This application works as MrBeySoftwarePicker Extension Demo application, you can also download Aia File Test APK for free.
MrBeySoftwarePicker Extension Free
Extension Source code Paid Package All new updates available and extension Aix File download Link MrBeySoftware - MrBeySoftwarePicker Extensions
Permissions: You’ll need the READ_EXTERNAL_STORAGE permission to access files. Starting from Android 10 (API level 29), you might also need to request the MANAGE_EXTERNAL_STORAGE permission for broad file access. 
Not needed if you use simple intent to get the uri of selected file and copy it to ASD.
The extension download link is not working
