您可以使用新的TextSelectionGestureDetector类来处理文本选择手势，而不是DragSelectionUpdateCallback。

import 'package:flutter/material.dart';

class MyTextSelectionGestureDetector extends StatelessWidget {
  final TextEditingController controller;
  final Function(TextSelection) onSelectionChanged;

  MyTextSelectionGestureDetector({required this.controller, required this.onSelectionChanged});

  @override
  Widget build(BuildContext context) {
    return TextSelectionGestureDetector(
      behavior: HitTestBehavior.translucent,
      onTapDown: (_) => controller.selection = TextSelection.collapsed(offset: controller.text.length),
      onSelectionChanged: onSelectionChanged,
      child: TextField(
        controller: controller,
      ),
    );
  }
}