Known issue: scrolling a zoomed-in chart interferes with swiping to the
next/previous chart (so far there's just one, but...)
Workaround: Swipe down and then left or right in one go, this will let
you scroll the zoomed chart
- one fragment per chart screen
- common chart code should move to fragment baseclass and the host
Activity (ChartsActivity)
Currently it's not used, change ControlCenter to invoke ChartsActivity
instead of SleepChartActivity to test it.
WIP for #79
