如何在flutter中更新列子onDragComplete

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Draggable Example'),
        ),
        body: Center(
          child: DraggableWidget(),
        ),
      ),
    );
  }
}

class DraggableWidget extends StatefulWidget {
  @override
  _DraggableWidgetState createState() => _DraggableWidgetState();
}

class _DraggableWidgetState extends State<DraggableWidget> {
  Color _color = Colors.blue;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onPanUpdate: (details) {
        setState(() {
          // 更新位置
          RenderBox box = context.findRenderObject() as RenderBox;
          Offset offset = box.localToGlobal(details.localPosition);
          print(offset);
        });
      },
      child: Container(
        width: 100,
        height: 100,
        color: _color,
        child: Center(
          child: Text(
            'Drag Me',
            style: TextStyle(color: Colors.white),
          ),
        ),
      ),
    );
  }
}