this should significantly reduce CPU usage but is a little bit more complicated.
while we're at it, remove the different screen redraw events and use a combined
event for all screens.
TODO:
the spotify player still needs to update the statusbar at least every second.
this is a pretty big but necessary change and might not be stable yet.
some key points:
- the queue is now responsible for playback controls and track management, as
this was scattered between the queue and spotify objects.
- because the queue is now retained, it should be easier to save it as a
spotify playlist
closes#12
- move from listview to linearlayout + scrollview
- doesn't redraw the whole view on queue changes anymore
- uses new cursive functions for linearlayout (needs cursive git)
closes#3
this approach needs some (re)work, as the UI is not fully sync'd with the data,
yet. it'd probably be better to have an event system triggered by the queue,
that will cause a UI refresh or similar.
