Support helperStyle/helperMaxLines/errorMaxLines for DropdownButtonFo…

packages/dropdown_button2/CHANGELOG.md

@@ -8,6 +8,7 @@
 - Fix memory leak in CurvedAnimation [Flutter core].
 - Avoid Container objects when possible for better performance [Flutter core].
 - Add semantics to dropdown menu items [Flutter core].
+- Support helperStyle/helperMaxLines/errorMaxLines for DropdownButtonFormField2.
 
 ## 3.0.0-beta.21
 

packages/dropdown_button2/lib/src/dropdown_button2.dart

@@ -1006,12 +1006,15 @@ class DropdownButtonFormField2<T> extends FormField<T> {
                   return InputDecorator(
                     decoration: const InputDecoration.collapsed(hintText: '')
                         .updateSurroundingElements(
+                      //helper: effectiveDecoration.helper,
+                      helperText: effectiveDecoration.helperText,
+                      helperStyle: effectiveDecoration.helperStyle,
+                      helperMaxLines: effectiveDecoration.helperMaxLines,
                       error: effectiveDecoration.error,
                       errorText:
                           field.errorText ?? effectiveDecoration.errorText,
                       errorStyle: effectiveDecoration.errorStyle,
-                      //helper: effectiveDecoration.helper,
-                      helperText: effectiveDecoration.helperText,
+                      errorMaxLines: effectiveDecoration.errorMaxLines,
                     ),
                     child: DropdownButtonHideUnderline(
                       child: DropdownButton2<T>._formField(
@@ -1047,21 +1050,15 @@ class DropdownButtonFormField2<T> extends FormField<T> {
                             // that surrounds the DropdownButton FormField. This setup is crucial
                             // to prevent the inkwell from covering the error or helper widget
                             // and to ensure that the menu does not open below them.
-                            .updateSurroundingElements(
-                              error: null,
-                              errorText: null,
-                              errorStyle: null,
-                              //helper: null,
-                              helperText: null,
-                            )
+                            .emptySurroundingElements
                             // This is crucial for the error border functionality to work.
                             .copyWith(
-                              error: field.hasError ||
-                                      effectiveDecoration.error != null ||
-                                      effectiveDecoration.errorText != null
-                                  ? const SizedBox.shrink()
-                                  : null,
-                            ),
+                          error: field.hasError ||
+                                  effectiveDecoration.error != null ||
+                                  effectiveDecoration.errorText != null
+                              ? const SizedBox.shrink()
+                              : null,
+                        ),
                         isEmpty: isEmpty,
                         isFocused: Focus.of(context).hasFocus,
                       ),

packages/dropdown_button2/lib/src/utils.dart

@@ -67,12 +67,15 @@ class _ConditionalDecoratedBox extends StatelessWidget {
 
 extension _InputDecorationExtension on InputDecoration {
   InputDecoration updateSurroundingElements({
-    required Widget? error,
-    required String? errorText,
-    required TextStyle? errorStyle,
     // TODO(Ahmed): Add this when it's supported by the min version of the package [Flutter>=3.22.0].
     // required Widget? helper,
     required String? helperText,
+    required TextStyle? helperStyle,
+    required int? helperMaxLines,
+    required Widget? error,
+    required String? errorText,
+    required TextStyle? errorStyle,
+    required int? errorMaxLines,
   }) {
     return InputDecoration(
       icon: icon,
@@ -130,4 +133,14 @@ extension _InputDecorationExtension on InputDecoration {
       constraints: constraints,
     );
   }
+
+  InputDecoration get emptySurroundingElements => updateSurroundingElements(
+        helperText: null,
+        helperStyle: null,
+        helperMaxLines: null,
+        error: null,
+        errorText: null,
+        errorStyle: null,
+        errorMaxLines: null,
+      );
 }