Flutter-未為“物件”型別定義運算子“[]”。-小部件不顯示記錄

我正在嘗試進行復合查詢。如果這個有效，那么我想在 listView.builder 中顯示結果。記錄顯示不正確。我不懂為什么。我必須顯示使用查詢找到的每個檔案的名稱欄位。我嘗試了不同的選項，但結果也是一個錯誤。謝謝你。

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

class LoadDataFromFirestore extends StatefulWidget {
  const LoadDataFromFirestore({super.key});

  @override
 State<LoadDataFromFirestore> createState() => _LoadDataFromFirestoreState();
}

class _LoadDataFromFirestoreState extends State<LoadDataFromFirestore> {

  QuerySnapshot? querySnapshot;

  @override
  void initState() {
    super.initState();
    myQuery().then((results) {
      setState(() {
        querySnapshot = results;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: _showDrivers(),
    );
  }

  Widget _showDrivers() {

    if (querySnapshot != null) {
      return ListView.builder(
        primary: false,
        itemCount: querySnapshot?.docs.length,
        padding: const EdgeInsets.all(12),
        itemBuilder: (context, i) {
          return Column(
            children: <Widget>[

              Text(querySnapshot!.docs[i].data().toString()),
            ],
          );
        },
      );
    } else {
      return const Center(
        child: CircularProgressIndicator(),
      );
    }
  }

  Future myQuery () async{
    final uid = FirebaseAuth.instance.currentUser!.uid;
    final path = 'Users/$uid/allTasks';

    final currentQuery = FirebaseFirestore.instance.collection(path);
    Query statusQuery = currentQuery.where('status', isEqualTo: 'Next Action');
    Query importantQuery = statusQuery.where('important', isEqualTo: 'False');

    final snapshot = await importantQuery.get();

    final data = snapshot.docs;
    if(data.isNotEmpty){
      for(var i =0; i < data.length; i  ){
        print(data[i].data());
        return Text(data[i]['name']);
      }
      return data;
    }
  }
}

uj5u.com熱心網友回復：

由于我無法對此進行測驗，我的猜測是視圖沒有正確重繪 ，因為您使用了一個函式來獲取該小部件。此外，您將回傳一個小部件（文本），而不是 QuerySnapshot 型別的預期回應。此外，您data最后回傳的是串列而不是快照。

請繼續嘗試：

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

class LoadDataFromFirestore extends StatefulWidget {
  const LoadDataFromFirestore({super.key});

  @override
 State<LoadDataFromFirestore> createState() => _LoadDataFromFirestoreState();
}

class _LoadDataFromFirestoreState extends State<LoadDataFromFirestore> {

  QuerySnapshot? querySnapshot;

  @override
  void initState() {
    super.initState();
    myQuery().then((results) {
      setState(() {
        querySnapshot = results;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: querySnapshot != null ? ListView.builder(
        primary: false,
        itemCount: querySnapshot?.docs.length,
        padding: const EdgeInsets.all(12),
        itemBuilder: (context, i) {
          return ListTile(
           title: Text(querySnapshot!.docs[i].data().toString()),
          );
        },
      ) : Center(
        child: CircularProgressIndicator(),
      )
    );
  }

  Future myQuery () async{
    final uid = FirebaseAuth.instance.currentUser!.uid;
    final path = 'Users/$uid/allTasks';

    final currentQuery = FirebaseFirestore.instance.collection(path);
    Query statusQuery = currentQuery.where('status', isEqualTo: 'Next Action');
    Query importantQuery = statusQuery.where('important', isEqualTo: 'False');

    final snapshot = await importantQuery.get();

    final data = snapshot.docs;
    if(data.isNotEmpty){
      //for(var i =0; i < data.length; i  ){
      //  print(data[i].data());
      //  return Text(data[i]['name']);
      //}
      return snapshot;
    }
  }
}

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