I'm using Android Studio I/O(Preview) 0.3.2 I'm using this example to define background gradient in my app. I get Element must be declared error. I've checked and I'm not find any solutions. Can anyone help me how can I declare that tag in the xml

Element must be declared error for tag shape

I'm using Android Studio I/O(Preview) 0.3.2

I'm using this example to define background gradient in my app. I get Element must be declared error. enter image description here

I've checked and I'm not find any solutions. Can anyone help me how can I declare that tag in the xml