I had the same problem than Williams in this post, and the solution provided by SceLus worked very well !
However, i'm facing another problem : the shape works correctly on my devices (Nexus 5 and 7 on 4.4.4), but when I test it on a Galaxy Tab 3 (running on 4.1.2), it doesn't work : i have a square shape instead of a hexagon shape.
Does someone has a idea about what causes this problem (It seems the problem come from the Android version because I tried in a Galaxy S2 also on 4.1). What can I do to have the hexagonal shape on devices running on 4.1 ?
Edit : I'm wondering if TouchWiz could be the problem actually...
Edit : view.setLayerType(View.LAYER_TYPE_SOFTWARE, null); did the trick for me. See this post if you have similar problems.