final

lib/utils/shop_scroll_position.dart

@@ -11,17 +11,17 @@ import 'shop_scroll_coordinator.dart';
 class ShopScrollPosition extends ScrollPosition
     implements ScrollActivityDelegate {
   final ShopScrollCoordinator coordinator; // 协调器
-  ScrollDragController _currentDrag;
+  ScrollDragController? _currentDrag;
   double _heldPreviousVelocity = 0.0;
 
   ShopScrollPosition(
-      {@required ScrollPhysics physics,
-      @required ScrollContext context,
+      {required ScrollPhysics physics,
+      required ScrollContext context,
       double initialPixels = 0.0,
       bool keepScrollOffset = true,
-      ScrollPosition oldPosition,
-      String debugLabel,
-      @required this.coordinator})
+      ScrollPosition? oldPosition,
+      String? debugLabel,
+      required this.coordinator})
       : super(
           physics: physics,
           context: context,
@@ -40,7 +40,7 @@ class ShopScrollPosition extends ScrollPosition
 
   @override
   double setPixels(double newPixels) {
-    assert(activity.isScrolling);
+    assert(activity!.isScrolling);
     return super.setPixels(newPixels);
   }
 
@@ -51,13 +51,13 @@ class ShopScrollPosition extends ScrollPosition
       goIdle();
       return;
     }
-    activity.updateDelegate(this);
+    activity!.updateDelegate(this);
     final ShopScrollPosition typedOther = other as ShopScrollPosition;
     _userScrollDirection = typedOther._userScrollDirection;
     assert(_currentDrag == null);
     if (typedOther._currentDrag != null) {
       _currentDrag = typedOther._currentDrag;
-      _currentDrag.updateDelegate(this);
+      _currentDrag?.updateDelegate(this);
       typedOther._currentDrag = null;
     }
   }
@@ -131,14 +131,14 @@ class ShopScrollPosition extends ScrollPosition
   }
 
   @override
-  void beginActivity(ScrollActivity newActivity) {
+  void beginActivity(ScrollActivity? newActivity) {
     _heldPreviousVelocity = 0.0;
     if (newActivity == null) return;
     assert(newActivity.delegate == this);
     super.beginActivity(newActivity);
     _currentDrag?.dispose();
     _currentDrag = null;
-    if (!activity.isScrolling) updateUserScrollDirection(ScrollDirection.idle);
+    if (!activity!.isScrolling) updateUserScrollDirection(ScrollDirection.idle);
   }
 
   /// 将[用户滚动方向]设置为给定值。
@@ -154,7 +154,7 @@ class ShopScrollPosition extends ScrollPosition
 
   @override
   ScrollHoldController hold(VoidCallback holdCancelCallback) {
-    final double previousVelocity = activity.velocity;
+    final double previousVelocity = activity!.velocity;
     final HoldScrollActivity holdActivity =
         HoldScrollActivity(delegate: this, onHoldCanceled: holdCancelCallback);
     beginActivity(holdActivity);
@@ -195,10 +195,10 @@ class ShopScrollPosition extends ScrollPosition
       if (coordinator.pageExpand == PageExpandState.Expanding) return;
     }
     assert(pixels != null);
-    final Simulation simulation =
+    final Simulation? simulation =
         physics.createBallisticSimulation(this, velocity);
     if (simulation != null) {
-      beginActivity(BallisticScrollActivity(this, simulation, context.vsync));
+      beginActivity(BallisticScrollActivity(this, simulation, context.vsync, true));
     } else {
       goIdle();
     }
@@ -220,8 +220,8 @@ class ShopScrollPosition extends ScrollPosition
   @override
   Future<void> animateTo(
     double to, {
-    @required Duration duration,
-    @required Curve curve,
+    required Duration duration,
+    required Curve curve,
   }) {
     if (nearEqual(to, pixels, physics.tolerance.distance)) {
       // 跳过动画，直接移到我们已经靠近的位置。