File Permissions Demo

This project is intended to demonstrate file moving issue on some of the Android M powered devices. The issue is the following:

According to the documentation all files that are stored in the /sdcard/Android/data/<package>/files directory do not require STORAGE permission to have access to it starting from API 19. And it is true if your application creates a file in this directory. But if you move a file from any external storage folder to this application specific external storage directory, this file continue to be inaccessible when STORAGE permission is revoked as it were in the previous folder (on the common external storage).

The issue is reproducible on Android Emulator with Android 6.0 and on Nexus 9 with Android 6.0. On any device or emulator with Android 7.0+ we didn't manage to reproduce it.

How to use it

1. Press "Load" button to download an image to /sdcard/File Permissions directory.
2. Select one of the migration modes:
   • Java to move file from one directory to another with File.renameTo(File)
   • Native to move file with C++ method rename(char*, char*) form stdio.h
   • Copy to copy file content from one directory to another and remove the original file
3. Press "Migrate" button with one of the modes selected to move the downloaded image into /sdcard/Android/data/<package>/files/File Permissions directory
4. Go to app's settings -> Permissions and revoke STORAGE permission
5. Open application again

In the result the image you moved to app's directory with Java or Native migration method won't be loaded when application restored unlike the image that was moved with Copy. So the problem is that on some devices with Android M file owner is transferred after move, but actually it should be changed to the OS user of your application like it happens after copying.