FloatingActionButton with BottomNavigationView

1. If you stick it in a linear layout and move the bottom nav outside of the coordinator view, it will be below it on the screen.

2. You could do it this way, but I prefer using an empty fragment container which I put in the hosting activity, and then place the fragment inside of it in code.

   <android.support.design.widget.AppBarLayout
       android:id="@+id/appbar"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:paddingTop="@dimen/appbar_padding_top"
       android:theme="@style/AppTheme.AppBarOverlay">
   
       <android.support.v7.widget.Toolbar
           android:id="@+id/toolbar"
           android:layout_width="match_parent"
           android:layout_height="?attr/actionBarSize"
           android:background="?attr/colorPrimary"
           app:layout_scrollFlags="scroll|enterAlways"
          app:popupTheme="@style/AppTheme.PopupOverlay">
   
       </android.support.v7.widget.Toolbar>
   
   </android.support.design.widget.AppBarLayout>
   
   <FrameLayout
       android:id="@+id/fragment_container"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       app:layout_behavior="@string/appbar_scrolling_view_behavior">
   
   
   </FrameLayout>
   
   <android.support.design.widget.FloatingActionButton
       android:id="@+id/fab_electricity"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_gravity="bottom|right"
       app:srcCompat="@drawable/ic_add_electro"/>
   
   
   
   </android.support.design.widget.CoordinatorLayout>
   <android.support.design.widget.BottomNavigationView
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:layout_alignParentBottom="true"
       android:layout_gravity="bottom">
   
   </android.support.design.widget.BottomNavigationView>
   </LinearLayout>
   

A quick search to FloatingActionButton.Behavior tells us the following thing.

@Override
public void onAttachedToLayoutParams(@NonNull CoordinatorLayout.LayoutParams lp) {
    if (lp.dodgeInsetEdges == Gravity.NO_GRAVITY) {
        // If the developer hasn't set dodgeInsetEdges, lets set it to BOTTOM so that
        // we dodge any Snackbars
        lp.dodgeInsetEdges = Gravity.BOTTOM;
    }
}

Since BottomNavigationView also resides at the bottom of the layout. Add following element to your BottomNavigationView and CoordinatorLayout will handle the inset and dodging for you automatically.

app:layout_insetEdge="bottom"