I would like to learn and know why Google Play Music able to discover all my media file that quick. So I can implement similar functionality for my own app.
In Android system is there some sort of index that indexing alm the media files whenever they got downloaded or moved into system storage? I am guess there is some indexing in Android system and outside of the app. Because when a mp3 file first downloaded in my download folder, the app was able to discover it. But if I use a 3rd party app and moved to another folder (that Google Music Play have access to) , Google Music Play wll still recognize the mp3 file still existing in down folder and show error upon try to play the song.