Update title in app bar

app/src/main/res/navigation/nav_graph.xml

@@ -21,7 +21,7 @@
     <fragment
         android:id="@+id/startFragment"
         android:name="com.example.cupcake.StartFragment"
-        android:label="fragment_start"
+        android:label="@string/app_name"
         tools:layout="@layout/fragment_start" >
         <action
             android:id="@+id/action_startFragment_to_flavorFragment"
@@ -30,7 +30,7 @@
     <fragment
         android:id="@+id/flavorFragment"
         android:name="com.example.cupcake.FlavorFragment"
-        android:label="fragment_flavor"
+        android:label="@string/choose_flavor"
         tools:layout="@layout/fragment_flavor" >
         <action
             android:id="@+id/action_flavorFragment_to_pickupFragment"
@@ -39,7 +39,7 @@
     <fragment
         android:id="@+id/pickupFragment"
         android:name="com.example.cupcake.PickupFragment"
-        android:label="fragment_pickup"
+        android:label="@string/choose_pickup_date"
         tools:layout="@layout/fragment_pickup" >
         <action
             android:id="@+id/action_pickupFragment_to_summaryFragment"
@@ -48,6 +48,6 @@
     <fragment
         android:id="@+id/summaryFragment"
         android:name="com.example.cupcake.SummaryFragment"
-        android:label="fragment_summary"
+        android:label="@string/order_summary"
         tools:layout="@layout/fragment_summary" />
 </navigation>
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