Flutter:如何使用以前的状态更新Firestore中的数据

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

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

class _MyWidgetState extends State<MyWidget> {
  String data = 'Initial data';

  void updateFirestoreData() {
    Firestore.instance
        .collection('myCollection')
        .document('myDocument')
        .updateData({'field': data})
        .then((_) {
      print('Data updated successfully');
    }).catchError((error) {
      print('Failed to update data: $error');
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Firestore Update Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(data),
            RaisedButton(
              child: Text('Update Firestore Data'),
              onPressed: () {
                setState(() {
                  data = 'New data'; // 更新状态
                });
                updateFirestoreData(); // 更新Firestore中的数据
              },
            ),
          ],
        ),
      ),
    );
  }
}