正确地在网格回收器视图项之间放置空格

Question

我有一个带有网格布局管理器的回收站视图：

然后我定义了一个项目装饰的类来在项目之间放置空格，我得到了这个结果：

为什么卡片不能保持尺寸？

这是每个项目的布局：

<android.support.v7.widget.CardView
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/card_view"
    android:layout_width="wrap_content"
    android:layout_height="200dp"
    card_view:cardUseCompatPadding="true"
    card_view:cardCornerRadius="8dp">

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/high_textviewcard"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/breakfast"
        android:textSize="20sp"
        android:textStyle="bold|italic"
        android:gravity="center"/>

    <ImageView
        android:id="@+id/meal_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:scaleType="centerCrop"
        android:gravity="bottom"
        android:layout_below="@+id/high_textviewcard"
        android:paddingTop="8dp"
        android:layout_alignParentBottom="true" />

</RelativeLayout>

这是空间的定义方式：

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
    int position = parent.getChildAdapterPosition(view) - headerNum; // item position

    if (position >= 0) {
        int column = position % spanCount; // item column

        if (includeEdge) {
            outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
            outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

            if (position < spanCount) { // top edge
                outRect.top = spacing;
            }
            outRect.bottom = spacing; // item bottom
        } else {
            outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
            outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
            if (position >= spanCount) {
                outRect.top = spacing; // item top
            }
        }
    } else {
        outRect.left = 0;
        outRect.right = 0;
        outRect.top = 0;
        outRect.bottom = 0;
    }
}

MainActivity布局：

<android.support.v4.widget.DrawerLayout     xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="app.android.com.pappapp.MainActivity">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    android:orientation="vertical">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?attr/colorPrimary"
        android:minHeight="?attr/actionBarSize" />

    <android.support.design.widget.CoordinatorLayout
        android:id="@+id/coordinatorLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <FrameLayout
            android:id="@+id/fragmentContainer"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

        <android.support.v7.widget.RecyclerView
            android:id="@+id/recycler_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:scrollbars="vertical">

        </android.support.v7.widget.RecyclerView>

    </android.support.design.widget.CoordinatorLayout>

</LinearLayout>

<android.support.design.widget.NavigationView
    android:id="@+id/nav_view"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:fitsSystemWindows="true"
    app:headerLayout="@layout/header"
    app:menu="@menu/drawer_menu">


</android.support.design.widget.NavigationView>