ScrollPosition.jumpTo call notifyListeners twice (flutter#53425)

nujz · web-flow · commit fcd90c0a51ef · 2020-03-31T11:26:02.000-07:00
diff --git a/packages/flutter/lib/src/widgets/scroll_position_with_single_context.dart b/packages/flutter/lib/src/widgets/scroll_position_with_single_context.dart
@@ -198,7 +198,6 @@ class ScrollPositionWithSingleContext extends ScrollPosition implements ScrollAc
     if (pixels != value) {
       final double oldPixels = pixels;
       forcePixels(value);
-      notifyListeners();
       didStartScroll();
       didUpdateScrollPositionBy(pixels - oldPixels);
       didEndScroll();
@@ -213,7 +212,6 @@ class ScrollPositionWithSingleContext extends ScrollPosition implements ScrollAc
     if (pixels != value) {
       final double oldPixels = pixels;
       forcePixels(value);
-      notifyListeners();
       didStartScroll();
       didUpdateScrollPositionBy(pixels - oldPixels);
       didEndScroll();
diff --git a/packages/flutter/test/widgets/scroll_position_test.dart b/packages/flutter/test/widgets/scroll_position_test.dart
@@ -141,6 +141,25 @@ Future<void> performTest(WidgetTester tester, bool maintainState) async {
 }
 
 void main() {
+  testWidgets('ScrollPosition jumpTo() doesn\'t call notifyListeners twice', (WidgetTester tester) async {
+    int count = 0;
+    await tester.pumpWidget(MaterialApp(
+      home: ListView.builder(
+        itemBuilder: (BuildContext context, int index) {
+          return Text('$index', textDirection: TextDirection.ltr);
+        },
+      ),
+    ));
+
+    final ScrollPosition position = tester.state<ScrollableState>(find.byType(Scrollable)).position;
+    position.addListener(() {
+      count++;
+    });
+    position.jumpTo(100);
+
+    expect(count, 1);
+  });
+
   testWidgets('whether we remember our scroll position', (WidgetTester tester) async {
     await performTest(tester, true);
     await performTest(tester, false);
