How to center image in FloatingActionButton behind transparent background?

Question

I have a FloatingActionButton and I would like to make it transparent with a centered icon.

I added a style:

<style name="ButtonTransparent">
    <item name="colorAccent">@android:color/transparent</item>
</style>

which works so far. THe FAB got transparent. Then I added the FAB :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".activities.CameraActivity">
    <TextureView
        android:id="@+id/texture"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"/>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true">

        <ImageView
            android:id="@+id/iv_last_image"
            android:layout_width="60dp"
            android:layout_height="60dp"
            android:layout_gravity="center_horizontal"
            android:layout_margin="10dp" />

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/btn_takepicture"
            android:layout_width="80dp"
            android:layout_height="80dp"
            android:layout_gravity="center_horizontal"
            android:layout_margin="20dp"
            android:theme="@style/ButtonTransparent"
            android:src="@drawable/selector_vector_camera_light" />

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/btn_back"
            android:layout_width="60dp"
            android:layout_height="60dp"
            android:layout_gravity="center_horizontal"
            android:layout_margin="20dp"
            android:theme="@style/ButtonTransparent"
            android:src="@drawable/selector_vector_go_back" />
    </LinearLayout>
</RelativeLayout>

but as you can see on the screenshot below it is not well aligned. How can I correct that?

Answer 1

Image is positioned properly but the shadow in background no. If you press the button then it is even worse.

To minimaze this effect you can change elevation and pressedTranslationZ

      app:elevation="1dp"
      app:borderWidth="0dp"
      app:pressedTranslationZ="1dp"

And you will get: