Ripple effect over a RecyclerView item containing ImageView

add below code to your parent layout

android:clickable="true"
android:focusable="true"
android:background="?attr/selectableItemBackground" 

if you want custom ripple effect add this ripple_custom.xml in your drawable-v21

<?xml version="1.0" encoding="utf-8"?>
<ripple xmlns:android="http://schemas.android.com/apk/res/android"
    android:color="@color/colorHighlight">

    <item
        android:id="@android:id/mask"
        android:drawable="@color/windowBackground" />
</ripple>

to support older version add ripple_custom.xml in drawable

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true">
        <shape android:shape="rectangle">
            <solid android:color="@color/colorHighlight" />
        </shape>
    </item>
    <item>
        <shape android:shape="rectangle">
            <solid android:color="@android:color/transparent" />
        </shape>
    </item>
</selector>