Flutter Vikings Talk Animation Demo - RecipeListItemWrapper widget code

recipe_list_item_wrapper.dart

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

class RecipeListItemWrapper extends StatefulWidget {
  const RecipeListItemWrapper({
    Key? key,
    required this.child,
    this.keepAlive = false,
    this.scrollDirection = ScrollDirection.forward,
  }) : super(key: key);

  final Widget child;
  final bool keepAlive;
  final ScrollDirection scrollDirection;

  @override
  State<RecipeListItemWrapper> createState() => _RecipeListItemWrapperState();
}

class _RecipeListItemWrapperState extends State<RecipeListItemWrapper>
    with SingleTickerProviderStateMixin, AutomaticKeepAliveClientMixin {
  late final AnimationController animationController;
  late final Animation<double> scaleAnimation;
  late final Animation<double> perspectiveAnimation;
  late final Animation<AlignmentGeometry> alignmentAnimation;

  static const double perspectiveValue = 0.004;

  @override
  void initState() {
    super.initState();
    final int perspectiveDirectionMultiplier =
        widget.scrollDirection == ScrollDirection.forward ? -1 : 1;

    final AlignmentGeometry directionAlignment =
        widget.scrollDirection == ScrollDirection.forward
            ? Alignment.bottomCenter
            : Alignment.topCenter;

    animationController = AnimationController(
      vsync: this,
      duration: const Duration(milliseconds: 500),
    )..forward();

    scaleAnimation = Tween<double>(begin: 0.7, end: 1).animate(
      CurvedAnimation(
        parent: animationController,
        curve: const Interval(0, 0.5, curve: Curves.easeOut),
      ),
    );

    perspectiveAnimation = Tween<double>(
      begin: perspectiveValue * perspectiveDirectionMultiplier,
      end: 0,
    ).animate(
      CurvedAnimation(
        parent: animationController,
        curve: const Interval(0, 1, curve: Curves.easeOut),
      ),
    );

    alignmentAnimation = Tween<AlignmentGeometry>(
      begin: directionAlignment,
      end: Alignment.center,
    ).animate(
      CurvedAnimation(
        parent: animationController,
        curve: const Interval(0, 1, curve: Curves.easeOut),
      ),
    );
  }

  @override
  void dispose() {
    animationController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    super.build(context);
    return AnimatedBuilder(
      animation: animationController,
      child: widget.child,
      builder: (context, child) => Transform(
        transform: Matrix4.identity()
          ..setEntry(3, 1, perspectiveAnimation.value),
        alignment: alignmentAnimation.value,
        child: Transform.scale(
          scale: scaleAnimation.value,
          child: child,
        ),
      ),
    );
  }

  @override
  bool get wantKeepAlive => widget.keepAlive;
}