docs: public static File getRootStorageDirectory(Context c, String directory_name){
          File result;
          // First, try getting access to the sdcard partition
          if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
              Log.d(TAG,"Using sdcard");
              result = new File(Environment.getExternalStorageDirectory(), directory_name);
          } else {
              // Else, use the internal storage directory for this application
              Log.d(TAG,"Using internal storage");
              result = new File(c.getApplicationContext().getFilesDir(), directory_name);
          }
  
          if(!result.exists())
              result.mkdir();
          else if(result.isFile()){
              return null;
          }
          Log.d("getRootStorageDirectory", result.getAbsolutePath());
          return result;
      }