Remove spacing between items in RecyclerView android

just remove the cardview in your layout/cardview_recycler.xml, android puts that spacing that you don't want

<LinearLayout
    android:id="@+id/content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <mypackagename.ui.view.RecyclingImageView
        android:id="@+id/avatar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:scaleType="fitXY"
        android:adjustViewBounds="true"
        android:src="@drawable/img_no_avatar" />

    <TextView
        android:id="@+id/username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center_vertical"
        android:singleLine="true"
        android:ellipsize="end"
        android:padding="@dimen/spacing"
        android:textColor="@color/black"
        android:layout_alignParentBottom="true"
        android:textSize="@dimen/text_smallest" />
</LinearLayout>

everything else stays as it is

Give android:layout_height = wrap_content instead of match_parent to your item root layout

<android.support.v7.widget.CardView
        android:id="@+id/card_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
       -------
       -------
</android.support.v7.widget.CardView>