firebase - Flutter Navigator 从 firebase 推送数据

Question

我们正在尝试从我们当前在网格视图中呈现的 firebase 获取数据，但我希望能够单击网格视图中的项目并阅读有关它的更多信息。

这是我到目前为止所拥有的，也是我在 VS 中遇到的错误

The argument type 'DocumentSnapshot' can't be assigned to the parameter type 'Merchant'.

主屏幕

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

import 'dart:async';

import 'package:firebase_core/firebase_core.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

import 'package:paylaterapp/screens/GridMerchantDetails.dart';

Future<void> main() async {
  final FirebaseApp app = await FirebaseApp.configure(
    name: 'BNPL',
    options: const FirebaseOptions(
      googleAppID: '***',
      gcmSenderID: '***',
      apiKey: '***',
      projectID: '***',
    ),
  );

  final Firestore firestore = Firestore(app: app);
  await firestore.settings(timestampsInSnapshotsEnabled: true);

}

class HomeScreen extends StatelessWidget {
  HomeScreen(this.firestore);

  final Firestore firestore;

  CollectionReference get merchants => firestore.collection("merchants");

  @override
  Widget build(BuildContext context) {

    return Scaffold(
      appBar: AppBar(
        title: Text('Stores'),
      ),
      body: _gridView(),
    );
  }

  Widget _gridView() {    
    return StreamBuilder<QuerySnapshot>(
      stream: firestore.collection('merchants').orderBy('name', descending: false).snapshots(),
      builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        if (!snapshot.hasData) return const Text('Loading...');
        final int merchantCount = snapshot.data.documents.length;

        return GridView.builder(
          scrollDirection: Axis.vertical,

          itemCount: merchantCount,
          gridDelegate:
          new SliverGridDelegateWithFixedCrossAxisCount(
            crossAxisCount: 2),
            itemBuilder: (_, int index) {
            final DocumentSnapshot document = snapshot.data.documents[index];
            final dynamic logo = document['logo_url'], mainImage = document['main_image_url'];
            return
              CupertinoButton(
                onPressed: () {
                  Navigator.push(
                    context,
                    MaterialPageRoute(
                      builder: (context) => GridMerchantDetails(document),
                    ),
                  );
                },
                child: (
                  Container(
                    height: 300,
                    width: 300,
                    decoration: BoxDecoration(
                      borderRadius: BorderRadius.circular(10),
                      color: Colors.grey,
                      image: DecorationImage(
                          image: new NetworkImage(mainImage != null ? mainImage.toString() : 'https://images.unsplash.com/photo-1446844805183-9f5af45f89ee',
                          )
                      )
                    ),
                    child: Column(
                      mainAxisAlignment: MainAxisAlignment.end,
                      children: <Widget>[
                        Image.network(logo != null ? logo.toString() : 'https://images.unsplash.com/photo-1446844805183-9f5af45f89ee',
                          width: 220,
                          fit: BoxFit.fill,
                        )
                      ]
                    )
                  )
                )
            );
          },
        );
      },
    );
  }
}

class GridMerchantDetails extends StatelessWidget {
  final Merchant merchant;

  GridMerchantDetails(this.merchant);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      primary: true,
      appBar: AppBar(
        title: Text(merchant.name),
      ),
      backgroundColor: Colors.deepPurpleAccent,
      body: ListView(
        children: <Widget>[
          HeaderBanner(this.merchant),
          Container(
            padding: const EdgeInsets.fromLTRB(10.0, 0.0, 10.0, 20.0),
            child: Text(
              merchant.desc,
              style: TextStyle(
                fontSize: 13.0,
                color: Colors.white,
              ),
            ),
          ),
        ],
      ),
    );
  }        
}