XML : add Toolbar to Google Map

I am new in app development and I am having difficult in putting a tool bar above the google map.

I followed online indication, but when I lunch the code I cannot see the toolbar.

  <FrameLayout  xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:map="http://schemas.android.com/apk/res-auto"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="vertical">    <android.support.v7.widget.Toolbar      xmlns:sothree="http://schemas.android.com/apk/res-auto"      xmlns:android="http://schemas.android.com/apk/res/android"      android:id="@+id/app_bar"      android:layout="@layout/toolbar"      android:layout_height="match_parent"      android:layout_width="match_parent"/>    <fragment  xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:map="http://schemas.android.com/apk/res-auto"  xmlns:tools="http://schemas.android.com/tools"  android:id="@+id/map"      android:layout_below="@+id/app_bar"  android:name="com.google.android.gms.maps.SupportMapFragment"  android:layout_width="match_parent"  android:layout_height="match_parent"  tools:context="com.example.namexxx.app.homemap"  />    </FrameLayout>    

What Am I doing wrong?