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User Interface Guidelines

Icon Design Guidelines and Android Icon Templates Pack »
Your applications need a wide variety of icons, from a launcher icon to icons in menus, dialogs, tabs, the status bar, and lists. The Icon Guidelines describe each kind of icon in detail, with specifications for the size, color, shading, and other details for making all your icons fit in the Android system. The Icon Templates Pack is an archive of Photoshop and Illustrator templates and filters that make it much simpler to create conforming icons.
Widget Design Guidelines
A widget displays an application's most important or timely information at a glance, on a user's Home screen. These design guidelines describe how to design widgets that fit with others on the Home screen. They include links to graphics files and templates that will make your designer's life easier.