Flutter CupertinoContextMenu 的代码示范

下面是一个使用Flutter CupertinoContextMenu的示例代码：

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

class CupertinoContextMenuDemo extends StatefulWidget {
  const CupertinoContextMenuDemo({Key? key}) : super(key: key);

  @override
  _CupertinoContextMenuDemoState createState() =>
      _CupertinoContextMenuDemoState();
}

class _CupertinoContextMenuDemoState extends State<CupertinoContextMenuDemo> {
  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
  String _selectedAction = "None";

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      appBar: CupertinoNavigationBar(
        middle: Text("CupertinoContextMenu"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text("Selected Action: $_selectedAction"),
            SizedBox(height: 20),
            CupertinoContextMenu(
              child: Container(
                height: 200,
                width: 200,
                color: Colors.blue,
                child: Center(
                  child: Text(
                    "Long press to show context menu",
                    style: TextStyle(color: Colors.white),
                  ),
                ),
              ),
              actions: <Widget>[
                CupertinoContextMenuAction(
                  child: const Text('Copy'),
                  onPressed: () {
                    setState(() {
                      _selectedAction = "Copy";
                    });
                  },
                ),
                CupertinoContextMenuAction(
                  child: const Text('Cut'),
                  onPressed: () {
                    setState(() {
                      _selectedAction = "Cut";
                    });
                  },
                ),
                CupertinoContextMenuAction(
                  child: const Text('Paste'),
                  onPressed: () {
                    setState(() {
                      _selectedAction = "Paste";
                    });
                  },
                ),
              ],
            ),
          ],
        ),
      ),
    );
  }
}

在这个示例中，我们将CupertinoContextMenu嵌套在一个Container中，然后绑定了一些操作（复制、剪切、粘贴）来展示上下文菜单。当用户长按Container时，上下文菜单将出现并显示可能的操作，用户可以选择一个他们想执行的操作。如果操作被选中，则我们将 setState() 用于更新选择操作的状态。