Android allows one application at a time to respond to headset buttons. The application that most recently requested to be the sole receiver of headset button events, will receive all headset button events.
You can see this demonstrated by following these steps:
-Start DoggCatcher and press play in the DoggCatcher UI
-Press a headset button (wired or BT) a few times, DoggCatcher will responds to the button presses
-Start a main stream audio application (like Google Play Music or Spotify) and press play in the music app UI
-Press a headset button (wired or BT) a few times, the music app will responds to the button presses
We've followed the development guidelines and reproduced the intended behavior, and also the behavior of the Android music player.
DoggCatcher will begin responding to the headset buttons when the following happens, and will continue to respond to headset button events until another app requests to be the sole received of headset button events.
-DoggCatcher is launched
-The play button in the DoggCatcher UI is pressed
Headset button developer guidelines
The coding details can be found here - http://android-developers.blogspot.com/2010/06/allowing-applications-to-...
Some devices support the display of Bluetooth meta data, like artist name, track name, etc, on the display of the Bluetooth device.
This works on most devices regardless of DoggCatcher's configuration, however some devices require that the this DoggCatcher setting be enabled:
Settings / Headset/Lockscreen / Lock screen buttons