Fixing label & hint style issues

Moving to a more generic architecture
Updating the analysis_options.yaml file

lib/src/form_field.dart

@@ -0,0 +1,75 @@
+import 'package:date_field/src/field.dart';
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:intl/intl.dart';
+
+/// A [FormField] that contains a [DateTimeField].
+///
+/// This is a convenience widget that wraps a [DateTimeField] widget in a
+/// [FormField].
+///
+/// A [Form] ancestor is not required. The [Form] simply makes it easier to
+/// save, reset, or validate multiple fields at once. To use without a [Form],
+/// pass a [GlobalKey] to the constructor and use [GlobalKey.currentState] to
+/// save or reset the form field.
+class DateTimeFormField extends FormField<DateTime> {
+  DateTimeFormField({
+    Key? key,
+    FormFieldSetter<DateTime>? onSaved,
+    FormFieldValidator<DateTime>? validator,
+    DateTime? initialValue,
+    AutovalidateMode? autovalidateMode,
+    bool enabled = true,
+    TextStyle? dateTextStyle,
+    DateFormat? dateFormat,
+    DateTime? firstDate,
+    DateTime? lastDate,
+    ValueChanged<DateTime>? onDateSelected,
+    InputDecoration? decoration,
+    DatePickerEntryMode initialEntryMode = DatePickerEntryMode.calendar,
+    DatePickerMode initialDatePickerMode = DatePickerMode.day,
+    DateTimeFieldPickerMode mode = DateTimeFieldPickerMode.dateAndTime,
+  }) : super(
+          key: key,
+          initialValue: initialValue,
+          onSaved: onSaved,
+          validator: validator,
+          autovalidateMode: autovalidateMode,
+          enabled: enabled,
+          builder: (FormFieldState<DateTime> field) {
+            // Theme defaults are applied inside the _InputDropdown widget
+            final InputDecoration _decorationWithThemeDefaults =
+                decoration ?? const InputDecoration();
+
+            final InputDecoration effectiveDecoration =
+                _decorationWithThemeDefaults.copyWith(
+                    errorText: field.errorText);
+
+            void onChangedHandler(DateTime value) {
+              if (onDateSelected != null) {
+                onDateSelected(value);
+              }
+              field.didChange(value);
+            }
+
+            return DateTimeField(
+              firstDate: firstDate,
+              lastDate: lastDate,
+              decoration: effectiveDecoration,
+              initialDatePickerMode: initialDatePickerMode,
+              dateFormat: dateFormat,
+              onDateSelected: onChangedHandler,
+              selectedDate: field.value,
+              enabled: enabled,
+              mode: mode,
+              initialEntryMode: initialEntryMode,
+              dateTextStyle: dateTextStyle,
+            );
+          },
+        );
+
+  @override
+  _DateFormFieldState createState() => _DateFormFieldState();
+}
+
+class _DateFormFieldState extends FormFieldState<DateTime> {}