Added DropDownButton.onOpen and DropDownButton.onClose callbacks (F…

…ixes #437)

CHANGELOG.md

@@ -3,6 +3,7 @@ Date format: DD/MM/YYYY
 ## 4.0.1
 
 - `PaneItemAction.body` is no longer required ([#545](/~https://github.com/bdlukaa/fluent_ui/issues/545))
+- Added `DropDownButton.onOpen` and `DropDownButton.onClose` callbacks ([#437](/~https://github.com/bdlukaa/fluent_ui/issues/537))
 
 ## 4.0.0
 

lib/src/controls/inputs/dropdown_button.dart

@@ -43,6 +43,8 @@ class DropDownButton extends StatefulWidget {
     this.placement = FlyoutPlacement.center,
     this.menuShape,
     this.menuColor,
+    this.onOpen,
+    this.onClose,
   })  : assert(items.length > 0, 'You must provide at least one item'),
         super(key: key);
 
@@ -104,6 +106,20 @@ class DropDownButton extends StatefulWidget {
   /// The menu color. If null, [ThemeData.menuColor] is used
   final Color? menuColor;
 
+  /// Called when the flyout is opened
+  ///
+  /// See also:
+  ///
+  ///  * [Flyout.onClose]
+  final VoidCallback? onOpen;
+
+  /// Called when the flyout is closed
+  ///
+  /// See also:
+  ///
+  ///  * [Flyout.onClose]
+  final VoidCallback? onClose;
+
   @override
   State<DropDownButton> createState() => _DropDownButtonState();
 
@@ -167,6 +183,8 @@ class _DropDownButtonState extends State<DropDownButton> {
       position: FlyoutPosition.below,
       controller: flyoutController,
       verticalOffset: widget.verticalOffset,
+      onOpen: widget.onOpen,
+      onClose: widget.onClose,
       child: Builder(builder: (context) {
         return widget.buttonBuilder?.call(
               context,