I hope that this is what you want. I'm not sure if I understand you correctly, though.
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- SurfaceView should cover all the screens width -->
<SurfaceView
android:id="@+id/surfaceViewBarcodeScanner"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
<!-- TextView should be above SurfaceView -->
<TextView
android:id="@+id/mytext"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/mbackground2"
android:gravity="center_horizontal"
android:padding="20dip"
android:textColor="@color/mytextcolor"/>
<!-- LinearLayout will contain linear toolbar -->
<LinearLayout
android:id="@+id/ScannerBottomToolbar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:layout_marginBottom="48dp"
android:layout_marginLeft="77dp"
android:orientation="vertical">
</LinearLayout>
</FrameLayout>