How to align linearlayout to vertical center?

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.