Android: How to disable scanning in transparent area

Question

I'm using google.zxing.code library for scanning QR codes. I'm having PreviewView in full screen and I'm trying to make it working in only center part and other part should be transparent as attached screenshot. But its scanning successfully in top and bottom transparent area.

I need this are just transparent and scanner should not load result if QR code comes in this area. I'm using below snippet for this.

<androidx.camera.view.PreviewView
    android:id="@+id/preview_view"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:background="#CC000000"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    tools:visibility="visible" />

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:background="#CC000000" />

    <LinearLayout
        android:id="@+id/camera_view"
        android:layout_width="fill_parent"
        android:layout_height="350dp"
        android:orientation="horizontal">

        <RelativeLayout
            android:layout_width="0dp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:background="#CC000000" />

        <RelativeLayout
            android:id="@+id/rlscan"
            android:layout_width="280dp"
            android:layout_height="fill_parent">
        </RelativeLayout>

        <RelativeLayout
            android:layout_width="0dp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:background="#CC000000" />
    </LinearLayout>

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:background="#CC000000">

        <TextView
            android:id="@+id/txtResult"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:layout_marginTop="20dp"
            android:gravity="center_horizontal"
            android:text="Please focus Camera to QR Code"
            android:textSize="10sp" />
    </RelativeLayout>
</LinearLayout>

Please help me if someone knows the approach. Thanks in advance.