RecyclerView嵌套RecyclerView只显示一行

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<!--话题-->
<TextView
android:id="@+id/tv_topic_name"
android:layout_width="match_parent"
android:layout_height="45dp"
android:gravity="center"
android:paddingBottom="31px"
android:paddingTop="31px"
android:text="#话题#"
android:textColor="@color/color_333333"
android:textSize="40px" />

</LinearLayout>