Android: Drawing on surfaceview in listview

Question

I have a listview with a few TextViews and a SurfaceView. Most items in the listview are dynamic and depend on data from an external server. I'm using a custom ArrayAdapter to keep track of things. What I want to do is to draw rectangles on the SurfaceView (which essentially is a pretty thick line) and I want all of this to depend on data from the external server.

Everything is working pretty good, however if I scroll in the listview it looks like the the rectangles are being redrawn all the time. Also if I scroll forwards and backwards "very" fast the drawing gets bad, putting rectangles in places where they shouldn't be etc.

Here is my code for the class which draws the rectangles. This class is included in the ArrayAdapter (see code below).

private class drawTimeLine implements Runnable{

    SurfaceView timeLine;
    SurfaceHolder holder;
    Thread thread;
    Boolean locker = true;
    List<MyBooking> bookings;

    public drawTimeLine(SurfaceView timeLine, List<MyBooking> bookings){
        this.timeLine = timeLine;
        this.holder = timeLine.getHolder();
        this.bookings = bookings;
        thread = new Thread(this);
        thread.start();
    }

    @Override
    public void run() {

        while (locker){
            if(!holder.getSurface().isValid()){
                continue;
            }

            Canvas canvas = holder.lockCanvas();
            draw(canvas);
            holder.unlockCanvasAndPost(canvas);
            pause();
        }
    }

    private void draw(Canvas canvas){
        MyBooking booking;
        RectF rectF;
        long X1 = 0;
        long X2 = 0;
        Integer Y1 = 0;
        Integer Y2 = canvas.getHeight();
        Paint paint = new Paint();
        for (int i = 0; i < bookings.size(); i++){
            booking = bookings.get(i);
            try{
                X1 = calculateX1(booking.getStartTime(), canvas.getWidth());
                X2 = calculateX2(booking.getEndTime(), canvas.getWidth());
            } catch (ParseException e){
                //TODO
            }
            rectF = new RectF(X1, Y1, X2, Y2);
            paint.setColor(Color.YELLOW);
            canvas.drawRect(rectF, paint);
        }
        /*rectF = new RectF(0,0,X22++,Y2);
        paint.setColor(Color.YELLOW);
        canvas.drawRect(rectF, paint);*/

    }

Here is the code for the getView method on the ArrayAdapter.

    public View getView(int position, View convertView, ViewGroup parent) {
    DayView dayView = this.getItem(position);
    TextView date;
    ImageView thumb;
    SurfaceView timeLine;
    TextView regNr;
    TextView model;


    if (convertView == null) {
        convertView = inflater.inflate(R.layout.book_item, null);
        date = null;//(TextView) convertView.findViewById(R.id.bookdate);
        timeLine = (SurfaceView) convertView.findViewById(R.id.surfaceView);
        thumb = (ImageView) convertView.findViewById(R.id.thumbnail);
        regNr = (TextView) convertView.findViewById(R.id.reg);
        model = (TextView) convertView.findViewById(R.id.model);
        convertView.setTag(new ViewHolder(date, timeLine, regNr, model, thumb));
    } else {
        ViewHolder holder = (ViewHolder) convertView.getTag();
        date = holder.getDate();
        timeLine = holder.getTimeLine();
        thumb = holder.getThumb();
        regNr = holder.getRegNr();
        model = holder.getModel();
    }
    //date.setText(dayView.getDate());
    //thumb.setImageBitmap(dayView.getThumb());
    regNr.setText(dayView.getRegNr());
    model.setText(dayView.getModel());
    new drawTimeLine(timeLine, dayView.getBookingList);
    return convertView;
}

I'm pretty new to drawing so it might be that this approach is completely wrong. Anyway, if it isn't, how can I stop the rectangles from being redrawn when scrolling?