Can I use a FloatingActionButton "on top" of my layout? So that it is overlapping all forms?

Question

I have the .xml style code which has a scrollview with several edittext, I need a floating button that occupies the entire screen during the entire scroll of the screen, but I did not find ways to insert it in my .xml, I tried to use coordinator layout, but the button was not displayed in the preview

Code of .xml style screen:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    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="wrap_content"
    android:background="#FAFAFA"
    android:layout_weight="1"
    android:orientation="vertical">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">
    <com.google.android.material.appbar.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar4"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:titleTextColor="@android:color/white"
            android:background="@color/colorPrimary" />
    </com.google.android.material.appbar.AppBarLayout>
    </LinearLayout>
    <com.google.android.material.textview.MaterialTextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Adicione até 3 fotos do seu produto"
        android:fontFamily="@font/bevan"
        android:gravity="center"/>

    <HorizontalScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal">
        <com.google.android.material.card.MaterialCardView
            android:layout_width="120dp"
            android:layout_height="120dp"
            android:layout_margin="6dp">
            <com.google.android.material.button.MaterialButton
                android:id="@+id/anunFoto1"
                android:layout_width="40dp"
                android:layout_height="40dp"
                android:layout_gravity="center"
                android:insetLeft="0dp"
                android:insetTop="0dp"
                android:insetRight="0dp"
                android:insetBottom="0dp"
                android:backgroundTint="@android:color/black"
                app:icon="@drawable/ic_add"
                app:iconGravity="textStart"
                app:iconPadding="0dp" />
            <ImageView
                android:id="@+id/anuncioImg1"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:visibility="gone"/>
        </com.google.android.material.card.MaterialCardView>
        <com.google.android.material.card.MaterialCardView
            android:layout_width="120dp"
            android:layout_height="120dp"
            android:layout_margin="6dp">
            <com.google.android.material.button.MaterialButton
                android:id="@+id/anunFoto2"
                android:layout_width="40dp"
                android:layout_height="40dp"
                android:layout_gravity="center"
                android:insetLeft="0dp"
                android:insetTop="0dp"
                android:insetRight="0dp"
                android:insetBottom="0dp"
                android:backgroundTint="@android:color/black"
                app:icon="@drawable/ic_add"
                app:iconGravity="textStart"
                app:iconPadding="0dp" />
            <ImageView
                android:id="@+id/anuncioImg2"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:visibility="gone"/>
        </com.google.android.material.card.MaterialCardView>
        <com.google.android.material.card.MaterialCardView
            android:layout_width="120dp"
            android:layout_height="120dp"
            android:layout_margin="6dp">
            <com.google.android.material.button.MaterialButton
                android:id="@+id/anunFoto3"
                android:layout_width="40dp"
                android:layout_height="40dp"
                android:layout_gravity="center"
                android:insetLeft="0dp"
                android:insetTop="0dp"
                android:insetRight="0dp"
                android:insetBottom="0dp"
                android:backgroundTint="@android:color/black"
                app:icon="@drawable/ic_add"
                app:iconGravity="textStart"
                app:iconPadding="0dp" />
            <ImageView
                android:id="@+id/anuncioImg3"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:visibility="gone"/>
        </com.google.android.material.card.MaterialCardView>
        </LinearLayout>
    </HorizontalScrollView>
    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">
        <com.google.android.material.textview.MaterialTextView
            android:id="@+id/alterarProvisorio"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="4dp"
            android:text="Título do Anúncio:"
            android:textAppearance="@style/TextAppearance.AppCompat.Light.SearchResult.Title" />
    <com.google.android.material.textfield.TextInputLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Ex: Gado Nelore 300Kg"
        app:startIconDrawable="@drawable/ic_text_fields_24dp"
        app:startIconTint="@color/colorPrimary"
        app:helperTextEnabled="true"
        app:helperTextTextColor="@android:color/black"
        app:helperTextTextAppearance="@style/TextAppearance.AppCompat.Caption"
        app:boxBackgroundColor="@android:color/white"
        app:counterEnabled="true"
        app:counterMaxLength="30"
        app:counterTextColor="@color/colorPrimary">
        <com.google.android.material.textfield.TextInputEditText
            android:id="@+id/tituloAnuncio"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:inputType="textShortMessage"
            android:maxLength="30" />
    </com.google.android.material.textfield.TextInputLayout>
            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content">
                <com.google.android.material.floatingactionbutton.FloatingActionButton
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"/>
            </LinearLayout>
        <com.google.android.material.textview.MaterialTextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="4dp"
            android:text="Descrição:"
            android:textAppearance="@style/TextAppearance.AppCompat.Light.SearchResult.Title" />
        <com.google.android.material.textfield.TextInputLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Ex: Gado 20 meses de vida, 10 arrobas..."
