Followed custom menu

main.dart

// [Author] Alex (https://github.com/AlexV525)
// [Date] 2024/03/15 10:57

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: const Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text('Press to head over the list page.'),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          Navigator.of(context).push(
            MaterialPageRoute(builder: (context) => const _ListPage()),
          );
        },
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}

class _ListPage extends StatefulWidget {
  const _ListPage();

  @override
  State<_ListPage> createState() => _ListPageState();
}

class _ListPageState extends State<_ListPage> {
  final manager = _ItemDeleteMenuManager();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text('List page'),
      ),
      body: ListView.separated(
        itemCount: 50,
        itemBuilder: (context, index) {
          final link = LayerLink();
          return CompositedTransformTarget(
            link: link,
            child: TextButton(
              onPressed: () => print(index),
              onLongPress: () {
                manager.show(
                  context: context,
                  item: index,
                  link: link,
                  onItemRemoved: () {
                    print('Removed');
                  },
                );
              },
              child: Text('$index'),
            ),
          );
        },
        separatorBuilder: (_, __) => const Divider(),
      ),
    );
  }
}

class _ItemDeleteMenuManager {
  _ItemDeleteMenuManager();

  final _itemEntries = <Object, OverlayEntry>{};

  OverlayState _getState(BuildContext context) {
    return Overlay.of(context, rootOverlay: true);
  }

  void show({
    required BuildContext context,
    required Object item,
    required LayerLink link,
    required void Function() onItemRemoved,
    VoidCallback? onCancel,
  }) {
    dismiss(context: context, item: item);
    final entry = OverlayEntry(
      builder: (context) => Stack(
        children: [
          Positioned.fill(
            child: GestureDetector(
              behavior: HitTestBehavior.translucent,
              onTapDown: (_) {
                dismiss(context: context, item: item);
              },
            ),
          ),
          CompositedTransformFollower(
            link: link,
            targetAnchor: Alignment.topCenter,
            followerAnchor: Alignment.bottomCenter,
            child: ColoredBox(
              color: Theme.of(context).colorScheme.inversePrimary,
              child: Row(
                mainAxisSize: MainAxisSize.min,
                children: AdaptiveTextSelectionToolbar.getAdaptiveButtons(
                  context,
                  [
                    ContextMenuButtonItem(
                      onPressed: () {
                        dismiss(context: context, item: item);
                      },
                      label: '删除',
                    ),
                  ],
                ).toList(),
              ),
            ),
          ),
        ],
      ),
    );
    _getState(context).insert(entry);
    _itemEntries[item] = entry;
  }

  void dismiss({required BuildContext context, required Object item}) {
    _itemEntries[item]?.remove();
    _itemEntries.remove(item);
  }
}