How to align linearlayout to vertical center?

I'm trying to align LinearLayout's vertical center which shows following pic (skycolor border) to delete button's vertical center.

so I set the gravity of id:groupNumbers to center_vertical.

but no changed.

How to align id:groupNumbers to button's center?

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="horizontal"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

    <LinearLayout
            android:id="@+id/groupNumbers"
            android:orientation="horizontal"
            android:gravity="center_vertical"
            android:layout_weight="0.7"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content">

        <LinearLayout
                android:orientation="horizontal"
                android:layout_weight="1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content">

            <TextView
                    android:id="@+id/txtSelected01"
                    android:text="00"
                    android:textSize="30dp"
                    android:gravity="center_horizontal"
                    android:layout_weight="1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"/>
        </LinearLayout>

        <LinearLayout
                android:orientation="horizontal"
                android:layout_weight="1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content">

            <TextView
                    android:id="@+id/txtSelected02"
                    android:text="00"
                    android:textSize="30dp"
                    android:gravity="center_horizontal"
                    android:layout_weight="1"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"/>
        </LinearLayout>
    </LinearLayout>


    <Button
            android:id="@+id/btn_deleteNum"
            android:text="Delete"
            android:textSize="20dp"
            android:layout_weight="0.2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
</LinearLayout>

Change orientation and gravity in

<LinearLayout
    android:id="@+id/groupNumbers"
    android:orientation="horizontal"
    android:gravity="center_vertical"
    android:layout_weight="0.7"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

to

android:orientation="vertical"
android:layout_gravity="center_vertical"

You are adding orientation: horizontal, so the layout will contain all elements in single horizontal line. Which won't allow you to get the element in center.