feat(types): make the callbacks type-safe

example/lib/main.dart

@@ -51,6 +51,8 @@ class _MyHomePageState extends State<MyHomePage> {
               } else if (dir == AxisDirection.down) {
                 debugPrint('onDown ${(widget as CardView).text} $index');
               }
+
+              return true;
             },
           ),
           Container(

lib/src/swipeable_cards_stack.dart

@@ -13,19 +13,21 @@ const List<Alignment> cardsAlign = [
 ];
 final List<Size> cardsSize = List.filled(3, const Size(1, 1));
 
+typedef OnCardSwiped = bool Function(
+    AxisDirection dir, int index, Widget? widget);
+
 class SwipeableCardsStack extends StatefulWidget {
   final SwipeableCardsStackController? cardController;
 
   //First 3 widgets
   final List<Widget> items;
-  final Function? onCardSwiped;
+  final OnCardSwiped? onCardSwiped;
   final double cardWidthTopMul;
   final double cardWidthMiddleMul;
   final double cardWidthBottomMul;
   final double cardHeightTopMul;
   final double cardHeightMiddleMul;
   final double cardHeightBottomMul;
-  final Function? appendItemCallback;
   final bool enableSwipeUp;
   final bool enableSwipeDown;
   final bool enableSwipeLeft;
@@ -43,7 +45,6 @@ class SwipeableCardsStack extends StatefulWidget {
     this.cardHeightTopMul = 0.6,
     this.cardHeightMiddleMul = 0.55,
     this.cardHeightBottomMul = 0.5,
-    this.appendItemCallback,
     this.enableSwipeUp = true,
     this.enableSwipeDown = true,
     this.enableSwipeLeft = true,
@@ -98,8 +99,6 @@ class _SwipeableCardsStackState extends State<SwipeableCardsStack>
       frontCardAlign = const Alignment(0.0, 0.001);
     }
 
-    shouldAnimate ??= true;
-
     if (shouldAnimate) {
       animateCards();
     }
@@ -215,8 +214,6 @@ class _SwipeableCardsStackState extends State<SwipeableCardsStack>
                       });
                     }
 
-                    shouldAnimate ??= true;
-
                     if (shouldAnimate) {
                       animateCards();
                     }