如何知道用户是否在Flutter中停止拖动到我的小部件之外？

import 'package:flutter/material.dart';

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  bool isDraggedOutside = false;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onPanEnd: (details) {
        setState(() {
          isDraggedOutside = !context.findRenderObject().paintBounds
              .contains(details.globalPosition);
        });
      },
      child: Container(
        width: 200,
        height: 200,
        color: isDraggedOutside ? Colors.red : Colors.green,
        child: Center(
          child: Text(
            isDraggedOutside ? 'Dragged outside' : 'Dragged inside',
            style: TextStyle(fontSize: 20),
          ),
        ),
      ),
    );
  }
}