Very customisable transition to add some sauce

scale_fade_transition.dart

import 'package:flutter/material.dart';

class ScaleFadeTransition extends StatefulWidget {
  const ScaleFadeTransition({
    required this.child,
    super.key,
    this.show = false,
    this.alignment = Alignment.center,
    this.curve = Curves.easeInOut,
  });

  final Widget child;
  final bool show;
  final Alignment alignment;
  final Curve curve;

  @override
  State<ScaleFadeTransition> createState() => _ScaleFadeTransitionState();
}

class _ScaleFadeTransitionState extends State<ScaleFadeTransition>
    with SingleTickerProviderStateMixin {
  late final AnimationController _controller;
  late final Animation<double> _opacity;
  late final Animation<double> _scale;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      vsync: this,
      duration: const Duration(milliseconds: 330),
      value: widget.show ? 1 : 0,
    );

    _scale = Tween<double>(begin: 0, end: 1).animate(
      CurvedAnimation(
        parent: _controller,
        curve: widget.curve,
      ),
    );

    _opacity = Tween<double>(begin: 0, end: 1).animate(
      CurvedAnimation(
        parent: _controller,
        curve: Interval(0.3, 1, curve: widget.curve),
      ),
    );
  }

  @override
  void didUpdateWidget(covariant ScaleFadeTransition oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.show != widget.show) {
      if (widget.show) {
        _controller.forward(from: 0);
      } else {
        _controller.reverse(from: 1);
      }
    }
  }

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

  @override
  Widget build(BuildContext context) {
    return SizeTransition(
      axisAlignment: -1,
      sizeFactor: _scale,
      child: FadeTransition(opacity: _opacity, child: widget.child),
    );
  }
}