Android 在cardview上定位浮动按钮

我试图在cardview上锚定一个浮动按钮，但没有成功

<?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="wrap_content"
    android:orientation="vertical">


    <android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:card_view="http://schemas.android.com/apk/res-auto"
        android:id="@+id/card_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="4dp"
        android:layout_marginLeft="4dp"
        android:layout_marginRight="4dp"
        android:layout_marginTop="8dp"
        android:background="@android:color/white"
        card_view:cardCornerRadius="2dp"
        card_view:cardElevation="2dp">


            ..... my view ...


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

    <android.support.design.widget.FloatingActionButton
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        app:layout_anchor="@id/card_view"
        app:layout_anchorGravity="bottom|end|right"
        android:layout_margin="16dp"
        android:clickable="true"/>

</LinearLayout>

我希望浮动按钮显示为绿色圆圈。
此布局用于RecyclerView

这是实现这一目标的一种方法吗？
在发布问题之前，谷歌搜索了一下，第二个结果是这样的

编辑

我在一个单独的项目中实现了这一点，效果很好

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

<android.support.v4.widget.NestedScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >

    <android.support.v7.widget.CardView
        android:id="@+id/cv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="16dp">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="The Android Support Library package is a set of code libraries that provide backward-compatible versions of Android framework APIs as well as features that are only available through the library APIs. Each Support Library is backward-compatible to a specific Android API level. This design means that your applications can use the libraries' features and still be compatible with devices running Android 1.6 (API level 4) and up." />

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

</android.support.v4.widget.NestedScrollView>

<android.support.design.widget.FloatingActionButton
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"
    app:layout_anchor="@id/cv"
    app:layout_anchorGravity="right|end|bottom"
    android:layout_marginRight="32dp"
    android:clickable="true"/>

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

您可以在浮动按钮下面添加代码吗

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"

>

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="200dp"
    android:orientation="vertical"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_marginBottom="297dp"
    android:id="@+id/relativeLayout">


    <android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:card_view="http://schemas.android.com/apk/res-auto"
        android:id="@+id/card_view"
        android:layout_width="match_parent"
        android:layout_height="fill_parent"
        android:layout_marginBottom="4dp"
        android:layout_marginLeft="4dp"
        android:layout_marginRight="4dp"
        android:layout_marginTop="8dp"

        android:background="@android:color/white"
        card_view:cardCornerRadius="2dp"
        card_view:cardElevation="2dp">


        ..... my view ...


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

</RelativeLayout>

<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom|end"
    app:srcCompat="@android:drawable/ic_dialog_email"
    android:layout_marginRight="12dp"
    android:layout_marginEnd="12dp"
    android:layout_marginTop="165dp"
    android:layout_alignTop="@+id/relativeLayout"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true" />


..... 我的看法。。。

将整个布局包装在
协调布局中
并定义卡视图的定位点

app:layout_anchor="@id/card_view"
app:layout_anchorGravity="bottom|end|right"

然后它应该会起作用。
只要在你的浮动操作按钮中添加这一行android:layout_gravity=“center | bottom | right”，如果它不起作用，我会帮助它，这不是诀窍。我将浮动按钮放在右边，但不是像绿色圆圈一样固定在cardview边框上。你肯定错过了什么，这段代码本身的行为完全符合您的需要和我们的期望