Question

因此，在futurebuilder和streambuilder正常工作之前，但是我listbuilder在streambuilder中工作，所以我决定进行更改，但现在它不工作了，我在futurebuilder和streambuilder中放置了打印件，但是它们没有被打印，什么也没发生。.

我没有收到任何错误。我100％确信查询是正确的。

这是整个代码：

 import 'package:flutter/material.dart';
 import 'package:rezervisanje/globals.dart' as globals;
import 'dart:async';
import 'package:cloud_firestore/cloud_firestore.dart';

class ReserveTable extends StatefulWidget {
  @override
   _ReserveTableState createState() => _ReserveTableState();
}

class _ReserveTableState extends State<ReserveTable> 
{
  var sum;
  var step = 0;
  var hours = 0;
  var minutes = 0;
  DateTime times;
  final List<LoadList> terminlist = new List();
  final List<LoadList> items = new List();
  final formKey = GlobalKey<FormState>();
  Future<int> firebaseQuery;
  @override
  void initState() {
    super.initState();
    firebaseQuery = Firestore.instance
        .collection('salons')
        .document(globals.salonkey)
        .get()
        .then((document) {
      setState(() {
        globals.shiftstart = document.data['firstshiftstart'];
        globals.shiftend = document.data['firstshiftend'];
      });
    });
  }

   @override
  Widget build(BuildContext context) {
    if (globals.day == null) {
      globals.day = DateTime(
          DateTime.now().year, DateTime.now().month, DateTime.now().day);
    }
    times = globals.day.add(new Duration(days: -1));
    new FutureBuilder(
      future: firebaseQuery,
      builder: (context, snapshot) {
        if (snapshot.hasError) {
          print("snapErr");//not getting printed
          return new Text("${snapshot.error}");
        } else
          items.clear();
        print("SHIFTEND " + globals.shiftend.toString());//not getting printed
      },
    );
new StreamBuilder<QuerySnapshot>(
    stream: Firestore.instance
        .collection('termins')
        .where('time', isLessThanOrEqualTo: globals.day)
        .where('time', isGreaterThanOrEqualTo: times)
        .where('employeeID', isEqualTo: globals.employeeID)
        .snapshots(),
    builder: (context, AsyncSnapshot<QuerySnapshot> snapshot) {
      print("2");//not getting printed
      if (!snapshot.hasData)
        return const Text('Connecting...');
      else {
        print('3');//not getting printed
        sum = snapshot.data.documents.length;
        for (int i = 0; i < sum; i++) {
          DocumentSnapshot items = snapshot.data.documents[i];
          DateTime date = items['time'];
          terminlist.add(new LoadList(date.hour, date.minute));
        }
      }
    });

int div =
    ((globals.shiftend - globals.shiftstart) * 60 / globals.requiredtime)
        .round();
hours = globals.shiftstart;
for (var i = 0; i < div; i++) {
  if (minutes == 60) {
    minutes = 0;
    hours = hours + 1;
  }
  items.add(new LoadList(hours, minutes));
  minutes += globals.requiredtime;
}

return new Scaffold(
    appBar: new AppBar(
      title:
          new Text(globals.employee == "" ? "Reserve" : globals.employee),
      backgroundColor: Colors.deepOrange,
    ),
    drawer: new Drawer(
        child: new ListView(children: <Widget>[
      new ListTile(
          title: new Text("Close"),
          trailing: new Icon(Icons.arrow_upward),
          onTap: () {
            Navigator.of(context).pop();
          })
    ])),
    body: Card(
        child: Padding(
      padding: EdgeInsets.all(8.0),
      child: Form(
          key: formKey,
          child: new ListView.builder(
              scrollDirection: Axis.vertical,
              itemCount: items.length,
              itemBuilder: (context, index) {
                print(sum);//only this is getting printed,its null
              })),
    )));
 }
}

class LoadList {
 final hours;
 final minutes;
 LoadList(this.hours, this.minutes);
}

我一直在搜索问题几个小时，该怎么改变？谢谢！

Answer 1

这是我一起使用它们的方式：

class _PostListState extends State<PostList> {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<PostParams>(
      stream: PostBloc().param,
      builder: (BuildContext context, AsyncSnapshot<PostParams> params) {
        if (params.hasError) {
          return new Center(child: Text(Api.StreamError));
        } else {
          return new FutureBuilder(
            future: Post.get(),
            builder: (BuildContext context, AsyncSnapshot snapshot) {
              switch (snapshot.connectionState) {
                case ConnectionState.none:
                case ConnectionState.waiting:
                  return new Center(child: new CircularProgressIndicator());
                default:
                  if (snapshot.hasError)
                    return new Center(child: Text(Api.FutureError));
                  else {
                    return new ListBuilder(snapshot.data);
                  }
              }
            },
          );
        }
      },
    );
  }

通过这种方式 StreamBuilder 负责处理来自UI的参数， FutureBuilder 调用API并在结果返回时采取行动。

如果您在Stream中没有更改某些状态，则不需要StreamBuilder。

流和未来的构建器未构建

1 个答案: