I did some search these days.
maybe you shoud read these links.
- MediaStore supported MIME type is here: http://androidxref.com/4.4.4_r1/xref/frameworks/base/media/java/android/media/MediaFile.java#174
- And there is also a API URLConnection.getFileNameMap()
- And its inner side is here: http://androidxref.com/4.4.4_r1/xref/libcore/luni/src/main/java/libcore/net/MimeUtils.java