3.App Resources-Overview

1. Overview

　　You should always externalize resources such as images and strings from your application code, so that you can maintain them independently.

　　　　Externalizing your resources also allows you to provide alternative resources that support specific device configurations such as different

　　　　languages or screen sizes, which becomes increasingly important as more Android-powered devices become available with different

　　　　configurations. In order to provide compatibility with different configurations, you must organize resources in your project's res/

　　　　directory, using various sub-directories that group resources by type and configuration.

　　For any type of resource, you can specify default and multiple alternative resources for your application:

　　For example, while your default UI layout is saved in the res/layout/ directory, you might specify a different layout to be used when the

　　　　screen is in landscape orientation, by saving it in the res/layout-land/ directory. Android automatically applies the appropriate resources

　　　　by matching the device's current configuration to your resource directory names.

　　<1>Two different devices, each using the default layout (the app provides no alternative layouts).

　　　　 illustrates how the system applies the same layout for two different devices when there are no alternative resources available.

　　 

　　<2>Two different devices, each using a different layout provided for different screen sizes.

　　　　 shows the same application when it adds an alternative layout resource for larger screens.