AnimatedOffset widget for Flutter — animated version of Transform.translate

animated_offset.dart

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

class AnimatedOffset extends ImplicitlyAnimatedWidget {
  /// Animated version of [Transform.translate] which automatically transitions the child's
  /// offset over a given duration whenever the given offset changes.
  ///
  /// The [curve] and [duration] arguments must not be null.
  const AnimatedOffset({
    Key? key,
    this.child,
    required this.offset,
    Curve curve = Curves.linear,
    required Duration duration,
    VoidCallback? onEnd,
  }) :
        super(key: key, curve: curve, duration: duration, onEnd: onEnd);

  /// The widget below this widget in the tree.
  ///
  /// {@macro flutter.widgets.ProxyWidget.child}
  final Widget? child;

  /// The target offset. 
  /// The child will be translated horizontally by `width * dx` and vertically by `height * dy`
  ///
  /// The offset must not be null.
  final Offset offset;

  @override
  _AnimatedOffsetState createState() => _AnimatedOffsetState();

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
  }
}

class _AnimatedOffsetState extends ImplicitlyAnimatedWidgetState<AnimatedOffset> {
  Tween<Offset>? _offset;
  late Animation<Offset> _offsetAnimation;

  @override
  void forEachTween(TweenVisitor<dynamic> visitor) {
    _offset = visitor(_offset, widget.offset, (dynamic value) => Tween<Offset>(begin: value as Offset)) as Tween<Offset>?;
  }

  @override
  void didUpdateTweens() {
    _offsetAnimation = animation.drive(_offset!);
  }

  @override
  Widget build(BuildContext context) {
    return SlideTransition(
      position: _offsetAnimation,
      child: widget.child,
    );
  }
}