Java – float action button layout anchor does not work

I want to have a float action button between my two related layouts.

To do this, I set the parent layout as the coordinator layout and assigned anchor and anchor gravity to the fab button.

But it wasn’t set to where I wanted.

I want it to be set between relative layout6 in the upper right corner and between relative layout6 and relative layout3 in the upper right corner.

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/bg"
    android:orientation="vertical">

<ScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fillViewport="true">

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

<RelativeLayout
                android:id="@+id/relativeLayoutParent"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_above="@+id/imageView5"
                android:layout_alignParentLeft="true"
                android:layout_alignParentStart="true"
                android:layout_alignParentTop="true"
                android:layout_marginEnd="30dp"
                android:layout_marginLeft="30dp"
                android:layout_marginRight="30dp"
                android:layout_marginStart="30dp"
                android:layout_marginTop="30dp"
                android:background="@color/colorAccent">

<RelativeLayout
                    android:id="@+id/relativeLayout6"
                    android:layout_width="match_parent"
                    android:layout_height="240dp"
                    android:layout_centerHorizontal="true">

<ImageView
                        android:id="@+id/imageView7"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_alignParentLeft="true"
                        android:layout_alignParentStart="true"
                        android:layout_alignParentTop="true"
                        android:scaleType="fitXY"
                        app:srcCompat="@drawable/profile_img" />

</LinearLayout>

</RelativeLayout>

<RelativeLayout
                    android:id="@+id/relativeLayout3"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignParentEnd="true"
                    android:layout_alignParentLeft="true"
                    android:layout_alignParentRight="true"
                    android:layout_alignParentStart="true"
                    android:layout_below="@+id/relativeLayout6">

</RelativeLayout>

<android.support.design.widget.FloatingActionButton
                android:id="@+id/fab"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                app:layout_anchorGravity="center"
                app:layout_anchor = "@id/linearLayout"
                android:layout_margin="@dimen/fab_margin"
                app:srcCompat="@android:drawable/ic_dialog_email" />
        </LinearLayout>

</ScrollView>

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

Please help: Thank you.

Put the FloatingActionButton in CoordinatorLayout. The anchor property is only valid in CoordinatorLayout.
One more thing: your layout is messy. Please arrange.

<?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:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/bg"
android:orientation="vertical">

<ScrollView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:fillViewport="true">

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

<RelativeLayout
            android:id="@+id/relativeLayoutParent"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_above="@+id/imageView5"
            android:layout_alignParentLeft="true"
            android:layout_alignParentStart="true"
            android:layout_alignParentTop="true"
            android:layout_marginEnd="30dp"
            android:layout_marginLeft="30dp"
            android:layout_marginRight="30dp"
            android:layout_marginStart="30dp"
            android:layout_marginTop="30dp"
            android:background="@color/colorAccent" />

<RelativeLayout
            android:id="@+id/relativeLayout6"
            android:layout_width="match_parent"
            android:layout_height="240dp"
            android:layout_centerHorizontal="true" />

<ImageView
            android:id="@+id/imageView7"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_alignParentStart="true"
            android:layout_alignParentTop="true"
            android:scaleType="fitXY"
            app:srcCompat="@drawable/profile_img" />

</LinearLayout>

<RelativeLayout
        android:id="@+id/relativeLayout3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/relativeLayout6" />
</ScrollView>

<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="@dimen/fab_margin"
    app:layout_anchor="@id/linearLayout"
    app:layout_anchorGravity="center"
    app:srcCompat="@android:drawable/ic_dialog_email" />