问为什么棒棒糖上的CardViews之间没有空格？

EN

<?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"
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.support.v7.widget.CardView android:layout_width="match_parent"
    android:layout_height="200dp">
    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="card1"
        android:textAppearance="?android:attr/textAppearanceLarge" />
</android.support.v7.widget.CardView>
<android.support.v7.widget.CardView android:layout_width="match_parent"
    android:layout_height="200dp">

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="card2"
        android:textAppearance="?android:attr/textAppearanceLarge" />
</android.support.v7.widget.CardView>
</LinearLayout>