Android layer-list affecting position of floating action button

I am creating an app where a layer-list is used as background and a floating action button is also used. When the layer-list is set as the background of the relative layout, it changes the position of the FAB, but I cannot understand why it happens.

I want the FAB to be positioned at the bottom left. When I don't have the background set as my layer-list, it appears where I have coded.

But when I add the background attribute to the Relative layout, FAB automatically moves in.

I can't understand what is affecting this behavior of FAB.

XML for layer_list:

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

<item>
    <shape android:shape="rectangle">
        <solid android:color="@color/colorPrimary" />
        <padding
            android:bottom="64dp"
            android:left="32dp"
            android:right="32dp"
            android:top="64dp" />
    </shape>
</item>

<item>
    <shape android:shape="rectangle">
        <solid android:color="#FFFFFF" />
        <corners
            android:bottomLeftRadius="64dp"
            android:bottomRightRadius="64dp"
            android:topLeftRadius="64dp"
            android:topRightRadius="64dp" />
    </shape>
</item>

XML for Activity:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/home_layer_list">

<TextView
    android:id="@+id/text_view"
    android:layout_centerInParent="true"
    android:textSize="36sp"
    android:textStyle="bold"
    android:textColor="@color/colorPrimary"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="hello world" />

<android.support.design.widget.FloatingActionButton
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:src="@drawable/ic_fab"
    android:layout_margin="16dp"
    app:backgroundTint="#FFFFFF"/>

How can I make the FAB move back to the position where it was initially?

Try to change your layout like below:

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

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/home_layer_list">

        <TextView
            android:id="@+id/text_view"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:text="hello world"
            android:textColor="@color/colorPrimary"
            android:textSize="36sp"
            android:textStyle="bold" />
    </RelativeLayout>

    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentBottom="true"
        android:src="@drawable/ic_fab"
        android:layout_margin="16dp"
        app:backgroundTint="#FFFFFF" />

</RelativeLayout>