首页 > 代码库 > Android寻找匹配最佳资源的原理
Android寻找匹配最佳资源的原理
drawable/ drawable-en/ drawable-fr-rCA/ drawable-en-port/ drawable-en-notouch-12key/ drawable-port-ldpi/ drawable-port-notouch-12key/并且假设,系统的配置如下:
en-GB
Screen orientation =
port
Screen pixel density =
hdpi
Touchscreen type =
notouch
Primary text input method =
12key
- 同样,以上面的例子为例,Android会首先去除与设备当前配置不符的文件目录。在这个例子中, drawable-fr-rCA/ 文件被消除,因为它与语言位置 en-GB 不符。由此,剩下的结果如下:
drawable/ drawable-en/drawable-fr-rCA/drawable-en-port/ drawable-en-notouch-12key/ drawable-port-ldpi/ drawable-port-notouch-12key/
- 接着,系统会按照优先级顺序对适配条件(qualifier)进行判定(步骤2)
- 进入步骤3,如果无法满足步骤2中的当前适配条件,则换下一个适配条件继续步骤2;如果有文档目录满足当前的失配条件,则进入步骤4
- 排除剩下目录中,不符合当前适配条件的目录。在本例子中,适配条件为英语语种(en)时,剩下的结果如下,不符合这一条件的目录被排除
drawable/drawable-en/ drawable-en-port/ drawable-en-notouch-12key/drawable-port-ldpi/ drawable-port-notouch-12key/
- 最后,重复步骤2, 3, 4得到唯一的目录,最终结果如下:
drawable-en/drawable-en-port/drawable-en-notouch-12key/
Table 2. Configuration qualifier names.
Configuration | Qualifier Values | Description |
---|---|---|
MCC and MNC | Examples:mcc310
mcc310-mnc004 mcc208-mnc00 etc. | The mobile country code (MCC), optionally followed by mobile network code (MNC) from the SIM card in the device. For example, If the device uses a radio connection (GSM phone), the MCC and MNC values come from the SIM card. You can also use the MCC alone (for example, to include country-specific legal resources in your application). If you need to specify based on the language only, then use the language and region qualifier instead (discussed next). If you decide to use the MCC and MNC qualifier, you should do so with care and test that it works as expected. Also see the configuration fields |
Language and region | Examples:en fr en-rUS fr-rFR fr-rCA etc. | The language is defined by a two-letter ISO 639-1 language code, optionally followed by a two letter ISO 3166-1-alpha-2 region code (preceded by lowercase " The codes are not case-sensitive; the This can change during the life of your application if the user changes his or her language in the system settings. See Handling Runtime Changes for information about how this can affect your application during runtime. See Localization for a complete guide to localizing your application for other languages. Also see the |
Layout Direction | ldrtl ldltr | The layout direction of your application. This can apply to any resource such as layouts, drawables, or values. For example, if you want to provide some specific layout for the Arabic language and some generic layout for any other "right-to-left" language (like Persian or Hebrew) then you would have: res/ layout/ main.xml (Default layout) layout-ar/ main.xml (Specific layout for Arabic) layout-ldrtl/ main.xml (Any "right-to-left" language, except for Arabic, because the "ar" language qualifier has a higher precedence.) Note: To enable right-to-left layout features for your app, you must set Added in API level 17. |
smallestWidth | sw<N>dp Examples: sw320dp sw600dp sw720dp etc. | The fundamental size of a screen, as indicated by the shortest dimension of the available screen area. Specifically, the device‘s smallestWidth is the shortest of the screen‘s available height and width (you may also think of it as the "smallest possible width" for the screen). You can use this qualifier to ensure that, regardless of the screen‘s current orientation, your application has at least For example, if your layout requires that its smallest dimension of screen area be at least 600 dp at all times, then you can use this qualifer to create the layout resources, The smallestWidth of a device takes into account screen decorations and system UI. For example, if the device has some persistent UI elements on the screen that account for space along the axis of the smallestWidth, the system declares the smallestWidth to be smaller than the actual screen size, because those are screen pixels not available for your UI. Thus, the value you use should be the actual smallest dimension required by your layout (usually, this value is the "smallest width" that your layout supports, regardless of the screen‘s current orientation). Some values you might use here for common screen sizes:
When your application provides multiple resource directories with different values for the smallestWidth qualifier, the system uses the one closest to (without exceeding) the device‘s smallestWidth. Added in API level 13. Also see the For more information about designing for different screens and using this qualifier, see the Supporting Multiple Screens developer guide. |
Available width | w<N>dp Examples: w720dp w1024dp etc. | Specifies a minimum available screen width, in When your application provides multiple resource directories with different values for this configuration, the system uses the one closest to (without exceeding) the device‘s current screen width. The value here takes into account screen decorations, so if the device has some persistent UI elements on the left or right edge of the display, it uses a value for the width that is smaller than the real screen size, accounting for these UI elements and reducing the application‘s available space. Added in API level 13. Also see the For more information about designing for different screens and using this qualifier, see the Supporting Multiple Screens developer guide. |
