在 flutter 中使用 singlechildscrollview 文本框的视口未正确显示

Question

大家好，所有可以帮助我计算代码的人，

import 'package:flutter/material.dart';
import 'package:survey/widgets/widgetlist.dart';
import 'dart:ui' as ui;
class Item {
   Item(this.name);
   String name;
}



class createnewsurv extends StatefulWidget {
  @override
  _createnewsurvState createState() => _createnewsurvState();
}

class _createnewsurvState extends State<createnewsurv> {

  TextEditingController _textcontroller = new TextEditingController();
  int surveyquestionnum = 1;
  Item selectedUser;
  List<Item> users = <Item>[
     Item('Sample 1'),
     Item('Sample 2'),
     Item('Sample 3'),
     Item('Sample 4'),
  ];
  List<Item> users2 = <Item>[
    Item('Sample EMOJI 1'),
    Item('Sample EMOJI 2'),
    Item('Sample EMOJI 3'),
    Item('Sample EMOJI 4'),
  ];

  @override
  Widget _dropdownbutton (List<Item> userlist){
    return Container(
      padding: EdgeInsets.all(1),
      width: MediaQuery.of(context).size.width,
      decoration: BoxDecoration(
        border: Border.all(),
        borderRadius: BorderRadius.all(
            Radius.circular(15.0) 
        ),
      ),
      child: DropdownButton<Item>(
        underline: SizedBox(),
        isExpanded: true,
        icon: Icon(Icons.arrow_drop_down),
        hint:  Text("  SELECT FROM DROPDOWN"),
        value: selectedUser,
        onChanged: (Item Value) {
          setState(() {
            selectedUser = Value;
          });
        },
        items: userlist.map((Item user) {
          return  DropdownMenuItem<Item>(
            value: user,
            child: Row(
              children: <Widget>[
                SizedBox(width: 10,),
                Text(
                  user.name,
                  style:  TextStyle(color: Colors.black),
                ),
              ],
            ),
          );
        }).toList(),
      ),
    );
  }

  Widget build(BuildContext context) {
    final ui.Size logicalSize = MediaQuery.of(context).size;
    final double _height = logicalSize.height;
    return SafeArea(
      child: Scaffold(
        resizeToAvoidBottomInset: false,
          backgroundColor: Colors.white,
          body: SingleChildScrollView(
            child: Padding(
              padding: const EdgeInsets.all(8.0),
              child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    Text("CREATE A NEW SURVEY ",style: txtttitsize),
                    SizedBox(height: 10),
                    Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Text(" SURVEY TITLE",style: txtttitsize),
                    ),
                    _dropdownbutton(users),
                    Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Text(" SELECT EMOJI SET",style: txtttitsize),
                    ),
                    _dropdownbutton(users2),
                    Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Text(" SURVEY QUESTION #$surveyquestionnum",style: txtttitsize),
                    ),
                    TextFormField(
                      autocorrect: true,
                      controller: _textcontroller,
                      maxLines: 10,
                      onSaved: (value){
                      },
                      validator: (val){
                        if(val.isEmpty){
                          return "This page Cannot be Blank!";
                        }else{
                          return null;
                        }
                      },
                      decoration: InputDecoration(
                          labelText: "QUESTION",
                          fillColor: Colors.white,
                          border: OutlineInputBorder(
                              borderRadius: BorderRadius.circular(25)
                          )
                      ),
                    )
                  ]
              ),
            ),
          )),
    );
  }
}

这是一个不完整的代码，但如果您注意到并尝试了运行，它会显示 2 下拉小部件，由于某种原因，当我 select 它崩溃时显示“应该只有一个项目具有 [DropDownButton] 的值：错误，

下一个是 textform 字段，我希望当有人键入它时我将它包装在 singlescrollview 上，或者让视口在键入时将其屏幕聚焦到文本框，但是它已经在第三行并且已经被键盘挡住了，

我可能是错的，但我怎样才能正确地使用 singlescrollview 呢？或者是否有其他小部件可以让用户在键入时正确查看此文本框？

更新

单击任何下拉按钮后出现此错误。我用建议的答案更新了代码，它对我来说仍然是一样的。

Answer 1

您可以复制粘贴运行下面的完整代码
两个 _dropdownbutton 使用相同的 selectedUser 导致此错误
您可以使用 List<Item> selectedUser = [null, null]; 来保留结果
并传递 index 以像这样运行 _dropdownbutton(users, 0)

代码片段

 Widget _dropdownbutton(List<Item> userlist, int index) {
 ...
  child: DropdownButton<Item>(
        underline: SizedBox(),
        isExpanded: true,
        icon: Icon(Icons.arrow_drop_down),
        hint: Text("  SELECT FROM DROPDOWN"),
        value: selectedUser[index],
        onChanged: (Item Value) {
          setState(() {
            selectedUser[index] = Value;
          });
        },
 ...