            app:startIconDrawable="@drawable/ic_short_text_24dp"
            app:startIconTint="@color/colorPrimary"
            app:helperTextEnabled="true"
            app:helperTextTextColor="@android:color/black"
            app:helperTextTextAppearance="@style/TextAppearance.AppCompat.Caption"
            app:boxBackgroundColor="@android:color/white"
            app:counterEnabled="true"
            app:counterMaxLength="240"
            app:counterTextColor="@color/colorPrimary">
            <com.google.android.material.textfield.TextInputEditText
                android:id="@+id/editDescAnuncio"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:inputType="textMultiLine"
                android:maxLength="240"/>
        </com.google.android.material.textfield.TextInputLayout>
        <com.google.android.material.textview.MaterialTextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="4dp"
            android:text="Preço inicial:"
            android:textAppearance="@style/TextAppearance.AppCompat.Light.SearchResult.Title" />
        <com.google.android.material.textfield.TextInputLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Ex: 1650"
            app:startIconDrawable="@drawable/ic_monetization_on"
            app:startIconTint="@color/colorPrimary"
            app:helperTextEnabled="true"
            app:helperTextTextColor="@android:color/black"
            app:helperTextTextAppearance="@style/TextAppearance.AppCompat.Caption"
            app:boxBackgroundColor="@android:color/white"
            app:counterEnabled="true"
            app:counterMaxLength="6"
            app:counterTextColor="@color/colorPrimary">
            <com.google.android.material.textfield.TextInputEditText
                android:id="@+id/editPrecoAnuncio"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:inputType="numberSigned"
                android:maxLength="6" />
        </com.google.android.material.textfield.TextInputLayout>
            <com.google.android.material.textview.MaterialTextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginStart="4dp"
                android:text="Classificação do Bovino:"
                android:textAppearance="@style/TextAppearance.AppCompat.Light.SearchResult.Title" />
            <com.google.android.material.button.MaterialButton
                android:id="@+id/classBovinos"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Escolha até 3 classes do seu bovino"
                android:drawableLeft="@drawable/ic_class_white_24dp"
                android:drawableTint="@color/colorPrimary"
                android:textColor="@android:color/black"
                android:backgroundTint="@android:color/white"/>
            <com.google.android.material.textview.MaterialTextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginStart="4dp"
                android:text="Cidade do Anunciante:"
                android:textAppearance="@style/TextAppearance.AppCompat.Light.SearchResult.Title" />
            <com.google.android.material.textfield.TextInputLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:hint="Ex: Goiânia"
                app:startIconDrawable="@drawable/ic_location_on_24dp"
                app:startIconTint="@color/colorPrimary"
                app:helperTextEnabled="true"
                app:helperTextTextColor="@android:color/black"
                app:helperTextTextAppearance="@style/TextAppearance.AppCompat.Caption"
                app:boxBackgroundColor="@android:color/white"
                app:counterEnabled="true"
                app:counterTextColor="@color/colorPrimary">
                <com.google.android.material.textfield.TextInputEditText
                    android:id="@+id/editCidade"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:inputType="textCapWords" />
            </com.google.android.material.textfield.TextInputLayout>
            <com.google.android.material.textview.MaterialTextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginStart="4dp"
                android:text="Estado do anunciante:"
                android:textAppearance="@style/TextAppearance.AppCompat.Light.SearchResult.Title" />
            <com.google.android.material.textfield.TextInputLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:hint="Ex: Goiás"
                app:startIconDrawable="@drawable/ic_location_on_24dp"
                app:startIconTint="@color/colorPrimary"
                app:helperTextEnabled="true"
                app:helperTextTextColor="@android:color/black"
                app:helperTextTextAppearance="@style/TextAppearance.AppCompat.Caption"
                app:boxBackgroundColor="@android:color/white"
                app:counterTextColor="@color/colorPrimary">
                <com.google.android.material.textfield.TextInputEditText
                    android:id="@+id/editEstado"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:inputType="textCapWords" />
            </com.google.android.material.textfield.TextInputLayout>
            <com.google.android.material.textview.MaterialTextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginStart="4dp"
                android:text="Data Anúncio:"
                android:textAppearance="@style/TextAppearance.AppCompat.Light.SearchResult.Title" />
            <com.google.android.material.textfield.TextInputLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:hint="Ex: 19/05/2020"
                app:startIconDrawable="@drawable/ic_date_range_24dp"
                app:startIconTint="@color/colorPrimary"
                app:helperTextEnabled="true"
                app:helperTextTextColor="@android:color/black"
                app:helperTextTextAppearance="@style/TextAppearance.AppCompat.Caption"
                app:boxBackgroundColor="@android:color/white"
                app:counterTextColor="@color/colorPrimary">
                <com.google.android.material.textfield.TextInputEditText
                    android:id="@+id/editData"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:inputType="date" />
            </com.google.android.material.textfield.TextInputLayout>
        </LinearLayout>
    </ScrollView>
</LinearLayout>

