Break the form into its own widget, since eventually it'll likely be a pop-up.

lib/main.dart

@@ -2,28 +2,42 @@
 // - https://flutter.dev/docs/cookbook/forms/validation
 
 import 'package:flutter/material.dart';
+//import 'package:provider/provider.dart';
 
 void main() {
   runApp(const MainApp());
 }
 
-class MainApp extends StatefulWidget {
+class MainApp extends StatelessWidget {
   const MainApp({super.key});
 
   @override
-  State<MainApp> createState() => _MainAppState();
+  Widget build(BuildContext context) {
+
+    return MaterialApp(
+        title: 'Recurring Expense Tracker',
+        theme: ThemeData(
+          useMaterial3: true,
+          colorScheme: ColorScheme.fromSeed(seedColor: Colors.green),
+        ),
+        home: Scaffold(
+        body: ExpenseInputForm(),
+        //floatingActionButton: IconButton(onPressed: appState.newExpense(), icon: Icon(Icons.add)),
+      ),
+    );
+  }
 }
 
-class _MainAppState extends State<MainApp> {
+class ExpenseInputForm extends StatefulWidget {
-  final nameFieldController = TextEditingController();
+  const ExpenseInputForm({
+    super.key,
+  });
 
   @override
-  void dispose() {
+  State<ExpenseInputForm> createState() => _ExpenseInputFormState();
-    // Clean up the controller when the widget is disposed.
+}
-    nameFieldController.dispose();
-    super.dispose();
-  }
 
+class _ExpenseInputFormState extends State<ExpenseInputForm> {
   @override
   Widget build(BuildContext context) {
     const inputWidth = 400.0;
@@ -37,52 +51,48 @@ class _MainAppState extends State<MainApp> {
       DropdownMenuEntry(value: Recurrence.yearly, label: "Yearly"),
     ];
 
-    return const MaterialApp(
+    return Center(
-      home: Scaffold(
+      child: Column(mainAxisSize: MainAxisSize.min, spacing: 10, children: [
-        body: Center(
+        Text('Input an expense below!'),
-          child: Column(mainAxisSize: MainAxisSize.min, spacing: 10, children: [
+        SizedBox(
-            Text('Input an expense below!'),
+            width: inputWidth,
-            SizedBox(
+            height: inputHeight,
-                width: inputWidth,
+            child: TextField(
-                height: inputHeight,
+              keyboardType: TextInputType.text,
-                child: TextField(
+              decoration: InputDecoration(
-                  keyboardType: TextInputType.text,
+                labelText: "Name",
-                  decoration: InputDecoration(
+                hintText: "Example: Red Pocket Phone Bill",
-                    labelText: "Name",
-                    hintText: "Example: Red Pocket Phone Bill",
-                  ),
-                  // https://docs.flutter.dev/cookbook/forms/retrieve-input
-                  //controller: nameFieldController,
-                )),
-            SizedBox(
-              width: inputWidth,
-              height: inputHeight,
-              child: TextField(
-                keyboardType: TextInputType.numberWithOptions(decimal: true),
-                decoration: InputDecoration(
-                    labelText: "Cost", hintText: "Example: 10.00"),
               ),
-            ),
+              // https://docs.flutter.dev/cookbook/forms/retrieve-input
-            DropdownMenu(
+              //controller: nameFieldController,
-              dropdownMenuEntries: recurrenceValues,
+            )),
-              width: inputWidth,
+        SizedBox(
-              label: Text("Recurrence"),
+          width: inputWidth,
-              hintText: "Example: Monthly",
+          height: inputHeight,
-            ),
+          child: TextField(
-            SizedBox(
+            keyboardType: TextInputType.numberWithOptions(decimal: true),
-                width: inputWidth,
+            decoration: InputDecoration(
-                height: inputHeight,
+                labelText: "Cost", hintText: "Example: 10.00"),
-                child: TextField(
+          ),
-                  keyboardType: TextInputType.text,
-                  decoration: InputDecoration(
-                      labelText: "Description",
-                      hintText:
-                          "Example: 1GB data with unlimited talk & text."
-                    ),
-                )),
-          ]),
         ),
-      ),
+        DropdownMenu(
+          dropdownMenuEntries: recurrenceValues,
+          width: inputWidth,
+          label: Text("Recurrence"),
+          hintText: "Example: Monthly",
+        ),
+        SizedBox(
+            width: inputWidth,
+            height: inputHeight,
+            child: TextField(
+              keyboardType: TextInputType.text,
+              decoration: InputDecoration(
+                  labelText: "Description",
+                  hintText:
+                      "Example: 1GB data with unlimited talk & text."
+                ),
+            )),
+      ]),
     );
   }
 }