android - Why Recyclerview not Scrolls when its height is taken match parent in below xml? -

<?xml version="1.0" encoding="utf-8"?> <relativelayout xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="match_parent"     android:layout_height="match_parent"     xmlns:app="http://schemas.android.com/apk/res-auto"     android:background="#fff"      >      <linearlayout         android:id="@+id/linear_layout_id"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:background="@color/colorprimary"         android:orientation="horizontal">          <imageview             android:layout_width="0dp"             android:layout_weight="1"             android:layout_height="24dp"             android:src="@drawable/ic_search"             android:layout_margintop="12dp"             android:layout_marginleft="5dp"             android:singleline="true"             />          <edittext             android:id="@+id/autocomplete_places"             android:layout_width="0dp"             android:layout_weight="9"             android:layout_height="50dp"             android:drawablepadding="9dp"             android:hint="@string/autocomplete_hint"             android:paddingleft="5dp"             android:paddingright="9dp"             android:singleline="true"             android:background="@android:color/transparent"             android:textcolor="#fff"             android:textcolorhint="@color/white"             android:visibility="visible" />          <imageview             android:id="@+id/cross"             android:singleline="true"             android:layout_weight="1"             android:layout_width="0dp"             android:layout_height="24dp"             android:src="@drawable/ic_clear"             android:layout_marginright="7dp"             android:layout_margintop="12dp"             android:visibility="gone"             />      </linearlayout>     <relativelayout         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_below="@+id/linear_layout_id"         android:id="@+id/pick_position_layout_id"         android:padding="4dp"         android:background="@color/window_background"         >          <android.support.v7.widget.cardview             android:layout_width="match_parent"             android:layout_height="wrap_content"             app:cardcornerradius="4dp"             android:elevation="4dp">              <linearlayout                 android:layout_width="match_parent"                 android:layout_height="wrap_content"                 android:orientation="horizontal">                  <imageview                     android:layout_width="wrap_content"                     android:layout_height="20dp"                     android:src="@drawable/ic_gps"                     android:tint="@color/common_action_bar_splitter"                     android:layout_margintop="10dp"                     android:layout_marginleft="10dp"/>             <textview                 android:layout_width="wrap_content"                 android:layout_height="wrap_content"                 android:layout_margin="10dp"                 android:text="use location"/>              </linearlayout>           </android.support.v7.widget.cardview>      </relativelayout>      <android.support.v7.widget.recyclerview         android:id="@+id/recyclerviewid"         android:layout_width="match_parent"         android:layout_height="match_parent"         android:layout_below="@+id/pick_position_layout_id"         android:scrollbars="vertical"/>       <android.support.v7.widget.recyclerview         android:id="@+id/recyclerview"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_below="@+id/linear_layout_id"         android:scrollbars="vertical" /> </relativelayout> 

above complete xml file.my problem when in below recyclerview make height wrap_content scrolls when made match_parent not scroll can tell me reason?

    <android.support.v7.widget.recyclerview         android:id="@+id/recyclerviewid"         android:layout_width="match_parent"         android:layout_height="match_parent"         android:layout_below="@+id/pick_position_layout_id"         android:scrollbars="vertical"/> 

but recyclerview works both match_parent , wrap_content.

    <android.support.v7.widget.recyclerview         android:id="@+id/recyclerview"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_below="@+id/linear_layout_id"         android:scrollbars="vertical" /> 

can tell me reason? in advance :)