Clone this proyect and import the module "materialCircularButton" in your project
Include the res-auto xmls definition in your parent layout
xmlns:custom="http://schemas.android.com/apk/res-auto"
Then use Like Android ImageButton with two custom attributes:
<com.glomadrian.button.MaterialButton
android:id="@+id/materialButton"
custom:color="#c3c3c3"
custom:transitionTime="1200"
/>
Use the attribute elevation on Material Button to get the full Material Desing (desing)
<com.glomadrian.button.MaterialButton
android:id="@+id/materialButton"
custom:color="#c3c3c3"
custom:transitionTime="1200"
android:elevation="2dp"
/>
###TODO
Upload to maven central...