 567 <code>trackball</code><br/> 568 <code>wheel</code> 569 </td> 570 <td> 571 <ul class="nolist"> 572 <li>{@code nonav}: Device has no navigation facility other than using the 573touchscreen.</li> 574 <li>{@code dpad}: Device has a directional-pad (d-pad) for navigation.</li> 575 <li>{@code trackball}: Device has a trackball for navigation.</li> 576 <li>{@code wheel}: Device has a directional wheel(s) for navigation (uncommon).</li> 577 </ul> 578 <p>Also see the {@link android.content.res.Configuration#navigation} configuration field, 579which indicates the type of navigation method available.</p> 580 </td> 581 </tr> 582<!-- DEPRECATED 583 <tr> 584 <td>Screen dimensions</td> 585 <td>Examples:<br/> 586 <code>320x240</code><br/> 587 <code>640x480</code><br/> 588 etc. 589 </td> 590 <td> 591 <p>The larger dimension must be specified first. <strong>This configuration is deprecated 592and should not be used</strong>. Instead use "screen size," "wider/taller screens," and "screen 593orientation" described above.</p> 594 </td> 595 </tr> 596--> 597 <tr id="VersionQualifier"> 598 <td>System Version (API Level)</td> 599 <td>Examples:<br/> 600 <code>v3</code><br/> 601 <code>v4</code><br/> 602 <code>v7</code><br/> 603 etc.</td> 604 <td> 605 <p>The API Level supported by the device. For example, <code>v1</code> for API Level 6061 (devices with Android 1.0 or higher) and <code>v4</code> for API Level 4 (devices with Android 6071.6 or higher). See the <a 608href="{@docRoot}guide/appendix/api-levels.html">Android API Levels</a> document for more information 609about these values.</p> 610 <p class="caution"><strong>Caution:</strong> Android 1.5 and 1.6 only match resources 611with this qualifier when it exactly matches the system version. See the section below about <a 612href="#KnownIssues">Known Issues</a> for more information.</p> 613 </td> 614 </tr> 615</table> 616 617 618<h3 id="QualifierRules">Qualifier name rules</h3> 619 620<p>Here are some rules about using configuration qualifier names:</p> 621 622<ul> 623 <li>You can specify multiple qualifiers for a single set of resources, separated by dashes. For 624example, <code>drawable-en-rUS-land</code> applies to US-English devices in landscape 625orientation.</li> 626 <li>The qualifiers must be in the order listed in <a href="#table2">table 2</a>. For 627example: 628 <ul> 629 <li>Wrong: <code>drawable-hdpi-port/</code></li> 630 <li>Correct: <code>drawable-port-hdpi/</code></li> 631 </ul> 632 </li> 633 <li>Alternative resource directories cannot be nested. For example, you cannot have 634<code>res/drawable/drawable-en/</code>.</li> 635 <li>Values are case-insensitive. The resource compiler converts directory names 636 to lower case before processing to avoid problems on case-insensitive 637 file systems. Any capitalization in the names is only to benefit readability.</li> 638 <li>Only one value for each qualifier type is supported. For example, if you want to use 639the same drawable files for Spain and France, you <em>cannot</em> have a directory named 640<code>drawable-rES-rFR/</code>. Instead you need two resource directories, such as 641<code>drawable-rES/</code> and <code>drawable-rFR/</code>, which contain the appropriate files. 642However, you are not required to actually duplicate the same files in both locations. Instead, you 643can create an alias to a resource. See <a href="#AliasResources">Creating 644alias resources</a> below.</li> 645</ul> 646 647<p>After you save alternative resources into directories named with 648these qualifiers, Android automatically applies the resources in your application based on the 649current device configuration. Each time a resource is requested, Android checks for alternative 650resource directories that contain the requested resource file, then <a href="#BestMatch">finds the 651best-matching resource</a> (discussed below). If there are no alternative resources that match 652a particular device configuration, then Android uses the corresponding default resources (the 653set of resources for a particular resource type that does not include a configuration 654qualifier).</p> 655 656 657 658<h3 id="AliasResources">Creating alias resources</h3> 659 660<p>When you have a resource that you'd like to use for more than one device 661configuration (but do not want to provide as a default resource), you do not need to put the same 662resource in more than one alternative resource directory. Instead, you can (in some cases) create an 663alternative 664resource that acts as an alias for a resource saved in your default resource directory.