I managed to get the ripple effect on the cardview by :
<android.support.v7.widget.CardView
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:clickable="true"
android:foreground="@drawable/custom_bg"/>
and for the custom_bg that you can see in above code, you have to define a xml file for both lollipop(in drawable-v21 package) and pre-lollipop(in drawable package) devices. for custom_bg in drawable-v21 package the code is:
<ripple
xmlns:android="http://schemas.android.com/apk/res/android"
android:color="?android:attr/colorControlHighlight">
<item
android:id="@android:id/mask"
android:drawable="@android:color/white"/>
</ripple>
for custom_bg in the drawable package, code is:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true">
<shape>
<solid android:color="@color/colorHighlight"></solid>
</shape>
</item>
<item>
<shape>
<solid android:color="@color/navigation_drawer_background"></solid>
</shape>
</item>
</selector>
so on pre-lollipop devices you will have a solid click effect and on lollipop devices you will have a ripple effect on the cardview.