title: How to align Floating Action Button to center
body: <p>I have one FloatingActionButton. I want it to be middle of 2 LinearLayouts and center of screen like this.  <a href="https://i.stack.imgur.com/TKFgU.jpg"><img src="https://i.stack.imgur.com/TKFgU.jpg" alt="enter image description here"></a></p>
  
  <p>Currently My design is like this </p>
  
  <p><a href="https://i.stack.imgur.com/uoMAx.png"><img src="https://i.stack.imgur.com/uoMAx.png" alt="enter image description here"></a></p>
  
  <p>I want it to be at the exact center of the screen. How to do that?</p>
  
  <p>This is my whole xml code</p>
  
  <pre><code>&lt;android.support.design.widget.CoordinatorLayout
  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"&gt;
  &lt;LinearLayout android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:orientation="vertical"&gt;
      &lt;LinearLayout
          android:id="@+id/viewA"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_weight="1.6"
          android:orientation="horizontal"/&gt;
      &lt;LinearLayout
          android:id="@+id/viewB"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_weight="0.2"
          android:orientation="horizontal"/&gt;
  &lt;/LinearLayout&gt;
  &lt;android.support.design.widget.FloatingActionButton
      android:id="@+id/fab"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:clickable="true"
      android:src="@drawable/ic_plus"
      app:layout_anchor="@id/viewA"
      android:layout_centerHorizontal="true"
      app:layout_anchorGravity="bottom"
      android:layout_centerInParent="true" /&gt;
  </code></pre>
  
  <p></p>