It is broke. When you plug a handsfree device into a nexus phone and answer calls from the button of the handsfree, the touchscreen activates.
And if your phone is in your pocket (as it should be when you're running and listening to music) you will close the call in your pocket.
This happens with bluetooth headsets as well. It is the single dumbest, most retarded, behavior in the the history of smartphones. Unless you hold the phone in your hand it is unusable with a hands free. Get the stupidity of it all? You need to hold it in your hand when you use handsfree?
Why are you not fixing this? Why? I've had a nexus 4 from android 4.1 to 4.4. In all these updates you failed to fix this one simple thing. You can use a Nokia 3310 with a headset. Not a nexus device though.
I came back to IOS since then. After only eight months I had to give my nexus 4 away. I ride my bike on my way to work and I was not able to answer calls on the handsfree while the phone was in my pocket, and I did not want to risk my safety by taking the phone out of my pocket when I ride my bike through traffic.
Why? Why do you do this? Why can you not unlock the screen when answering through a headset? It's such a simple feature that ALL non Android phones have had for decades? Why?
This, of course, also makes Google Now useless on an Android device while using a headset.