CopyTask function copies empty file from usb to internal storage.

This is the function from where file is copied

UsbMassStorageDevice[] devices = UsbMassStorageDevice.getMassStorageDevices(getActivityContext() /* Context or Activity */);
        for (UsbMassStorageDevice device : devices) {

            // before interacting with a device you need to call init()!
            //considering only one device is inserted in every case
            try {
                device.init();
                // Only uses the first partition on the device
                FileSystem currentFs = device.getPartitions().get(0).getFileSystem();
                UsbFile folder = currentFs.getRootDirectory().search(sBackupFolder).search(folderName);
                if (folder == null) {
                    Utilities.Toaster(getActivityContext(), "Backup folder not found");
                } else {
                    Utilities.Toaster(getActivityContext(), "Backup folder found. Checking for files");
                    folder.listFiles();
                    int fileCount = 0;
                    List<String> list = new ArrayList<>();
                    if (folder.list() != null) {
                        for (int i = 0; i < folder.listFiles().length; i++) {
                            UsbFile backupFile = folder.listFiles()[i];
                            if (backupFile.getName().equals("DB1V" + DaoMaster.SCHEMA_VERSION + "Backup.db") || backupFile.getName().equals("DB2V" + 3 + "Backup.db")) {
                                fileCount++;
                            }
                        }
                        if (fileCount < 2)
                            Utilities.Toaster(getActivityContext(), "Backup files missing");
                        else {
                            //todo copy db to desired location
                            Utilities.Toaster(getActivityContext(), "Backup files found");
                            for (int i = 0; i < folder.listFiles().length; i++) {
                                UsbFile backupFile = folder.listFiles()[i];
                                if (backupFile.getName().equals("DB1V" + DaoMaster.SCHEMA_VERSION + "Backup.db")) {
                                    //copy greenDB to app folder
                                    CopyTaskParam sourceDestination = new CopyTaskParam();
//                                    File dbFile = new File(getActivityContext().getDatabasePath("green-db").getPath());
                                    File dbFile = new File(Environment.getExternalStorageDirectory()+"/green.db");
                                    sourceDestination.from = backupFile;
                                    sourceDestination.to = dbFile;

                                    new CopyTask(getActivityContext()).execute(sourceDestination);

                                }
                              /*  if (backupFile.getName().equals("DB2V" + 3 + "Backup.db")) {
                                    //copy sugarDB to app folder
                                    CopyTaskParam sourceDestination = new CopyTaskParam();
                                    File dbFile = new File(getActivityContext().getDatabasePath("syntech_tabletbanking.db").getPath());
                                    sourceDestination.from = backupFile;
                                    sourceDestination.to = dbFile;
                                    new CopyTask(getActivityContext()).execute(sourceDestination);
                                }*/
                            }
                        }

                    } else {
                        Utilities.Toaster(getActivityContext(), "Backup files missing");
                    }
                    setupRecyclerView(list);
                }
                device.close();
            } catch (IOException | NullPointerException e) {
                e.printStackTrace();
                new Handler().postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(getActivityContext(), "Restore failed " + e.toString(), Toast.LENGTH_SHORT).show();
                        unregisterReceiver(mUsbReceiver);
                        dialog.dismiss();
                    }
                }, 3000);
            }
        }

This is the file I created from your reference.

public class CopyTask extends AsyncTask<CopyTaskParam, Integer, Void> {

    private ProgressDialog dialog;
    private CopyTaskParam param;
    private Context context;

    public CopyTask(Context context) {
        this.context = context;
        dialog = new ProgressDialog(context);
        dialog.setTitle("Copying file");
        dialog.setMessage("Copying a file to the internal storage, this can take some time!");
        dialog.setIndeterminate(true);
        dialog.setCancelable(false);
    }

    @Override
    protected void onPreExecute() {
        dialog.show();
    }

    @Override
    protected Void doInBackground(CopyTaskParam... params) {
        long time = System.currentTimeMillis();
        param = params[0];
        try {
            OutputStream out = new BufferedOutputStream(new FileOutputStream(param.to));

            Log.d("TAG", "Copy file with length: " + param.from.getLength());
            out.write(convertIntoBytes(param.from.getAbsolutePath()));
            out.close();
        } catch (IOException e) {
            Log.e("TAG", "error copying!", e);
        }
        Log.d("TAG", "copy time: " + (System.currentTimeMillis() - time));
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        dialog.dismiss();
        Utilities.Toaster(context, "Database Restored");
    }

    private byte[] convertIntoBytes(String db) {
        try {
            File dbFile = new File(db);
            FileInputStream fis = new FileInputStream(dbFile);
            // Transfer bytes from the input file to the output file
            byte[] bytesArray = new byte[(int) dbFile.length()];
            fis.read(bytesArray);
            fis.close();
            return bytesArray;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }
}

[magnusja]

Ok interesting. Then I will close this for now, reopen if you encounter this again.

[SynergySaugat]

currently i have solved the issue from a different approach… I converted the UsbFile into bytearray ani wrote it into internal storage so it works now… Thankyou for your feedback 😄 I read your thesis also… Had a great help from there too.