</p> 665 666<p class="note"><strong>Note:</strong> Not all resources offer a mechanism by which you can 667create an alias to another resource. In particular, animation, menu, raw, and other unspecified 668resources in the {@code xml/} directory do not offer this feature.</p> 669 670<p>For example, imagine you have an application icon, {@code icon.png}, and need unique version of 671it for different locales. However, two locales, English-Canadian and French-Canadian, need to 672use the same version. You might assume that you need to copy the same image 673into the resource directory for both English-Canadian and French-Canadian, but it's 674not true. Instead, you can save the image that's used for both as {@code icon_ca.png} (any 675name other than {@code icon.png}) and put 676it in the default {@code res/drawable/} directory. Then create an {@code icon.xml} file in {@code 677res/drawable-en-rCA/} and {@code res/drawable-fr-rCA/} that refers to the {@code icon_ca.png} 678resource using the {@code <bitmap>} element. This allows you to store just one version of the 679PNG file and two small XML files that point to it. (An example XML file is shown below.)</p> 680 681 682<h4>Drawable</h4> 683 684<p>To create an alias to an existing drawable, use the {@code <bitmap>} element. 685For example:</p> 686 687<pre> 688<?xml version="1.0" encoding="utf-8"?> 689<bitmap xmlns:android="http://schemas.android.com/apk/res/android" 690 android:src="@drawable/icon_ca" /> 691</pre> 692 693<p>If you save this file as {@code icon.xml} (in an alternative resource directory, such as 694{@code res/drawable-en-rCA/}), it is compiled into a resource that you 695can reference as {@code R.drawable.icon}, but is actually an alias for the {@code 696R.drawable.icon_ca} resource (which is saved in {@code res/drawable/}).</p> 697 698 699<h4>Layout</h4> 700 701<p>To create an alias to an existing layout, use the {@code <include>} 702element, wrapped in a {@code <merge>}. For example:</p> 703 704<pre> 705<?xml version="1.0" encoding="utf-8"?> 706<merge> 707 <include layout="@layout/main_ltr"/> 708</merge> 709</pre> 710 711<p>If you save this file as {@code main.xml}, it is compiled into a resource you can reference 712as {@code R.layout.main}, but is actually an alias for the {@code R.layout.main_ltr} 713resource.</p> 714 715 716<h4>Strings and other simple values</h4> 717 718<p>To create an alias to an existing string, simply use the resource ID of the desired 719string as the value for the new string. For example:</p> 720 721<pre> 722<?xml version="1.0" encoding="utf-8"?> 723<resources> 724 <string name="hello">Hello</string> 725 <string name="hi">@string/hello</string> 726</resources> 727</pre> 728 729<p>The {@code R.string.hi} resource is now an alias for the {@code R.string.hello}.</p> 730 731<p> <a href="{@docRoot}guide/topics/resources/more-resources.html">Other simple values</a> work the 732same way. For example, a color:</p> 733 734<pre> 735<?xml version="1.0" encoding="utf-8"?> 736<resources> 737 <color name="yellow">#f00</color> 738 <color name="highlight">@color/red</color> 739</resources> 740</pre> 741 742 743 744 745<h2 id="Compatibility">Providing the Best Device Compatibility with Resources</h2> 746 747<p>In order for your application to support multiple device configurations, it's very important that 748you always provide default resources for each type of resource that your application uses.</p> 749 750<p>For example, if your application supports several languages, always include a {@code 751values/} directory (in which your strings are saved) <em>without</em> a <a 752href="#LocalQualifier">language and region qualifier</a>. If you instead put all your string files 753in directories that have a language and region qualifier, then your application will crash when run 754on a device set to a language that your strings do not support. But, as long as you provide default 755{@code values/} resources, then your application will run properly (even if the user doesn't 756understand that language—it's better than crashing).