您可以使用 CoordinatorLayout 开始布局，然后可以将FAB锚定( layout_anchor )您的 ScrollView 并应用布局重力( layout_anchorGravity )将其放置在右下角( bottom | end ):

You can start the layout with a CoordinatorLayout and then you can anchor (layout_anchor) your FAB to your ScrollView and apply a layout gravity (layout_anchorGravity) to place it bottom-right (bottom|end):

<android.support.design.widget.FloatingActionButton
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_margin="@dimen/fab_margin"
    app:layout_anchorGravity="bottom|end"
    app:layout_anchor="@id/scrollView1"
    app:srcCompat="@drawable/ic_info_2x" />

类似的东西:

<?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" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">
    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >
            <ImageView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/imageView1" />
            <View
                android:layout_width="match_parent"
                android:layout_height="2dp"
                android:layout_gravity="center"
                android:layout_marginTop="0sp"
                android:background="#000000" />
            <TextView
                android:text="New Account"
                android:textAppearance="?android:attr/textAppearanceLarge"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/textView1"
                android:textAlignment="center" />
        </LinearLayout>
        <ScrollView
            android:id="@+id/scrollView1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="vertical" >
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:text="Enter Username"
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="150.5dp"
                        android:layout_height="wrap_content"
                        android:id="@+id/textView1"/>
                    <EditText
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:id="@+id/aTextboxUsername" />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:text="Enter Password"
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="150.5dp"
                        android:layout_height="wrap_content"
                        android:id="@+id/textView1"/>
                    <EditText
                        android:inputType="textPassword"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:id="@+id/aTextboxPassword"
                        android:autoLink="none" />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:text="Confirm Password"
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="150.5dp"
                        android:layout_height="wrap_content"
                        android:id="@+id/textView1"/>
                    <EditText
                        android:inputType="textPassword"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:id="@+id/aTextboxPassword2"
                        android:autoLink="none" />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:text="Enter Email Address"
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="192.5dp"
                        android:layout_height="wrap_content"
                        android:id="@+id/textView1"/>
                    <EditText
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:id="@+id/txtEmailAddress"
                        android:autoLink="none" />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:text="Confirm Email Address"
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="193.5dp"
                        android:layout_height="wrap_content"
                        android:id="@+id/textView1"/>
                    <EditText
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:id="@+id/txtEmailAddress2"
                        android:autoLink="none" />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="130dp"
                        android:layout_height="wrap_content"
                        android:text="First Name" />
                    <EditText
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:id="@+id/motherfirstname"
                         />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="130dp"
                        android:layout_height="wrap_content"
                        android:text="Middle Initial" />
                    <EditText
                        android:layout_width="50dp"
                        android:layout_height="wrap_content"
                        android:maxLength = "1"
                        android:id="@+id/mothermi"/>
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="130dp"
                        android:layout_height="wrap_content"
                        android:text="Last Name" />
                    <EditText
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:id="@+id/motherlastname"/>
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="130dp"
                        android:layout_height="35dp"
                        android:text="Suffix" />
                    <Spinner
                        android:layout_width="110dp"
                        android:layout_height="35dp"
                        android:id="@+id/spinner_suffix" />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="130dp"
                        android:layout_height="wrap_content"
                        android:text="Address" />
                    <EditText
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:id="@+id/motheraddress"
                         />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="130dp"
                        android:layout_height="wrap_content"
                        android:text="City" />
                    <EditText
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:id="@+id/mothercity"
                         />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="130dp"
                        android:layout_height="wrap_content"
                        android:text="State" />
                    <Spinner
                        android:layout_width="110dp"
                        android:layout_height="35dp"
                        android:id="@+id/motherstate" />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">
                    <TextView
                        android:textAppearance="?android:attr/textAppearanceMedium"
                        android:layout_width="130dp"
                        android:layout_height="wrap_content"
                        android:text="Zip Code" />
                    <EditText
                        android:layout_width="50dp"
                        android:layout_height="wrap_content"
                        android:maxLength = "5"
                        android:id="@+id/motherzip"/>
                </LinearLayout>
                <View
                    android:layout_width="match_parent"
                    android:layout_height="2dp"
                    android:layout_gravity="center"
                    android:layout_marginTop="0sp"
                    android:background="#000000" />
                <TextView
                    android:textAppearance="?android:attr/textAppearanceMedium"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAlignment="center"
                    android:text="Select League, Program, Team you are" />
                <View
                    android:layout_width="match_parent"
                    android:layout_height="2dp"
                    android:layout_gravity="center"
                    android:layout_marginTop="0sp"
                    android:background="#000000" />
                <TextView
                    android:text="Select League"
                    android:textAppearance="?android:attr/textAppearanceMedium"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAlignment="center" 
                    android:textStyle="bold"
                    android:id="@+id/textView2" />
                <Spinner
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAlignment="center"
                    android:id="@+id/league_spinner" />
                <TextView
                    android:text="Select Program"
                    android:textAppearance="?android:attr/textAppearanceMedium"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAlignment="center" 
                    android:textStyle="bold"
                    android:id="@+id/textView2" />
                <Spinner
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAlignment="center"
                    android:id="@+id/program_spinner" />

                    <TextView
                    android:text="Select Team"
                    android:textAppearance="?android:attr/textAppearanceMedium"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAlignment="center" 
                    android:textStyle="bold"
                    android:id="@+id/textView2" />
                <Spinner
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAlignment="center"
                    android:id="@+id/team_spinner" />
                <Button
                    android:text="Submit"
                    android:layout_width="200px"
                    android:layout_gravity="center"
                    android:layout_height="34.5dp"
                    android:id="@+id/button_submit" />
            </LinearLayout>
        </ScrollView>
    </LinearLayout>
    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_margin="@dimen/fab_margin"
        app:layout_anchorGravity="bottom|end"
        app:layout_anchor="@id/scrollView1"
        app:srcCompat="@android:drawable/ic_dialog_email" />
</android.support.design.widget.CoordinatorLayout>