在Android系统中有一些索引，每当他们下载或移动到系统存储时索引ALM媒体文件？ 我猜我在Android系统和应用程序之外有一些索引。 因为当在我的下载文件夹中首次下载MP3文件时，该应用程序就可以发现它。 但是如果我使用第三方应用程序并转移到另一个文件夹（谷歌音乐播放有权访问），谷歌音乐播放WLL仍然识别仍然存在于删除文件夹中的MP3文件并在尝试播放歌曲时显示错误。
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.
My guess is it's associated with mediastore, a content provider in Android system. Check this for information.