</p> 757 758<p>Likewise, if you provide different layout resources based on the screen orientation, you should 759pick one orientation as your default. For example, instead of providing layout resources in {@code 760layout-land/} for landscape and {@code layout-port/} for portrait, leave one as the default, such as 761{@code layout/} for landscape and {@code layout-port/} for portrait.</p> 762 763<p>Providing default resources is important not only because your application might run on a 764configuration you had not anticipated, but also because new versions of Android sometimes add 765configuration qualifiers that older versions do not support. If you use a new resource qualifier, 766but maintain code compatibility with older versions of Android, then when an older version of 767Android runs your application, it will crash if you do not provide default resources, because it 768cannot use the resources named with the new qualifier. For example, if your <a 769href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code 770minSdkVersion}</a> is set to 4, and you qualify all of your drawable resources using <a 771href="#NightQualifier">night mode</a> ({@code night} or {@code notnight}, which were added in API 772Level 8), then an API Level 4 device cannot access your drawable resources and will crash. In this 773case, you probably want {@code notnight} to be your default resources, so you should exclude that 774qualifier so your drawable resources are in either {@code drawable/} or {@code drawable-night/}.</p> 775 776<p>So, in order to provide the best device compatibility, always provide default 777resources for the resources your application needs to perform properly. Then create alternative 778resources for specific device configurations using the configuration qualifiers.</p> 779 780<p>There is one exception to this rule: If your application's <a 781href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code minSdkVersion}</a> is 4 or 782greater, you <em>do not</em> need default drawable resources when you provide alternative drawable 783resources with the <a href="#DensityQualifier">screen density</a> qualifier. Even without default 784drawable resources, Android can find the best match among the alternative screen densities and scale 785the bitmaps as necessary. However, for the best experience on all types of devices, you should 786provide alternative drawables for all three types of density. If your <a 787href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code minSdkVersion}</a> is 788<em>less than</em> 4 (Android 1.5 or lower), be aware that the screen size, density, and aspect 789qualifiers are not supported on Android 1.5 or lower, so you might need to perform additional 790compatibility for these versions.</p> 791 792 793<h3 id="ScreenCompatibility">Providing screen resource compatibility for Android 1.5</h3> 794 795<p>Android 1.5 (and lower) does not support the following configuration qualifers:</p> 796<dl> 797 <dt><a href="#DensityQualifier">Density</a></dt> 798 <dd>{@code ldpi}, {@code mdpi}, {@code ldpi}, and {@code nodpi}</dd> 799 <dt><a href="#ScreenSizeQualifier">Screen size</a></dt> 800 <dd>{@code small}, {@code normal}, and {@code large}</dd> 801 <dt><a href="#ScreenAspectQualifier">Screen aspect</a></dt> 802 <dd>{@code long} and {@code notlong}</dd> 803</dl> 804 805<p>These configuration qualifiers were introduced in Android 1.6, so Android 1.5 (API Level 3) and 806lower does not support them. If you use these configuration qualifiers and do not provide 807corresponding default resources, then an Android 1.5 device might use any one of the resource 808directories named with the above screen configuration qualifiers, because it ignores these 809qualifiers and uses whichever otherwise-matching drawable resource it finds first.</p> 810 811<p>For example, if your application supports Android 1.5 and includes drawable resources for 812each density type ({@code drawable-ldpi/}, {@code drawable-mdpi/}, and {@code drawable-ldpi/}), 813and does <em>not</em> include default drawable resources ({@code drawable/}), then 814an Android 1.5 will use drawables from any one of the alternative resource directories, which 815can result in a user interface that's less than ideal.<p> 816 817<p>So, to provide compatibility with Android 1.5 (and lower) when using the screen configuration 818qualifiers:</p> 819<ol> 820 <li>Provide default resources that are for medium-density, normal, and notlong screens. 