Flutter Forward 2023: Example of adding a custom button to a TextField's context menu on all platforms.

main.dart

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(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Forward 2023'),
    );
  }
}

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

  final String title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        child: Padding(
          padding: const EdgeInsets.all(12.0),
          child: TextField(
            contextMenuBuilder: (context, editableTextState) {
              return AdaptiveTextSelectionToolbar.buttonItems(
                anchors: editableTextState.contextMenuAnchors,
                buttonItems: [
                  ...editableTextState.contextMenuButtonItems,
                  ContextMenuButtonItem(
                    label: 'Share',
                    onPressed: () { },
                  ),
                ],
              );
            },
          ),
        ),
      ),
    );
  }
}