Overlay Floating Button in Linear Layout

I have a layout like this:

But as you can see, the Floating Button is not overlaying the edit text. Is there any way to do this in Linear Layout? (I cannot use other layouts).

I have seen many answer on SO but all of them use either Relative Layout or Frame Layout.

Here is my xml (the floating button is at the end) -

<LinearLayout xmlns:android="http://ift.tt/nIICcg"
    xmlns:tools="http://ift.tt/LrGmb4"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:weightSum="10"
    android:orientation="vertical"
    tools:context=".Start">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1">

        <Button
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:text="New Button"
            android:id="@+id/button" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1">

        <Button
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:text="New Button"
            android:id="@+id/button2" />

    </LinearLayout>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="4"
        android:layout_gravity="center_horizontal"
        android:id="@+id/editText" />

    <EditText
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="4"
        android:layout_gravity="center_horizontal"
        android:id="@+id/editText2" />

    <!--Overlay this image -->

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/imageView"
        android:src="@drawable/ic_mic"
        android:layout_gravity="right" />

</LinearLayout>

Here is how I want it to look -