rename canvas variable
make background bitmap public
add method to check if new image needs to be created
create SharedPreferences to check if image needs to be updated
remove unused method
split changebitmap method into two
comment out postDelayed, reduces flickering
consolidate checking into one method
add bitmap chaching ability
remove setting background to null and recycling
change min sdk level from 7 to 12
remove unused imports
store cached bitmaps with a more unique key, based on hour and dimensions
add his res images of backgrounds
move images to xhdpi folder instead of xxhdpi
remove unused code
refactor visible boolean code
add javadoc comments