How to write Exif Data using custom Camera Class in android?

I have a custom camera application that is used to take pictures and crop them to square, now I want to know how to write Exif data for the final output image (specially the orientation)

Here are the important parts of my code:

captureButton = (Button) findViewById(R.id.button_capture);
    captureButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // Take a picture
            mCamera.takePicture(null, null, mPicture);                                
        }
    });

and this is the call back function:

PictureCallback mPicture = new PictureCallback() {
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            File pictureFile = getOutputMediaFile();
            if (pictureFile == null) {
                return;
            }
            try {
                FileOutputStream fos = new FileOutputStream(pictureFile);
                fos.write(data);
                fos.close();
            } catch (FileNotFoundException e) {

            } catch (IOException e) {
            }
        }
    };

Update: I Added the following to the onPictureTaken method but nothing changed:

ExifInterface exif;
                exif = new ExifInterface(pictureFile.getAbsolutePath());
// Notice getOrientation method gets an Integer with the angle : 0 , 90 , 180 , 270 ..etc
                exif.setAttribute(ExifInterface.TAG_ORIENTATION, String.valueOf(getOrientation()) );
                exif.saveAttributes();