Add preprateTessData-method to CameraActivity

CameraActivity.java

// public class CameraActivity extends AppCompatActivity implements CameraBridgeViewBase.CvCameraViewListener {...
//
//  define a constant of the needed subfolder
    public static final String TESS_DATA = "/tessdata";
//
//  private static final String TAG = "CameraActivity";
//...
//  protected void onCreate(Bundle savedInstanceState) {...
//...
//     Call method in onCreate before you create a MyTessOCR instance
       prepareTessData();
//
//     mTessOCR = new MyTessOCR(this);
//...
// }
//...
//...
    // prepare the traineddata on the device (this is not inside of the onCreate method)
    private void prepareTessData() {
        try {
            File dir = getExternalFilesDir(TESS_DATA);
            if (!dir.exists()) {
                if (!dir.mkdir()) {
                    Toast.makeText(getApplicationContext(), "The folder " + dir.getPath() + "was not created", Toast.LENGTH_SHORT).show();
                }
            }
            String fileList[] = getAssets().list("tessdata");

            for (String fileName : fileList) {
                String pathToDataFile = dir + "/" + fileName;
                if (!(new File(pathToDataFile)).exists()) {
                    InputStream in = getAssets().open("tessdata/" + fileName);
                    OutputStream out = new FileOutputStream(pathToDataFile);
                    byte[] buff = new byte[1024];
                    int len;
                    while ((len = in.read(buff)) > 0) {
                        out.write(buff, 0, len);
                    }
                    in.close();
                    out.close();
                }
            }
        } catch (Exception e) {
            Log.e(TAG, e.getMessage());
        }
    }
//...
//}