Use Following code.
<?xml version="1.0" encoding="utf-8"?> <ripple android:color="@color/COLOR_WHILE_PRESSING" xmlns:android="http://schemas.android.com/apk/res/android"> <item android:drawable="@drawable/round_corner"></item> </ripple>

round_corner.xml

<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android"> <solid android:color="@color/BACKGROUND_COLOR" /> <corners android:radius="6dp" /> </shape>

Try that one:
ripple.xml
<?xml version="1.0" encoding="utf-8"?> <ripple android:color="@color/COLOR_WHILE_PRESSING" xmlns:android="http://schemas.android.com/apk/res/android"> <item android:drawable="@drawable/background"></item> </ripple>

background.xml
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android"> <solid android:color="@color/BACKGROUND_COLOR" /> <corners android:radius="6dp" /> </shape>

Or maybe this post will help you: https://stackoverflow.com/questions/24480425/android-l-fab-button-shadow/24498041#24498041
I explained there, how to implement the new FAB button, I also used the outline for that.