I've seen this asked before on the forum and the simplest solution is to display your Marker's icon in an ImageView with the ImageView positioned over your MapView's center.
You could instead have a Marker position at the MapView's center and whenever the MapView's position changes, reposition the Marker to the new MapView center.
But you'll see the Marker move with the map and then reposition itself.
With the ImageView solution you'll get exactly what you want.