Hi. I started my task to master Arduino to Android Bluetooth communications 3 years ago. It took ME about 4 months to learn the Android Studio and Java tree structure before I had success to deploy Android application I had written from scratch to connect to Arduino through a HC-05. I use it for my keyless entry, automatic start for my old trucks since I can't stand carrying around keys and losing them anymore.
The Android Studio has extremely poor examples and very vague information - I actually struggled to find active forums with other active programmers.
Never had I struggled so difficult to try to get the BLE 4.0 modules to work with Android. The Android Studio core forces the application to request user permission to a GPS LOCATION (for reasons unknown) just to connect to a BLE device. I tried night and day for months to figure out with little progress and plenty of failure - including
scavenging the internet to find others to help me on the Android side of BLE 4.0
Get BLUETOOTH to work with Arduino is a piece of cake, most the information is there and you can connect to other BLE 4.0 devices, should you be able to figure out the other device to connect to that ISN'T an Arduino.
You can stream music, data, video - do whatever you want - until it disconnects, then prepare for months worth of trial and error to figure out what microwave oven suddenly turned on that interrupted your bluetooth data stream. Then have fun "GRANTING PERMISSIONS" to reconnect to the same BLE device.
Maybe there is new information since November 2016 since I stopped trying, due to my lack of success - I don't know. But I spent a whole bunch of time, trying to learn figure it out - and am very disappointed, and failed. I hope you have better success than me. The tutorials make it sound like "OH YEA JUST CONNECT THESE 5 WIRES, and you can just turn any light on in your house!" but beyond making a light blink, a few times - after the devices refuse to automatically re-connect, is a game I am no longer interested in playing.