 _dropdownbutton(users, 0),

 _dropdownbutton(users2, 1),

工作演示

完整代码

import 'package:flutter/material.dart';
import 'package:flutter/material.dart';
//import 'package:survey/widgets/widgetlist.dart';
import 'dart:ui' as ui;

import 'package:flutter/services.dart';

class Item {
  Item(this.name);
  String name;
}

class createnewsurv extends StatefulWidget {
  @override
  _createnewsurvState createState() => _createnewsurvState();
}

class _createnewsurvState extends State<createnewsurv> {
  TextEditingController _textcontroller = new TextEditingController();
  int surveyquestionnum = 1;
  List<Item> selectedUser = [null, null];
  List<Item> users;
  List<Item> users2;

  @override
  void initState() {
    users = <Item>[
      Item('Sample 1'),
      Item('Sample 2'),
      Item('Sample 3'),
      Item('Sample 4'),
    ];

    users2 = <Item>[
      Item('Sample EMOJI 1'),
      Item('Sample EMOJI 2'),
      Item('Sample EMOJI 3'),
      Item('Sample EMOJI 4'),
    ];
    super.initState();
  }

  @override
  Widget _dropdownbutton(List<Item> userlist, int index) {
    return Container(
      padding: EdgeInsets.all(1),
      width: MediaQuery.of(context).size.width,
      decoration: BoxDecoration(
        border: Border.all(),
        borderRadius: BorderRadius.all(Radius.circular(15.0)),
      ),
      child: DropdownButton<Item>(
        underline: SizedBox(),
        isExpanded: true,
        icon: Icon(Icons.arrow_drop_down),
        hint: Text("  SELECT FROM DROPDOWN"),
        value: selectedUser[index],
        onChanged: (Item Value) {
          setState(() {
            selectedUser[index] = Value;
          });
        },
        items: userlist.map((Item user) {
          return DropdownMenuItem<Item>(
            value: user,
            child: Row(
              children: <Widget>[
                SizedBox(
                  width: 10,
                ),
                Text(
                  user.name,
                  style: TextStyle(color: Colors.black),
                ),
              ],
            ),
          );
        }).toList(),
      ),
    );
  }

  Widget build(BuildContext context) {
    final ui.Size logicalSize = MediaQuery.of(context).size;
    final double _height = logicalSize.height;
    return SafeArea(
      child: Scaffold(
          resizeToAvoidBottomInset: false,
          backgroundColor: Colors.white,
          body: SingleChildScrollView(
            child: Padding(
              padding: const EdgeInsets.all(8.0),
              child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    Text(
                      "CREATE A NEW SURVEY ",
                    ),
                    SizedBox(height: 10),
                    Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Text(
                        " SURVEY TITLE",
                      ),
                    ),
                    _dropdownbutton(users, 0),
                    Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Text(
                        " SELECT EMOJI SET",
                      ),
                    ),
                    _dropdownbutton(users2, 1),
                    Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Text(
                        " SURVEY QUESTION #$surveyquestionnum",
                      ),
                    ),
                    TextFormField(
                      autocorrect: true,
                      controller: _textcontroller,
                      maxLines: 10,
                      onSaved: (value) {},
                      validator: (val) {
                        if (val.isEmpty) {
                          return "This page Cannot be Blank!";
                        } else {
                          return null;
                        }
                      },
                      decoration: InputDecoration(
                          labelText: "QUESTION",
                          fillColor: Colors.white,
                          border: OutlineInputBorder(
                              borderRadius: BorderRadius.circular(25))),
                    )
                  ]),
            ),
          )),
    );
  }
}

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Expanded(child: createnewsurv()),
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

在 flutter 中使用 singlechildscrollview 文本框的视口未正确显示

Viewport for the textbox is not showing properly using singlechildscrollview in flutter

flutter

singlechildscrollview