从android资源获取MIME类型？

Question

如何从android资源URI获取MIME类型？

URI看起来像：

android.resource://com.package.name/drawable/resourceName

我试过

ContentResolver cR = context.getContentResolver();
MimeTypeMap mime = MimeTypeMap.getSingleton();
mimetype = mime.getExtensionFromMimeType(cR.getType(uri));

但返回的MIME类型为null

和

String url = uri.toString();
String extension = MimeTypeMap.getFileExtensionFromUrl(url);
mimetype = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);

但没有延期...