不看功夫，先看看效果：

效果图，为啥GIF不动呢

实现以上效果，主要是通过GestureDetector检测用户手势来处理的。通过Transform.translation调整X坐标进行处理，原理十分简单。

大致代码内容如下：
2023-06-05
增加滑动后自动关闭的动画效果

import 'package:flutter/material.dart';

class SlideMenuView extends StatefulWidget {
  const SlideMenuView(
      {super.key,
      this.maxDragDistance = 80.0,
      required this.child,
      this.background,
      required this.onDragStart});

  final double maxDragDistance;

  final Widget child;

  final Widget? background;

  final void Function() onDragStart;

  @override
  State<SlideMenuView> createState() => SlideMenuViewState();
}

class SlideMenuViewState extends State<SlideMenuView>
    with TickerProviderStateMixin {
  double _dragDistance = 0;

  late AnimationController _animController;

  Animation<double>? _animation;

  @override
  void initState() {
    _animController = AnimationController(
        duration: const Duration(milliseconds: 200), vsync: this)
      ..addListener(() {
        if (_animation == null) return;
        Future.microtask(
            () => setState(() => _dragDistance = _animation!.value));
        debugPrint("===> 动画运行中：${_animation!.value}");
      });
    super.initState();
  }

  void _updateDragDataAndUI(double moveDistance) {
    debugPrint("===> 拖动进行事件");
    _dragDistance += moveDistance;
    if (_dragDistance < -widget.maxDragDistance) {
      _dragDistance = -widget.maxDragDistance;
    } else if (_dragDistance >= 0.0) {
      _dragDistance = 0.0;
    }
    Future.microtask(() => setState(() {}));
  }

  void _dragCompleted() {
    debugPrint("===> 拖动完成事件");
    _animController.reset(); //动画重置
    if (_dragDistance < -widget.maxDragDistance / 2.0) {
      _animation = _animController
          .drive(Tween(begin: _dragDistance, end: -widget.maxDragDistance));
    } else if (_dragDistance > -widget.maxDragDistance / 2.0) {
      _animation = _animController.drive(Tween(begin: _dragDistance, end: 0.0));
    }
    Future.microtask(_animController.forward);
  }

  void closeSlideMenu() => setState(() => _dragDistance = 0);

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
        onHorizontalDragDown: (_) => widget.onDragStart(),
        onHorizontalDragStart: (_) => widget.onDragStart(),
        onHorizontalDragUpdate: (details) =>
            _updateDragDataAndUI(details.delta.dx),
        onHorizontalDragCancel: _dragCompleted,
        onHorizontalDragEnd: (_) => _dragCompleted(),
        child: Stack(children: [
          if (widget.background != null) widget.background!,
          Transform.translate(
              offset: Offset(_dragDistance, 0), child: widget.child)
        ]));
  }
}

extension SlideMenuViewExtensions on Widget {
  /// 应用侧滑菜单的效果
  Widget applySlideMenuEffect(
      {Key? key,
      double maxSlideDistance = 80.0,
      Widget? background,
      required void Function() onDragStart}) {
    return SlideMenuView(
        key: key,
        maxDragDistance: maxSlideDistance,
        onDragStart: onDragStart,
        background: background,
        child: this);
  }
}

2023-05-26

import 'package:flutter/material.dart';

class SlideMenuView extends StatefulWidget {
  const SlideMenuView(
      {super.key,
      this.maxDragDistance = 80.0,
      required this.child,
      this.background,
      required this.onDragStart});

  final double maxDragDistance;

  final Widget child;

  final Widget? background;

  final void Function() onDragStart;

  @override
  State<SlideMenuView> createState() => SlideMenuViewState();
}

class SlideMenuViewState extends State<SlideMenuView> {
  double _dragDistance = 0;

  void _updateDragDataAndUI(double moveDistance) {
    _dragDistance += moveDistance;
    if (_dragDistance <= -widget.maxDragDistance) {
      _dragDistance = -widget.maxDragDistance;
    } else if (_dragDistance >= 0.0) {
      _dragDistance = 0.0;
    }
    Future.microtask(() => setState(() {}));
  }

  void _dragCompleted() {
    if (_dragDistance < -widget.maxDragDistance / 2.0) {
      _dragDistance = -widget.maxDragDistance;
    } else if (_dragDistance > -widget.maxDragDistance / 2.0) {
      _dragDistance = 0.0;
    }
    Future.microtask(() => setState(() {}));
  }

  void closeSlideMenu() => setState(() => _dragDistance = 0);

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
        onHorizontalDragDown: (_) => widget.onDragStart(),
        onHorizontalDragStart: (_) => widget.onDragStart(),
        onHorizontalDragUpdate: (details) =>
            _updateDragDataAndUI(details.delta.dx),
        onHorizontalDragCancel: _dragCompleted,
        onHorizontalDragEnd: (_) => _dragCompleted(),
        child: Stack(children: [
          if (widget.background != null) widget.background!,
          Transform.translate(
              offset: Offset(_dragDistance, 0), child: widget.child)
        ]));
  }
}

/// 提供扩展类，让Widget直接使用视图
extension SlideMenuViewExtensions on Widget {
  Widget applySlideMenuEffect(
      {Key? key,
      double maxSlideDistance = 80.0,
      Widget? background,
      required void Function() onDragStart}) {
    return SlideMenuView(
        key: key,
        maxDragDistance: maxSlideDistance,
        onDragStart: onDragStart,
        background: background,
        child: this);
  }
}

应用案例

Container(
                  height: 80,
                  width: double.infinity,
                  color: Colors.red,
                  child: Text(widget.title))
              .applySlideMenuEffect(
                  onDragStart: () {},
                  background: Container(
                      width: double.infinity,
                      alignment: Alignment.centerRight,
                      child: const Text('删除')))

关闭菜单通过调用GloablKey来调用 closeSlideMenu方法。

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