Android has a highly organized, hierarchical approach to their UI Design, Get Started -Creative Vision -Design Principles -UI Overview
Style -Devices and Displays -Themes -Touch Feedback -Metrics and Grids -Typography -Color -Iconography -Writing Style Patterns -New -Gestures -App Structure -Navigation -Action Bar -Multi-pane Layouts -Swipe Views -Selection -Notifications -Compatibility -Pure Android Building Blocks -Tabs -Lists -Grid Lists -Scrolling -Spinners -Buttons -Text Fields -Seek Bars -Progress & Activity -Switches -Dialogs -Pickers [1] http://developer.android.com/design/index.html