821 822 <p>Because all Android 1.5 devices have medium-density, normal, not-long screens, you can 823place these kinds of resources in the corresponding default resource directory. For example, put all 824medium density drawable resources in {@code drawable/} (instead of {@code drawable-mdpi/}), 825put {@code normal} size resources in the corresponding default resource directory, and {@code 826notlong} resources in the corresponding default resource directory.</p> 827 </li> 828 829 <li>Ensure that your <a href="{@docRoot}sdk/tools-notes.html">SDK Tools</a> version 830is r6 or greater. 831 832 <p>You need SDK Tools, Revision 6 (or greater), because it includes a new packaging tool that 833automatically applies an appropriate <a href="#VersionQualifier">version qualifier</a> to any 834resource directory named with a qualifier that does not exist in Android 1.0. For example, because 835the density qualifier was introduced in Android 1.6 (API Level 4), when the packaging tool 836encounters a resource directory using the density qualifier, it adds {@code v4} to the directory 837name to ensure that older versions do not use those resources (only API Level 4 and higher support 838that qualifier). Thus, by putting your medium-density resources in a directory <em>without</em> the 839{@code mdpi} qualifier, they are still accessible by Android 1.5, and any device that supports the 840density qualifer and has a medium-density screen also uses the default resources (which are mdpi) 841because they are the best match for the device (instead of using the {@code ldpi} or {@code hdpi} 842resources).</p> 843</li> 844</ol> 845 846<p class="note"><strong>Note:</strong> Later versions of Android, such as API Level 8, 847introduce other configuration qualifiers that older version do not support. To provide the best 848compatibility, you should always include a set of default resources for each type of resource 849that your application uses, as discussed above to provide the best device compatibility.</p> 850 851 852 853<h2 id="BestMatch">How Android Finds the Best-matching Resource</h2> 854 855<p>When you request a resource for which you provide alternatives, Android selects which 856alternative resource to use at runtime, depending on the current device configuration. To 857demonstrate how Android selects an alternative resource, assume the following drawable directories 858each contain different versions of the same images:</p> 859 860<pre class="classic no-pretty-print"> 861drawable/ 862drawable-en/ 863drawable-fr-rCA/ 864drawable-en-port/ 865drawable-en-notouch-12key/ 866drawable-port-ldpi/ 867drawable-port-notouch-12key/ 868</pre> 869 870<p>And assume the following is the device configuration:</p> 871 872<p style="margin-left:1em;"> 873Locale = <code>en-GB</code> <br/> 874Screen orientation = <code>port</code> <br/> 875Screen pixel density = <code>hdpi</code> <br/> 876Touchscreen type = <code>notouch</code> <br/> 877Primary text input method = <code>12key</code> 878</p> 879 880<p>By comparing the device configuration to the available alternative resources, Android selects 881drawables from {@code drawable-en-port}. It arrives at this decision using the following logic:</p> 882 883 884<div class="figure" style="width:280px"> 885<img src="{@docRoot}images/resources/res-selection-flowchart.png" alt="" height="590" /> 886<p class="img-caption"><strong>Figure 2.</strong> Flowchart of how Android finds the 887best-matching resource.</p> 888</div> 889 890 891<ol> 892 <li>Eliminate resource files that contradict the device configuration. 893 <p>The <code>drawable-fr-rCA/</code> directory is eliminated, because it 894contradicts the <code>en-GB</code> locale.</p> 895<pre class="classic no-pretty-print"> 896drawable/ 897drawable-en/ 898<strike>drawable-fr-rCA/</strike> 899drawable-en-port/ 900drawable-en-notouch-12key/ 901drawable-port-ldpi/ 902drawable-port-notouch-12key/ 903</pre> 904<p class="note"><strong>Exception:</strong> Screen pixel density is the one qualifier that is not 905eliminated due to a contradiction. Even though the screen density of the device is hdpi, 906<code>drawable-port-ldpi/</code> is not eliminated because every screen density is 907considered to be a match at this point. More information is available in the <a 908href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple 909Screens</a> document.