Basic layout

lib/flutter_address_form.dart

@@ -1,7 +1,3 @@
 library flutter_address_form;
 
-/// A Calculator.
+export 'src/address_form.dart';
-class Calculator {
-  /// Returns [value] plus 1.
-  int addOne(int value) => value + 1;
-}

lib/src/address_form.dart

@@ -0,0 +1,67 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
+
+class AddressForm extends StatefulWidget {
+  AddressForm({Key? key}) : super(key: key);
+
+  @override
+  State<AddressForm> createState() => _AddressFormState();
+}
+
+class _AddressFormState extends State<AddressForm> {
+  final TextEditingController _zipcodeController = TextEditingController();
+  final RegExp _zipcodeRegExp = RegExp(r'^[1-9][0-9]{3}\s?[a-zA-Z]{2}$');
+  @override
+  Widget build(BuildContext context) {
+    return Form(
+      child: Column(
+        children: [
+          _createField(
+            label: 'Postcode',
+            controller: _zipcodeController,
+          ),
+          Flexible(
+            child: Row(
+              children: [
+                _createField(
+                  label: 'Huisnummer',
+                  controller: TextEditingController(),
+                ),
+                _createField(
+                  label: 'Toevoeging',
+                  controller: TextEditingController(),
+                ),
+              ],
+            ),
+          ),
+          _createField(
+            label: 'Straatnaam',
+            controller: TextEditingController(),
+          ),
+          _createField(
+            label: 'Woonplaats',
+            controller: TextEditingController(),
+          )
+        ],
+      ),
+    );
+  }
+
+  Widget _createField(
+      {required String label, required TextEditingController controller}) {
+    return Flexible(
+      child: Container(
+        margin: const EdgeInsets.all(10),
+        child: TextFormField(
+          validator: (value) {
+            print(_zipcodeRegExp.hasMatch(value!));
+          },
+          decoration: InputDecoration(
+            label: Text(label),
+            border: const OutlineInputBorder(),
+          ),
+        ),
+      ),
+    );
+  }
+}