Android 2.2 Froyo

Android 2.2 (otherwise known as Froyo, short for Frozen Yogurt) is a version of Android that was released on May 20 2010. Its predecessor was Android 2.1 Eclair and its successor was Android 2.3 Gingerbread. Android 2.2 latest release on November 21 2011 as android 2.2.3. Android 2.2 support ended on October 2 2014.

Linux
Android 2.2 is based on Linux Kernel 2.6.32, which is a bugfix of earlier 2.6 versions, including the Kernel 2.6.29 used for Android 2.0/2.1 Éclair.

Improvements in 2.2

 * Speed, memory, and performance optimizations
 * Additional application speed improvements, implemented through JIT compilation
 * Integration of Chrome's V8 JavaScript engine into the Browser application
 * Support for the Android Cloud to Device Messaging (C2DM) service, enabling push notifications
 * Improved Microsoft Exchange support, including security policies, auto-discovery, GAL look-up, calendar synchronization and remote wipe
 * Improved application launcher with shortcuts to Phone and Browser applications
 * USB tethering and Wi-Fi hotspot functionality
 * Option to disable data access over mobile network
 * Updated Market application with batch and automatic update features
 * Quick switching between multiple keyboard languages and their dictionaries
 * Support for Bluetooth-enabled car and desk docks
 * Support for numeric and alphanumeric passwords
 * Support for file upload fields in the Browser application
 * The browser now shows all frames of animated GIFs instead of just the first frame only
 * Support for installing applications to the expandable memory
 * Adobe Flash support
 * Support for high-PPI displays (up to 320 ppi), such as four-inch 720p screens
 * Gallery allows users to view picture stacks using a zoom gesture

2.2.1

 * The Android 2.2.1 update was released on 18 January 2011, and included a number of bug fixes, security updates, and performance improvements.

2.2.2

 * The Android 2.2.2 update was released on 22 January 2011, and fixed minor bugs, including SMS rooting issues that affected the Google Nexus One.

2.2.3

 * The Android 2.2.3 update was released on 21 November 2011, and consisted of two security patches.

Android 2.2 Phones

 * Google Nexus One *update*
 * Motorola Droid *update*
 * HTC Evo 4G *update*
 * HTC did say that an update would be offered on some phones "sometime in 2010"
 * HTC Desire "update"
 * LG Optimus line
 * Samsung Galaxy 5