Storing Image Files for the UniversalResHandler

When using the UniversalResHandler resource handler, you need to store image files in a specific folder structure. The required folder structure is automatically created for a project when you create the project using the Mobile Development New Mobile Development Project wizard, as described in Creating a New Mobile Project.

The structure allows you to supply different image files for different platforms. For example, if a mobile application uses an image file named myimage.png, you might need one version of the image file for an Android device and a different version for an iOS device. The folder structure allows you to save both, and at run time the application selects the correct image file based on the device on which the mobile application is running.

The folder structure has platform-specific folders and a single general-purpose folder. Use the general-purpose folder to save image files that can be used for devices running on any platform. The following shows an example for a project named "MyProject":

Additionally, each of the main image folders (Android, iOS, WinPhone, and general) contain subfolders themselves. This allows you to supply different image files for different devices within a platform. For example, if a mobile application uses an image file named myimage.png, you might need one version of the image file for an iOS non-retina device and a different version for an iOS retina device. The following table describes the subfolder structure for each main image folder:

Main image folder	Description of its subfolder structure
Android	The subfolders are based on screen density of Android device on which the mobile application runs. The following shows the subfolder structure: Android drawable-hdpi drawable-ldpi drawable-mdpi drawable-xhdpi drawable-xxhdpi
iOS	The subfolders are based on the display property of the iOS device, either non-retina or retina. The following shows the subfolder structure: iOS NonRetina Retina RetinaHD
WinPhone	The subfolders are based on the screen resolution of the Windows Phone device and whether background color of the view in which the image is displayed is dark or light. The following shows the subfolder structure: WinPhone Dark 1080p 720p WVGA WXGA Light 1080p 720p WVGA WXGA
general	The subfolders are based on the width (in pixels) of the container in which the image is displayed at run time. For example, the container might a view or table cell. The following shows the subfolder structure: general w200 w400 w600 w800

2. Platform-specific root folder. Continuing with the example, if the image was not found in the platform-specific subfolder, the application next looks for the image in the platform-specific root folder, which is resources/graphics/iOS/ folder.

3. General subfolder. Continuing with the example, if the image was not found in the platform-specific root folder, the application next looks for the image in the appropriate general subfolder. For example, if the image is to be displayed in a table cell that is 150 pixels, the application looks for the image file in the resources/graphics/general/w200/ folder.

4. General folder. Continuing with the example, if the image was not found in the general subfolder, the application next looks for the image in the general root folder, which is resources/graphics/general/ folder.