Merge pull request #347 from AhmedLSayed9/form_fields_on_change_call_back

Form fields onChange callback should be called on reset [Flutter core]

Author: AhmedLSayed9

packages/dropdown_button2/CHANGELOG.md

@@ -3,6 +3,7 @@
 - Fix errorStyle has no effect for DropdownButtonFormField2, closes #327.
 - DropdownRoutePage should dispose the created ScrollController [Flutter core].
 - Remove 'must be non-null' and 'must not be null' comments [Flutter core].
+- Form fields onChange callback should be called on reset [Flutter core].
 
 ## 3.0.0-beta.21
 

packages/dropdown_button2/lib/src/dropdown_button2.dart

@@ -1106,13 +1106,13 @@ class DropdownButtonFormField2<T> extends FormField<T> {
 }
 
 class _DropdownButtonFormFieldState<T> extends FormFieldState<T> {
+  DropdownButtonFormField<T> get _dropdownButtonFormField =>
+      widget as DropdownButtonFormField<T>;
+
   @override
   void didChange(T? value) {
     super.didChange(value);
-    final DropdownButtonFormField2<T> dropdownButtonFormField =
-        widget as DropdownButtonFormField2<T>;
-    assert(dropdownButtonFormField.onChanged != null);
-    dropdownButtonFormField.onChanged!(value);
+    _dropdownButtonFormField.onChanged!(value);
   }
 
   @override
@@ -1122,4 +1122,10 @@ class _DropdownButtonFormFieldState<T> extends FormFieldState<T> {
       setValue(widget.initialValue);
     }
   }
+
+  @override
+  void reset() {
+    super.reset();
+    _dropdownButtonFormField.onChanged!(value);
+  }
 }