put disk access into background thread?

Hi, I'm doing research on performance for Android apps. I found some event handlers access disk (read/write files, decode bitmap) from UI thread, but Android docs suggest us to avoid such blocking calls in UI thread. Do they lead to any responsiveness issues?

I tried to refactoring by putting them into background tasks. Looking forward to see your comments.
Doing some testing with 'don't keep activities' from developer settings on, and getting an IndexOutOfBoundsException on line 472 due to the onPageSelected trying to resume position before photos have been deserialised.  Have you tested these changes?