在运行时创建CardView不起作用？

Question

我有以下代码：

CardView card = new CardView(new ContextThemeWrapper(this, R.style.CardView), null, 0);
card.setLayoutParams(new LinearLayout.LayoutParams(
    LinearLayout.LayoutParams.MATCH_PARENT,
    LinearLayout.LayoutParams.MATCH_PARENT
));
resultsLayout.addView(card);

XML：

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:id="@+id/resultsLayout"
    tools:context="com.xyz.ResultsActivity">
</RelativeLayout>

但这不显示卡？有人可以帮忙吗？