from this site
Using the resource id, the format is:
"android.resource://[package]/[res id]"
Uri path = Uri.parse("android.resource://com.androidbook.samplevideo/" + R.raw.myvideo);
or, using the resource subdirectory (type) and resource name (filename without extension), the format is:
"android.resource://[package]/[res type]/[res name]"
Uri path = Uri.parse("android.resource://com.androidbook.samplevideo/raw/myvideo");