Dropping event due to window no focus

Question

I am getting this warning but not able to catch reason ?

Dropping event due to no window focus: 
KeyEvent { action=ACTION_DOWN, keyCode=KEYCODE_BACK, scanCode=158, metaState=0,
flags=0x8, repeatCount=0, eventTime=1057872, downTime=1057872, deviceId=4,
displayId=0, source=0x101 }

Can anybody explain, What's the reason for this Warning?

Answer 1

This is perfectly normal if you take any action in response to this event that causes your window to lose focus. It's not a problem.

Note however that it is generally good policy to respond to ACTION_UP for KEYCODE_BACK, not ACTION_DOWN.