相关疑难解决方法(0)

我正在尝试为我的Flutter应用程序构建一个简单的登录页面.我已经成功构建了TextFields和Login/Signin按钮.我想添加一个水平ListView.当我运行代码时,我的元素消失,如果我没有ListView,它再次没问题.我该怎么做才能正确？

return new MaterialApp(
        home: new Scaffold(
          appBar: new AppBar(
            title: new Text("Login / Signup"),
          ),
          body: new Container(
            child: new Center(
              child: new Column(
              mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                  new TextField(
                    decoration: new InputDecoration(
                      hintText: "E M A I L    A D D R E S S"
                    ),
                  ),
                  new Padding(padding: new EdgeInsets.all(15.00)),
                  new TextField(obscureText: true,
                    decoration: new InputDecoration(
                      hintText: "P A S S W O R D"
                    ),
                    ),
                  new Padding(padding: new EdgeInsets.all(15.00)),
                  new TextField(decoration: new InputDecoration(
                    hintText: "U …

在尝试实现flutter-firebase 时，ListView.builder未能显示！

请注意，当我尝试在没有ListView.builder它的情况下显示第一个元素时，它工作正常，即错误仅与此代码块相关：

return ListView.builder(
    itemCount: snapshot.data.documents.length,
    padding: const EdgeInsets.only(top: 10.0),
    itemExtent: 25.0,
    itemBuilder: (context, index) {
    DocumentSnapshot ds = snapshot.data.documents[index];
    return Text(" ${ds['name']} ${ds['vote']}");
});

我的完整代码是：

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

void main() => runApp(MyApp(
  textInput: Text("Text Widget"),
));

class MyApp extends StatefulWidget {
  final Widget textInput;
  MyApp({this.textInput});

  @override
  State<StatefulWidget> createState() => MyAppState();
}

class MyAppState extends State<MyApp> {
  bool checkBoxValue = false;
  @override
  Widget build(BuildContext ctxt) {
    return new MaterialApp(
      home: SafeArea(
        child: …