How to center imageView in a ViewPager with matrix scaletype?

I'm using Android Studio and trying to write a Pinch Zooom Class for ViewPager. Zoom is fine, but the image is stuck at the top left corner of the screen. I know that this question has been asked multiple times but I have gone through each one none of them is working for me.

Code:

public class PinchZoom implements View.OnTouchListener {

    public static enum State {Zoom, None}
    private State curentState = State.None;
    private float initialDistance = 0;
    private PointF firstTouchLocation = new PointF();
    private PointF midPoint = new PointF();
    private Matrix matrix = new Matrix();
    private Matrix savedMatrix = new Matrix();
    Context mContext;

    PinchZoom(Context context){
        mContext = context;
    }
    @Override
    public boolean onTouch(View view, MotionEvent motionEvent) {
        int maskedAction = motionEvent.getActionMasked();
        PointF location = new PointF(motionEvent.getX(), motionEvent.getY());
        ImageView imageView= (ImageView) view;

        switch (maskedAction){
            case MotionEvent.ACTION_DOWN:{
                firstTouchLocation.set(location);
                //matrix = imageView.getImageMatrix();
                savedMatrix.set(matrix);
                break;
            }

            case MotionEvent.ACTION_POINTER_DOWN:{
                initialDistance = setDistance(motionEvent);
                if(initialDistance > 20f){
                    setMidPoint(motionEvent);
                    curentState = State.Zoom;
                    savedMatrix.set(matrix);
                }
                break;
            }

            case MotionEvent.ACTION_MOVE:{
                if(curentState == State.Zoom){
                    float currentDistance = setDistance(motionEvent);
                    float scaleFactor = currentDistance / initialDistance;
                    matrix.set(savedMatrix);
                    matrix.postScale(scaleFactor, scaleFactor, midPoint.x, midPoint.y);
                }
                break;
            }

            case MotionEvent.ACTION_UP:{
                curentState = State.None;
                break;
            }

            case MotionEvent.ACTION_POINTER_UP:{
                curentState = State.None;
                break;
            }

        }
        imageView.setImageMatrix(matrix);
        imageView.invalidate();
        return true;
    }

    public float setDistance(MotionEvent event){
        float distX = event.getX() - firstTouchLocation.x;
        float distY = event.getY() - firstTouchLocation.y;
        float distance = (float) Math.sqrt(distX * distX + distY * distY);
        return distance;
    }

    public void setMidPoint(MotionEvent event){
        float x = (event.getX() + firstTouchLocation.x ) / 2;
        float y = (event.getY() + firstTouchLocation.y) / 2;
        midPoint.set(x, y);
    }

}

public class MyPagerAdapter extends PagerAdapter {
    private ArrayList<ImageView> imageViewList;
    private ArrayList<Bitmap> bitmapArrayList;
    private Context mContext;

    public MyPagerAdapter(Context mContext){
        this.mContext = mContext;
    }

    @Override
    public int getCount() {
        return imageViewList.size();
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    @Override
    public Object instantiateItem(ViewGroup parent, int position){
        ImageView imageView = imageViewList.get(position);
        imageView.setScaleType(ImageView.ScaleType.MATRIX);
        imageView.setOnTouchListener(new PinchZoom(mContext));
        if(imageView.getParent() != null){
            ((ViewGroup) imageView.getParent()).removeView(imageView);
        }

        parent.addView(imageView);
        return imageView;
    }

    @Override
    public void destroyItem(ViewGroup parent, int position, Object view){
        imageViewList.remove(position);
    }

    public void setList(ArrayList<Bitmap> list){
        bitmapArrayList = list;
        imageViewList = new ArrayList<>();
        for (Bitmap b : bitmapArrayList) {
            ImageView image = new ImageView(mContext);
            image.setImageBitmap(b);
            imageViewList.add(image);
        }
    }

    public ArrayList<Bitmap> getList(){
        return bitmapArrayList;
    }
}

Thanks!