问如何修复"BoxConstraints强制无限宽“以及如何从列表中删除一项？

EN

import 'package:flutter/material.dart';

/// Styles

///




class Homepage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _MyHomePageState();
  }
}


class _MyHomePageState extends State<Homepage> {

  String dropdownValue = 'Normal';

  List<TextField> _playerList = new List(); //_playerList is my List name
  int playerListIndex = 0; //Count the number of times "Add" button clicked

  @override
  Widget build(BuildContext context) {
    return Scaffold(

      body: Stack(children: <Widget>[
        // To have a gradient background
        new Container(
          height: MediaQuery.of(context).size.height,
          width: MediaQuery.of(context).size.width,
          decoration: new BoxDecoration(
            gradient: new LinearGradient(
              begin: Alignment.topCenter,
              end: Alignment.bottomCenter,
              stops: [0.1, 1],
              colors: [
                Colors.redAccent[200],
                Colors.red[300],
              ],
              tileMode:
                  TileMode.repeated,
            ),
          ),

          //I need SingleChildScrollView to haven't "Overflow yellow bar on bottom screen"
          child: SingleChildScrollView(

            child: Container(

              padding: EdgeInsets.fromLTRB(20, 0, 20, 0),
              child: Center(
                child: Column(
                  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                  mainAxisSize: MainAxisSize.min,

                  children: <Widget>[
                    // Box to add big image
                    SizedBox(
                      height: 450,
                    ),



                    // DROP DOWN MENU to choose difficulty  modes
                    InputDecorator(
                      decoration: InputDecoration(
                        prefixIcon: const Icon(Icons.games),
                        filled: true,
                      ),
                      child: DropdownButtonHideUnderline(
                        child: new DropdownButton<String>(
                          value: dropdownValue,
                          hint: Text('Difficulty normal'),
                          isDense: true,
                          items: <String>['Normal', 'Easy', 'Hard']
                              .map<DropdownMenuItem<String>>((String value) {
                            return DropdownMenuItem<String>(
                              value: value,
                              child: Text(value),
                            );
                          }).toList(),
                          onChanged: (String newValue) {
                            setState(() {
                              dropdownValue = newValue;
                            });
                          },
                        ),
                      ),
                    ),

                    //Field player name 1. At least I need 1 player
                        new TextField(
                          maxLength: 20,
                          decoration: InputDecoration(
                            prefixIcon: const Icon(Icons.person),
                            filled: true,
                            hintText:"Player 1",
                            counterText: "",
                          ),
                        ),


                    //Field for other player name 2, 3, 4, ...
                    new ListView.builder(
                      padding: EdgeInsets.all(0),
                      shrinkWrap: true,
                      physics: NeverScrollableScrollPhysics(),
                      itemCount: _playerList.length,
                      itemBuilder: (context, index) {
                        TextField widget = _playerList.elementAt(index);
                        return widget;
                      }),

                    //Button to add other field text to set player name. The user can delete a player on click on "clear icon button"
                    new Align(
                      alignment: Alignment.centerRight,
                      child: FlatButton.icon(
                          color: Colors.black,
                          icon: Icon(
                            Icons.add,
                            color: Colors.white,
                            size: 18,
                          ),
                          label: Text('Add player',
                              style:
                                  TextStyle(fontSize: 12, color: Colors.white)),
                          onPressed: () {
                            setState(() {
                              playerListIndex++;
                              _playerList.add(
                                    new TextField(
                                      maxLength: 20,
                                      decoration: InputDecoration(
                                        prefixIcon: const Icon(Icons.person),
                                        suffixIcon: new IconButton(
                                            icon: Icon(Icons.clear),
                                            onPressed: () {
                                              _playerList.removeAt(playerListIndex); //Doesn't work
                                            }),
                                        filled: true,
                                        hintText: "Player $playerListIndex", //Doesn't work i would like Player 2, Player 3, ...
                                        counterText: "",
                                      ),
                                    ),
                              );
                              print(playerListIndex);
                              print(_playerList);
                              print(_playerList[0]);
                            });
                          }),
                    ),
                    new ButtonTheme(
                      minWidth: 350,
                      height: 45,
                      child: FlatButton(
                        color: Colors.black,
                        child: Text('Play',
                            style:
                                TextStyle(fontSize: 18, color: Colors.white)),
                        onPressed: () {
                          // Perform some action
                        },
                      ),
                    ),
                  ],
                ),
              ),
            ),
          ),
        ),
      ]),
    );
  }


}