Available height | h<N>dp Examples: h720dp h1024dp etc. | Specifies a minimum available screen height, in "dp" units at which the resource should be used—defined by the When your application provides multiple resource directories with different values for this configuration, the system uses the one closest to (without exceeding) the device‘s current screen height. The value here takes into account screen decorations, so if the device has some persistent UI elements on the top or bottom edge of the display, it uses a value for the height that is smaller than the real screen size, accounting for these UI elements and reducing the application‘s available space. Screen decorations that are not fixed (such as a phone status bar that can be hidden when full screen) are notaccounted for here, nor are window decorations like the title bar or action bar, so applications must be prepared to deal with a somewhat smaller space than they specify. Added in API level 13. Also see the For more information about designing for different screens and using this qualifier, see the Supporting Multiple Screens developer guide. |
Screen size | small normal large xlarge |
Note: Using a size qualifier does not imply that the resources areonly for screens of that size. If you do not provide alternative resources with qualifiers that better match the current device configuration, the system may use whichever resources are the best match. Caution: If all your resources use a size qualifier that is larger than the current screen, the system will not use them and your application will crash at runtime (for example, if all layout resources are tagged with the Added in API level 4. See Supporting Multiple Screens for more information. Also see the |
Screen aspect | long notlong |
Added in API level 4. This is based purely on the aspect ratio of the screen (a "long" screen is wider). This is not related to the screen orientation. Also see the |
Screen orientation | port land |
This can change during the life of your application if the user rotates the screen. See Handling Runtime Changes for information about how this affects your application during runtime. Also see the |
UI mode | car desk television |
Added in API level 8, television added in API 13, watch added in API 20. For information about how your app can respond when the device is inserted into or removed from a dock, read Determining and Monitoring the Docking State and Type. This can change during the life of your application if the user places the device in a dock. You can enable or disable some of these modes using |
Night mode | night notnight |
Added in API level 8. This can change during the life of your application if night mode is left in auto mode (default), in which case the mode changes based on the time of day. You can enable or disable this mode using |
Screen pixel density (dpi) | ldpi mdpi hdpi xhdpi xxhdpi xxxhdpi nodpi tvdpi |
There is a 3:4:6:8:12:16 scaling ratio between the six primary densities (ignoring the tvdpi density). So, a 9x9 bitmap in ldpi is 12x12 in mdpi, 18x18 in hdpi, 24x24 in xhdpi and so on. If you decide that your image resources don‘t look good enough on a television or other certain devices and want to try tvdpi resources, the scaling factor is 1.33*mdpi. For example, a 100px x 100px image for mdpi screens should be 133px x 133px for tvdpi. Note: Using a density qualifier does not imply that the resources areonly for screens of that density. If you do not provide alternative resources with qualifiers that better match the current device configuration, the system may use whichever resources are the best match. See Supporting Multiple Screens for more information about how to handle different screen densities and how Android might scale your bitmaps to fit the current density. |
Touchscreen type | notouch finger |
Also see the |
Keyboard availability | keysexposed keyshidden keyssoft |
If you provide This can change during the life of your application if the user opens a hardware keyboard. See Handling Runtime Changes for information about how this affects your application during runtime. Also see the configuration fields |
Primary text input method | nokeys qwerty 12key |
Also see the |
Navigation key availability | navexposed navhidden |
This can change during the life of your application if the user reveals the navigation keys. See Handling Runtime Changes for information about how this affects your application during runtime. Also see the |
Primary non-touch navigation method | nonav dpad trackball wheel |
Also see the |
Platform Version (API level) | Examples:v3 v4 v7 etc. | The API level supported by the device. For example, |
Android寻找匹配最佳资源的原理