part category display is now refreshable

lib/widget/category_display.dart

@@ -5,6 +5,7 @@ import 'package:InvenTree/preferences.dart';
 
 import 'package:InvenTree/widget/part_detail.dart';
 import 'package:InvenTree/widget/drawer.dart';
+import 'package:InvenTree/widget/refreshable_state.dart';
 
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
@@ -26,11 +27,12 @@ class CategoryDisplayWidget extends StatefulWidget {
 }
 
 
-class _CategoryDisplayState extends State<CategoryDisplayWidget> {
+class _CategoryDisplayState extends RefreshableState<CategoryDisplayWidget> {
 
-  _CategoryDisplayState(this.category) {
-    _requestData();
-  }
+  @override
+  String app_bar_title = "Part Category";
+
+  _CategoryDisplayState(this.category) {}
 
   // The local InvenTreePartCategory object
   final InvenTreePartCategory category;
@@ -39,19 +41,11 @@ class _CategoryDisplayState extends State<CategoryDisplayWidget> {
 
   List<InvenTreePart> _parts = List<InvenTreePart>();
 
-  String get _titleString {
-
-    if (category == null) {
-      return "Part Categories";
-    } else {
-      return "Part Category - ${category.name}";
-    }
-  }
-
   /*
    * Request data from the server
    */
-  void _requestData() {
+  @override
+  Future<void> request(BuildContext context) async {
 
     int pk = category?.pk ?? -1;
 
@@ -127,13 +121,8 @@ class _CategoryDisplayState extends State<CategoryDisplayWidget> {
   }
 
   @override
-  Widget build(BuildContext context) {
-    return Scaffold(
-      appBar: AppBar(
-        title: Text(_titleString),
-      ),
-      drawer: new InvenTreeDrawer(context),
-      body: ListView(
+  Widget getBody(BuildContext context) {
+    return ListView(
       children: <Widget>[
         getCategoryDescriptionCard(),
         ExpansionPanelList(
@@ -194,7 +183,6 @@ class _CategoryDisplayState extends State<CategoryDisplayWidget> {
           ],
         ),
       ]
-        )
     );
   }
 }