feat: add auth drop down field

lib/flutter_registration.dart

@@ -11,6 +11,7 @@ export 'src/model/auth_field.dart';
 export 'src/model/auth_step.dart';
 export 'src/model/auth_text_field.dart';
 export 'src/model/auth_bool_field.dart';
+export 'src/model/auth_drop_down.dart';
 export 'src/registration_screen.dart';
 export 'src/service/registration_repository.dart';
 export 'package:flutter_input_library/flutter_input_library.dart'

lib/src/auth_screen.dart

@@ -149,17 +149,11 @@ class _AuthScreenState extends State<AuthScreen> {
                     padding: const EdgeInsets.only(
                       top: 15.0,
                       bottom: 30.0,
-                      left: 30.0,
-                      right: 30.0,
                     ),
-                    child: Row(
+                    child: Column(
-                      mainAxisAlignment:
+                      children: [
-                          (widget.previousButtonBuilder != null &&
+                        Row(
-                                  previousButton == null)
+                          mainAxisAlignment: MainAxisAlignment.center,
-                              ? MainAxisAlignment.spaceAround
-                              : widget.steps.first != step
-                                  ? MainAxisAlignment.spaceBetween
-                                  : MainAxisAlignment.end,
                           children: [
                             if (widget.steps.first != step)
                               if (widget.previousButtonBuilder == null) ...[
@@ -172,16 +166,22 @@ class _AuthScreenState extends State<AuthScreen> {
                                         size: 18,
                                       ),
                                       Padding(
-                                    padding: const EdgeInsets.only(left: 4.0),
+                                        padding:
+                                            const EdgeInsets.only(left: 4.0),
                                         child: Text(widget.previousBtnTitle),
                                       ),
                                     ],
                                   ),
                                 ),
                               ] else if (previousButton != null) ...[
-                            previousButton
+                                Padding(
+                                  padding: const EdgeInsets.all(8.0),
+                                  child: previousButton,
+                                )
                               ],
-                        widget.nextButtonBuilder?.call(
+                            Padding(
+                              padding: const EdgeInsets.all(8.0),
+                              child: widget.nextButtonBuilder?.call(
                                     () async {
                                       await onNext(step);
                                     },
@@ -210,10 +210,17 @@ class _AuthScreenState extends State<AuthScreen> {
                                       ],
                                     ),
                                   ),
+                            ),
+                          ],
+                        ),
+                        if (widget.loginButton != null)
+                          Padding(
+                            padding: const EdgeInsets.only(top: 20.0),
+                            child: widget.loginButton!,
+                          ),
                       ],
                     ),
                   ),
-                  if (widget.loginButton != null) widget.loginButton!,
                 ],
               ),
           ],

lib/src/model/auth_drop_down.dart

@@ -0,0 +1,59 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_registration/flutter_registration.dart';
+
+class AuthDropdownField extends AuthField {
+  AuthDropdownField({
+    required super.name,
+    required this.items,
+    required this.onChanged,
+    this.dropdownDecoration,
+    this.padding = const EdgeInsets.all(8.0),
+    this.textStyle,
+    this.icon = const Icon(Icons.keyboard_arrow_down),
+    required super.value,
+  }) {
+    selectedValue = value ?? items.first;
+  }
+
+  final List<String> items;
+  final Function(String?) onChanged;
+  String? selectedValue;
+  final InputDecoration? dropdownDecoration;
+  final EdgeInsets padding;
+  final TextStyle? textStyle;
+  final Icon icon;
+
+  @override
+  Widget build() {
+    return Padding(
+      padding: padding,
+      child: DropdownButtonFormField<String>(
+        icon: icon,
+        style: textStyle,
+        value: selectedValue,
+        decoration: dropdownDecoration,
+        items: items.map((String value) {
+          return DropdownMenuItem<String>(
+            value: value,
+            child: Text(value),
+          );
+        }).toList(),
+        onChanged: (newValue) {
+          selectedValue = newValue;
+          onChanged(newValue);
+        },
+        validator: (value) {
+          if (validators.isNotEmpty) {
+            for (var validator in validators) {
+              var output = validator(value);
+              if (output != null) {
+                return output;
+              }
+            }
+          }
+          return null;
+        },
+      ),
+    );
+  }
+}