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2.8  Key 
Key assignment 
The assignment of function buttons is as follows. 
 
KEY Function  Android Key Event 
 
Switching Applications 
  Touch to switch to the recent used applications. 
This key is also called as “Recent Apps key”. 
KEYCODE_APP_SWITCH 
 
Home key 
  From any application or screen, touch to return to the 
Home screen. 
  Touch and hold to open "Now on Tap". 
KEYCODE_HOME 
 
Back Key 
  Touch to go back to the previous screen, or to close a 
  dialog box, options menu, the notification panel, etc. 
KEYCODE_BACK 
 
Function key 
  Touch to slect the function you want to set as the 
shotcut of program buttons. 
KEYCODE_FUNCTION 
 
Power key 
  Press: Lock the screen/Light up the screen. 
  Press and hold: Show the pop-up menu to select from 
Power off/Reboot/Airplane mode/Hot Swap. 
  Press the Power key and Volume down key for more 
than 12s to reset. 
  Press the Power key and Volume down key to capture 
a screenshot. 
KEYCODE_POWER 
 
 
Volume Up key / Volume Down key 
  In call mode, adjusts the headset volume. 
  In Music/Video/Streaming mode, adjusts the media 
volume. 
  In general mode, adjusts the ringtone volume. 
  Mutes the ringtone of an incoming call. 
  In camera preview mode, press Volume up or down 
key to enter burst shoot. 
KEYCODE_VOLUME_UP 
KEYCODE_VOLUME_DOWN
 
Left Triger key 
 
 
Right Trigger key 
 
 
For details of the Android standard library, refer Android official website such as "Android 
Developers".