I need that the button keep here:

.xml of FloatingAction with CoordinatorLayout that i tried previously:

 <androidx.coordinatorlayout.widget.CoordinatorLayout
        android:id="@+id/coordinator2"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="1.0">

        <com.google.android.material.floatingactionbutton.FloatingActionButton
            android:id="@+id/buttonFloatingAdicionar"
            style="@style/Widget.MaterialComponents.FloatingActionButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|end"
            android:layout_margin="16dp"
            android:backgroundTint="@color/amarelo2"
            app:backgroundTint="@color/amarelo2"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@id/linearLayout2"
            app:maxImageSize="56dp"
            app:rippleColor="@color/amarelo2"
            app:srcCompat="@drawable/ic_add" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>

Update 1 Currently i'm using this solution, not is appropriate, but, resolve.

.xml

<LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:gravity="end"
        android:layout_below="@id/first2">
        <com.google.android.material.floatingactionbutton.FloatingActionButton
            android:id="@+id/salvarAnuncio"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:backgroundTint="@color/azul4"
            android:src="@drawable/ic_publish_24dp"
            app:tint="@android:color/white"
            app:borderWidth="0dp"
            app:fabSize="normal"
            android:layout_gravity="bottom"
            android:tooltipText="Salvar" />
    </LinearLayout>

Answer 1

You could switch the outermost layout to RelativeLayout and position the button appropriately. But a quick fix could be to wrap the whole XML inside a <RelativeLayout> and shift the floating action button.

<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="wrap_content"
    android:background="#FAFAFA">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="#FAFAFA"
    android:layout_weight="1"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <com.google.android.material.appbar.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
...
...
...
 </ScrollView>
</LinearLayout>
    <LinearLayout
        android:layout_centerInParent="true"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <com.google.android.material.floatingactionbutton.FloatingActionButton
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </LinearLayout>
</RelativeLayout>