I am trying to make a view in android with rounded edges. The solution I found so far is to define a shape with rounded corners and use it as the background of that view.
The CardView worked for me in API 27 in Android Studio 3.0.1. The colorPrimary was referenced in the res/values/colors.xml file and is just an example. For the layout_width of 0dp it will stretch to the width of the parent. You'll have to configure the constraints and width/height to your needs.