activity_scanner.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:id="@+id/content_frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent"></FrameLayout>

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top"
        android:background="@color/actionbar_opacity"
        android:minHeight="?attr/actionBarSize"
        app:theme="@style/TransparentToolbar" />

    <Button
        android:id="@+id/buttonNextScan"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal|bottom"
        android:layout_marginBottom="80dp"
        android:onClick="resume"
        android:text="@string/next_scan"
        android:textColor="@android:color/black"
        android:visibility="gone" />

</FrameLayout>