How this "voice dialer" shows up? Sometimes I'm listening to music on my phone (running Android KitKat), and from my pocket the phone make a sound and the first screenshot shows up and then the second one appears:




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What makes this shows up and how can I stop it?
The Google Now assistant can be activated by long-pressing the button of the earphone, looks like you use the buttons to control music, but is pressing it too long.

Another thing that could be, are you using original earphones? Some earphones, because of incompatibility, keep sending commands even though you are not pressing buttons. Use another earphone for a day and see it the problem occurs, if it doesn't, the problem is in the earphone.