From 6f2ca4025b54e9d41652ab549dc28a2eacce02dd Mon Sep 17 00:00:00 2001
From: xubaolin <xubaolin@oppo.com>
Date: Wed, 9 Jun 2021 10:39:03 +0800
Subject: [PATCH] fix a ListWheelScrollView childDelegate update bug (#82675)

---
 .../src/widgets/list_wheel_scroll_view.dart   |  4 ++-
 .../flutter/test/cupertino/picker_test.dart   | 30 ++++++++++++++---
 .../widgets/list_wheel_scroll_view_test.dart  | 33 ++++++++++++++++++-
 3 files changed, 61 insertions(+), 6 deletions(-)

diff --git a/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart b/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart
index b16699aae98..31eead2164e 100644
--- a/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart
+++ b/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart
@@ -843,8 +843,10 @@ class ListWheelElement extends RenderObjectElement implements ListWheelChildMana
     final ListWheelChildDelegate newDelegate = newWidget.childDelegate;
     final ListWheelChildDelegate oldDelegate = oldWidget.childDelegate;
     if (newDelegate != oldDelegate &&
-        (newDelegate.runtimeType != oldDelegate.runtimeType || newDelegate.shouldRebuild(oldDelegate)))
+        (newDelegate.runtimeType != oldDelegate.runtimeType || newDelegate.shouldRebuild(oldDelegate))) {
       performRebuild();
+      renderObject.markNeedsLayout();
+    }
   }
 
   @override
diff --git a/packages/flutter/test/cupertino/picker_test.dart b/packages/flutter/test/cupertino/picker_test.dart
index f56df59316e..e94f7113536 100644
--- a/packages/flutter/test/cupertino/picker_test.dart
+++ b/packages/flutter/test/cupertino/picker_test.dart
@@ -48,9 +48,32 @@ void main() {
   });
 
   group('layout', () {
+    // Regression test for https://github.com/flutter/flutter/issues/22999
+    testWidgets('CupertinoPicker.builder test', (WidgetTester tester) async {
+      Widget buildFrame(int childCount) {
+        return Directionality(
+          textDirection: TextDirection.ltr,
+          child: CupertinoPicker.builder(
+            itemExtent: 50.0,
+            onSelectedItemChanged: (_) { },
+            itemBuilder: (BuildContext context, int index) {
+              return Text('$index');
+            },
+            childCount: childCount,
+          ),
+        );
+      }
+
+      await tester.pumpWidget(buildFrame(1));
+      expect(tester.renderObject(find.text('0')).attached, true);
+
+      await tester.pumpWidget(buildFrame(2));
+      expect(tester.renderObject(find.text('0')).attached, true);
+      expect(tester.renderObject(find.text('1')).attached, true);
+    });
+
     testWidgets('selected item is in the middle', (WidgetTester tester) async {
-      final FixedExtentScrollController controller =
-          FixedExtentScrollController(initialItem: 1);
+      final FixedExtentScrollController controller = FixedExtentScrollController(initialItem: 1);
 
       await tester.pumpWidget(
         Directionality(
@@ -285,8 +308,7 @@ void main() {
     );
 
     testWidgets('a drag in between items settles back', (WidgetTester tester) async {
-      final FixedExtentScrollController controller =
-          FixedExtentScrollController(initialItem: 10);
+      final FixedExtentScrollController controller = FixedExtentScrollController(initialItem: 10);
       final List<int> selectedItems = <int>[];
 
       await tester.pumpWidget(
diff --git a/packages/flutter/test/widgets/list_wheel_scroll_view_test.dart b/packages/flutter/test/widgets/list_wheel_scroll_view_test.dart
index 1508ea99925..3a4492baa46 100644
--- a/packages/flutter/test/widgets/list_wheel_scroll_view_test.dart
+++ b/packages/flutter/test/widgets/list_wheel_scroll_view_test.dart
@@ -77,7 +77,6 @@ void main() {
       expect(tester.getSize(find.byType(ListWheelScrollView)), const Size(800.0, 600.0));
     });
 
-
     testWidgets('ListWheelScrollView needs positive magnification', (WidgetTester tester) async {
       expect(
         () {
@@ -283,6 +282,38 @@ void main() {
   });
 
   group('layout', () {
+    // Regression test for https://github.com/flutter/flutter/issues/58144
+    testWidgets('ListWheelScrollView childDelegate update test', (WidgetTester tester) async {
+      final FixedExtentScrollController controller = FixedExtentScrollController();
+      Widget buildFrame(int childCount) {
+        return Directionality(
+          textDirection: TextDirection.ltr,
+          child: ListWheelScrollView.useDelegate(
+            controller: controller,
+            itemExtent: 100.0,
+            onSelectedItemChanged: (_) { },
+            childDelegate: ListWheelChildBuilderDelegate(
+              childCount: childCount,
+              builder: (BuildContext context, int index) {
+                return SizedBox(
+                  width: 400.0,
+                  height: 100.0,
+                  child: Text(index.toString()),
+                );
+              },
+            ),
+          ),
+        );
+      }
+
+      await tester.pumpWidget(buildFrame(1));
+      expect(tester.renderObject(find.text('0')).attached, true);
+
+      await tester.pumpWidget(buildFrame(2));
+      expect(tester.renderObject(find.text('0')).attached, true);
+      expect(tester.renderObject(find.text('1')).attached, true);
+    });
+
     testWidgets("ListWheelScrollView takes parent's size with small children", (WidgetTester tester) async {
       await tester.pumpWidget(
         Directionality(