Make a 'refreshable_state' class which makes API requests easier

lib/widget/refreshable_state.dart

@@ -0,0 +1,61 @@
+import 'package:InvenTree/widget/drawer.dart';
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
+
+import 'package:InvenTree/widget/drawer.dart';
+
+
+abstract class RefreshableState<T extends StatefulWidget> extends State<T> {
+
+  // Storage for context once "Build" is called
+  BuildContext context;
+
+  String app_bar_title = "App Bar Title";
+
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance.addPostFrameCallback((_) => request(context));
+  }
+
+  // Function to request data for this page
+  Future<void> request(BuildContext context) async {
+    return;
+  }
+
+  Future<void> refresh() async {
+    await request(context);
+    setState(() {});
+  }
+
+  // Function to construct an appbar (override if needed)
+  AppBar getAppBar(BuildContext context) {
+    return AppBar(
+      title: Text(app_bar_title)
+    );
+  }
+
+  // Function to construct a drawer (override if needed)
+  Widget getDrawer(BuildContext context) {
+    return InvenTreeDrawer(context);
+  }
+
+  // Function to construct a body (MUST BE PROVIDED)
+  Widget getBody(BuildContext context);
+
+  @override
+  Widget build(BuildContext context) {
+
+    // Save the context for future use
+    this.context = context;
+
+    return Scaffold(
+      appBar: getAppBar(context),
+      drawer: getDrawer(context),
+      body: RefreshIndicator(
+        onRefresh: refresh,
+        child: getBody(context)
+      )
+    );
+  }
+}