this link explains how to do it more clearly
http://csie-tw.blogspot.in/2009/06/android-driving-direction-route-path.html
Are you aware of google earth kml ?
https://developers.google.com/kml/documentation/kml_tut
I used it once to plot route from 1 point to another on google map. once you parse it you can plot these points as
mapView.getProjection().toPixels(start, screenPts);
//---add the marker---
Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.pin);
canvas.drawBitmap(bmp, screenPts.x, screenPts.y, null);
Point screenPts2 = new Point();
mapView.getProjection().toPixels(end, screenPts2);
//---add the marker---
Bitmap bmp2 = BitmapFactory.decodeResource(getResources(), R.drawable.pin);// pin is a resource you have to add
canvas.drawBitmap(bmp2, screenPts2.x, screenPts2.y, null);