Add loading states
Motivation and Context
For now, no loading indicator is shown when retrieving media lists or file lists
How Has This Been Tested?
Emulator 28 / ADT-2 28
Screenshots / GIFs (if appropriate):
Types of changes
Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Enhancement (non-breaking change which cleans up / improves existing functionality)
Breaking change (fix or feature that would cause existing functionality to change)
I have read the CONTRIBUTING section of the README document.