</p></li> 910 911 <li>Pick the (next) highest-precedence qualifier in the list (<a href="#table2">table 2</a>). 912(Start with MCC, then move down.) </li> 913 <li>Do any of the resource directories include this qualifier? </li> 914 <ul> 915 <li>If No, return to step 2 and look at the next qualifier. (In the example, 916 the answer is "no" until the language qualifier is reached.)</li> 917 <li>If Yes, continue to step 4.</li> 918 </ul> 919 </li> 920 921 <li>Eliminate resource directories that do not include this qualifier. In the example, the system 922eliminates all the directories that do not include a language qualifier:</li> 923<pre class="classic no-pretty-print"> 924<strike>drawable/</strike> 925drawable-en/ 926drawable-en-port/ 927drawable-en-notouch-12key/ 928<strike>drawable-port-ldpi/</strike> 929<strike>drawable-port-notouch-12key/</strike> 930</pre> 931<p class="note"><strong>Exception:</strong> If the qualifier in question is screen pixel density, 932Android selects the option that most closely matches the device screen density. 933In general, Android prefers scaling down a larger original image to scaling up a smaller 934original image. See <a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple 935Screens</a>.</p> 936 </li> 937 938 <li>Go back and repeat steps 2, 3, and 4 until only one directory remains. In the example, screen 939orientation is the next qualifier for which there are any matches. 940So, resources that do not specify a screen orientation are eliminated: 941<pre class="classic no-pretty-print"> 942<strike>drawable-en/</strike> 943drawable-en-port/ 944<strike>drawable-en-notouch-12key/</strike> 945</pre> 946<p>The remaining directory is {@code drawable-en-port}.</p> 947 </li> 948</ol> 949 950<p>Though this procedure is executed for each resource requested, the system further optimizes 951some aspects. One such optimization is that once the device configuration is known, it might 952eliminate alternative resources that can never match. For example, if the configuration 953language is English ("en"), then any resource directory that has a language qualifier set to 954something other than English is never included in the pool of resources checked (though a 955resource directory <em>without</em> the language qualifier is still included).</p> 956 957<p class="note"><strong>Note:</strong> The <em>precedence</em> of the qualifier (in <a 958href="#table2">table 2</a>) is more important 959than the number of qualifiers that exactly match the device. For example, in step 4 above, the last 960choice on the list includes three qualifiers that exactly match the device (orientation, touchscreen 961type, and input method), while <code>drawable-en</code> has only one parameter that matches 962(language). However, language has a higher precedence than these other qualifiers, so 963<code>drawable-port-notouch-12key</code> is out.</p> 964 965<p>To learn more about how to use resources in your application, continue to <a 966href="accessing-resources.html">Accessing Resources</a>.</p> 967 968 969 970 971<h2 id="KnownIssues">Known Issues</h2> 972 973<h3>Android 1.5 and 1.6: Version qualifier performs exact match, instead of best match</h3> 974 975<p>The correct behavior is for the system to match resources marked with a <a 976href="#VersionQualifier">version qualifier</a> equal 977to or less than the system version on the device, but on Android 1.5 and 1.6, (API Level 3 and 4), 978there is a bug that causes the system to match resources marked with the version qualifier 979only when it exactly matches the version on the device.</p> 980 981<p><b>The workaround:</b> To provide version-specific resources, abide by this behavior. However, 982because this bug is fixed in versions of Android available after 1.6, if 983you need to differentiate resources between Android 1.5, 1.6, and later versions, then you only need 984to apply the version qualifier to the 1.6 resources and one to match all later versions. Thus, this 985is effectively a non-issue.</p> 986 987<p>For example, if you want drawable resources that are different on each Android 1.5, 1.6, 988and 2.0.1 (and later), create three drawable directories: {@code drawable/} (for 1.5 and lower), 989{@code drawable-v4} (for 1.6), and {@code drawable-v6} (for 2.0.1 and later—version 2.0, v5, 990is no longer available).</p> 991 992 993