How to add floating action button on top of scrollview

Question

I have a floating action button that I would like to add on top of a scrollview so that the button stays, even if you scroll. I want it on the top of the scrollview and in the bottom right corner of the screen. What combination of views do I need to use to accomplish this?

Here is the xml file:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:fab="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.nhscoding.safe2tell.STORIES"
    android:background="@color/stor_back">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="bottom"
        >

        <com.getbase.floatingactionbutton.FloatingActionButton
            android:id="@+id/pink_icon"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            fab:fab_icon="@drawable/ic_add"
            fab:fab_colorNormal="@color/fab_back"
            fab:fab_colorPressed="@color/fab_pressed_back"
            android:layout_gravity="end"
            android:layout_marginBottom="16dp"
            android:layout_marginRight="16dp"/>
        </LinearLayout>


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

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



            <android.support.v7.widget.CardView
                xmlns:card_view="http://schemas.android.com/apk/res-auto"
                android:id="@+id/card_view1"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:layout_marginTop="@dimen/card_margin_top"
                android:layout_marginBottom="@dimen/card_margin_bottom"
                android:layout_marginLeft="@dimen/card_margin_left"
                android:layout_marginRight="@dimen/card_margin_right"
                card_view:cardCornerRadius="@dimen/card_radius"
                >

                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginTop="@dimen/card_title_top"
                    android:layout_marginBottom="@dimen/card_title_bottom"
                    android:layout_marginLeft="@dimen/card_title_left"
                    android:layout_marginRight="@dimen/card_title_right"
                    android:text="@string/card1_title"
                    android:textSize="@dimen/card_title_size"
                    android:gravity="top"
                    android:id="@+id/title1"
                    />


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

            <android.support.v7.widget.CardView
                xmlns:card_view="http://schemas.android.com/apk/res-auto"
                android:id="@+id/card_view2"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:layout_marginTop="@dimen/card_margin_top"
                android:layout_marginBottom="@dimen/card_margin_bottom"
                android:layout_marginLeft="@dimen/card_margin_left"
                android:layout_marginRight="@dimen/card_margin_right"
                card_view:cardCornerRadius="@dimen/card_radius"
                android:layout_below="@id/card_view1">

                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginTop="@dimen/card_title_top"
                    android:layout_marginBottom="@dimen/card_title_bottom"
                    android:layout_marginLeft="@dimen/card_title_left"
                    android:layout_marginRight="@dimen/card_title_right"
                    android:text="@string/card2_title"
                    android:textSize="@dimen/card_title_size"
                    android:gravity="top"
                    />

                <TextView
                    android:id="@+id/info_text2"
                    android:layout_marginTop="16dp"
                    android:layout_marginBottom="0dp"
                    android:layout_marginLeft="16dp"
                    android:layout_marginRight="16dp"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"/>
            </android.support.v7.widget.CardView>

            <android.support.v7.widget.CardView
                xmlns:card_view="http://schemas.android.com/apk/res-auto"
                android:id="@+id/card_view3"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:layout_marginTop="@dimen/card_margin_top"
                android:layout_marginBottom="@dimen/card_margin_bottom"
                android:layout_marginLeft="@dimen/card_margin_left"
                android:layout_marginRight="@dimen/card_margin_right"
                card_view:cardCornerRadius="@dimen/card_radius"
                android:layout_below="@id/card_view2">

                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginTop="@dimen/card_title_top"
                    android:layout_marginBottom="@dimen/card_title_bottom"
                    android:layout_marginLeft="@dimen/card_title_left"
                    android:layout_marginRight="@dimen/card_title_right"
                    android:text="@string/card3_title"
                    android:textSize="@dimen/card_title_size"
                    android:gravity="top"
                    />

                <TextView
                    android:id="@+id/info_text3"
                    android:layout_marginTop="16dp"
                    android:layout_marginBottom="0dp"
                    android:layout_marginLeft="16dp"
                    android:layout_marginRight="16dp"
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"/>
            </android.support.v7.widget.CardView>

            <android.support.v7.widget.CardView
                xmlns:card_view="http://schemas.android.com/apk/res-auto"
                android:id="@+id/card_view1"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:layout_marginTop="@dimen/card_margin_top"
                android:layout_marginBottom="@dimen/card_margin_bottom"
                android:layout_marginLeft="@dimen/card_margin_left"
                android:layout_marginRight="@dimen/card_margin_right"
                card_view:cardCornerRadius="@dimen/card_radius">

                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginTop="@dimen/card_title_top"
                    android:layout_marginBottom="@dimen/card_title_bottom"
                    android:layout_marginLeft="@dimen/card_title_left"
                    android:layout_marginRight="@dimen/card_title_right"
                    android:text="@string/card4_title"
                    android:textSize="@dimen/card_title_size"
                    android:gravity="top"
                    android:id="@+id/title4"
                    />


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

            <android.support.v7.widget.CardView
                xmlns:card_view="http://schemas.android.com/apk/res-auto"
                android:id="@+id/card_view1"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:layout_marginTop="@dimen/card_margin_top"
                android:layout_marginBottom="16dp"
                android:layout_marginLeft="@dimen/card_margin_left"
                android:layout_marginRight="@dimen/card_margin_right"
                card_view:cardCornerRadius="@dimen/card_radius">

                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginTop="@dimen/card_title_top"
                    android:layout_marginBottom="@dimen/card_title_bottom"
                    android:layout_marginLeft="@dimen/card_title_left"
                    android:layout_marginRight="@dimen/card_title_right"
                    android:text="@string/card5_title"
                    android:textSize="@dimen/card_title_size"
                    android:gravity="top"
                    android:id="@+id/title5"
                    />


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


            </LinearLayout>
        </ScrollView>




</RelativeLayout>

Answer 1

Later children in a RelativeLayout tend to float over earlier children in a RelativeLayout.

(I say "tend to" because Android 5.0's elevation stuff also plays a role, and the relationship between them is ill-defined)

So, to have a floating action button (FAB) float over a ScrollView in a RelativeLayout, make sure that the ScrollView is defined first in the XML, with the FAB after it. This will not affect the X/Y rules, but it should have the FAB appear over the ScrollView on the Z axis.

Another possibility, if you are only supporting Android 5.0+, would be to use android:elevation itself to raise the FAB.