ChromecastListener has always implemented CastStateListener, but nothing
ever registered it. Whether a receiver was reported as available hung
entirely on the media router callback, which does not always fire - and
then the cast button never appears even though devices are there.
The framework's own signal is registered now and the current state is
reported straight away. It is not taken at face value in one direction:
the framework drops back to NO_DEVICES_AVAILABLE when a session ends,
because it stops discovering at that point, which would hide the button
right after someone stops casting. The devices the media router still
knows decide that case.
The listener is dropped again when the activity goes.
The sleep timer fades playback down to 10% over its last minute by setting the
player's volume. CastPlayer.setVolume was an empty stub and getVolume returned
zero, so while casting the fade did nothing at all.
Both now go through the media stream volume the Cast SDK offers. That is the
receiver's volume for this stream only: the device volume stays where the user
put it, and on a cast group the balance between its members is untouched,
because the receiver applies the stream volume to the group's output.
huggenknubbel