[LinkedScrollController] Added two methods.

packages/linked_scroll_controller/CHANGELOG.md

@@ -1,3 +1,10 @@
+# 0.2.1
+
+* Add `LinkedScrollControllerGroup.applyViewportDimension` method that applies  
+  the viewportDimension of all linked controllers.
+* Add `LinkedScrollControllerGroup.notifyListeners` method that notifies  
+  the listener of all linked controllers.
+
 # 0.2.0
 
   * Stable release for null safety.

packages/linked_scroll_controller/lib/linked_scroll_controller.dart

@@ -88,6 +88,20 @@ class LinkedScrollControllerGroup {
   void resetScroll() {
     jumpTo(0.0);
   }
+
+  /// Applies the viewportDimension of all linked controllers to [value].
+  void applyViewportDimension(double value) {
+    for (final controller in _attachedControllers) {
+      controller.position.applyViewportDimension(value);
+    }
+  }
+
+  /// Notifies the scroll listener of all linked controllers.
+  void notifyListeners() {
+    for (final controller in _attachedControllers) {
+      controller.position.notifyListeners();
+    }
+  }
 }
 
 /// This class provides change notification for [LinkedScrollControllerGroup]'s

packages/linked_scroll_controller/pubspec.yaml

@@ -1,5 +1,5 @@
 name: linked_scroll_controller
-version: 0.2.0
+version: 0.2.1
 description: >
   A scroll controller that allows two or more scroll views to be in sync.
 repository: https://github.com/google/flutter.widgets/tree/master/packages/linked_scroll_controller

packages/linked_scroll_controller/test/linked_scroll_controller_test.dart

@@ -310,6 +310,52 @@ void main() {
       expect(state._controllers.offset, equals(state._letters.offset));
       expect(state._controllers.offset, equals(state._numbers.offset));
     });
+
+    testWidgets('applyViewportDimensions.', (tester) async {
+      await tester.pumpWidget(Test());
+      final state = tester.state<TestState>(find.byType(Test));
+
+      final viewportDimension = state._letters.position.viewportDimension;
+
+      // Change the viewportDimension.
+      final double changedViewportDimension = viewportDimension - 100;
+      state._controllers.applyViewportDimension(changedViewportDimension);
+
+      await tester.pumpAndSettle();
+
+      // The viewportDimension of the connected controllers should change.
+      expect(
+        state._letters.position.viewportDimension,
+        changedViewportDimension,
+      );
+      expect(
+        state._numbers.position.viewportDimension,
+        changedViewportDimension,
+      );
+    });
+
+    testWidgets('notifyListeners.', (tester) async {
+      await tester.pumpWidget(Test());
+      final state = tester.state<TestState>(find.byType(Test));
+
+      int countLettersCalls = 0;
+      int countNumbersCalls = 0;
+
+      // Add listeners.
+      state._letters.addListener(() {
+        countLettersCalls += 1;
+      });
+      state._letters.addListener(() {
+        countNumbersCalls += 1;
+      });
+
+      // Notify listeners.
+      state._controllers.notifyListeners();
+
+      // The listener of the registered ScrollController should be called once.
+      expect(countLettersCalls, 1);
+      expect(countNumbersCalls, 1);
+    });
   });
 }