颤动以使用一个布尔变量

Question

我是新手。在我的项目中，根据列表（出席者列表）的长度，会有各种check_list_tile。而且我使用了一个布尔变量。现在，当我按下一个复选框时，它会自动选中所有其他复选框。请对此提供帮助（点击一个复选框不应更改除单击之外的所有其他复选框的状态）。我已经复制了所有代码，请检查check_box_list字段。

import 'package:flutter/material.dart';
import 'package:firebase_database/firebase_database.dart';
import 'dart:async';
Map map_student_data;
Iterable iter_student_data,iter_student_key;
List list_student_data,list_student_key;
 bool t=true,checkbox=false;
  List list;
  String validation="yes";
int i;
int year;
final FirebaseDatabase database = FirebaseDatabase.instance;

class IImca_attendence extends StatefulWidget {
  @override
  _IImca_attendenceState createState() => _IImca_attendenceState();
}




class _IImca_attendenceState extends State<IImca_attendence> {

  @override
void initState(){
  this.check_year();
  super.initState();


}

  DateTime date = DateTime.now();    
Future check_year()async{
  var k= await database.reference().child("NITTE/CLASS/MCA").once().then((DataSnapshot snapshot){


      Map sea=  snapshot.value;
      Iterable iter=sea.keys;
     list=iter.toList();
      list.sublist(list.length-1);
       list.sort();
       setState(() {
          year=list.length-2;       
              });
       check();
  });
}

Future check()async{
   var m=await database.reference().child("NITTE/CLASS/MCA/${list[year].toString().toUpperCase()}/STUDENT").once().then((DataSnapshot currentyear){
            map_student_data=currentyear.value;
            iter_student_data=map_student_data.values;
            iter_student_key=map_student_data.keys;
            list_student_data=iter_student_data.toList();
            list_student_key=iter_student_key.toList();
            for(i=0;i<=list_student_data.length;i++){
               bool ss=true;
            }

           });

}

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("II-MCA"),
        centerTitle: true,
        actions: <Widget>[
          IconButton(icon: Icon(Icons.refresh),onPressed: (){
            setState(() {
                  check_year();

                        });
           })
        ],
      ),

      body: 
  validation=="1"?
   new Center(
        child: Text("STUDENT DOSE NOT EXIST IN $year",style: TextStyle(color: Colors.grey,fontWeight: FontWeight.bold,fontSize: 20),),

     ):
    new ListView.builder(
      itemCount: list_student_data==null?0
      :list_student_data.length,
      itemBuilder: (BuildContext context,int index){
        var student_detail= ['NAME : ${list_student_data[index]['NAME']}','GENDER : ${list_student_data[index]['CURRENT CLASS']}','PHOTO : ${list_student_data[index]['PHOTO']}'];
        return new Container(
          child: new Center(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: <Widget>[
                new Card(
                  child: new Container(
                    child: CheckboxListTile(
                      title: Text("${list_student_key[index]}",style:TextStyle(fontWeight: FontWeight.bold,),), 
                      subtitle: Text("NAME : ${list_student_data[index]['NAME']}"),
                      value: checkbox,
                      onChanged: (val){
                        setState(() {
                               checkbox=val;  
                               if(checkbox==true){
                                 print("${list_student_data[index]['NAME']}: i am absent");
                               }if(checkbox==false){
                                 print("${list_student_data[index]['NAME']}: i am present");
                               }

                                                });

                      },

                    ),
                    padding: EdgeInsets.all(5),
                  ),
                )
              ],
            ),
          ),
        );
      }
  )

    );
  }
}

Answer 1

嗯...您正在使用全局 checkbox变量，因此，如果更改它，根据其状态，所有小部件都会相应地更改。

我建议您做的是在模型类中添加selected状态。举个例子，假设您有这个学生班（我知道您正在使用Firebase，但是为了时间我没有）

class Student {
  var name = 'foo';
  var year = '2018';
  var selected = false;

  Student(this.name);
}

该类的内部为selected状态。

现在假设您的快照给您3个学生。总是为了节省时间，我嵌入了本地数组：

class _IImca_attendenceState extends State<IImca_attendence> {
  var _students = [Student('foo'), Student('pub'), Student('beer')];
  ...

（省略号不是代码的一部分...;-]）

我建议您将状态变量放在有状态窗口小部件作用域内，而不要放在全局作用域内。

说你可以：

ListView.builder(
    itemCount: _students.length,
    itemBuilder: (BuildContext context, int index) {
        return new Container(
        child: new Center(
            child: Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: <Widget>[
                new Card(
                child: new Container(
                    child: CheckboxListTile(
                    title: Text(
                        _students[index].name,
                        style: TextStyle(
                        fontWeight: FontWeight.bold,
                        ),
                    ),
                    subtitle:
                        Text("NAME : ${_students[index].name}"),
                    value: _students[index].selected,
                    onChanged: (val) {
                        setState(() {
                        _students[index].selected = val;
                        if (!_students[index].selected) {
                            print(
                                '${_students[index].name}: i am absent');
                        }
                        if (_students[index].selected) {
                            print(
                                '${_students[index].name}: i am present');
                        }
                        });
                    },
                    ),
                    padding: EdgeInsets.all(5),
                ),
                )
            ],
            ),
        ),
        );
    }
)

您还应该使用与快照数据学生数组长度相同的bool数组...但是我建议您直接在您的Student模型上跟踪此信息。

更新

随着您对数组的使用更加舒适，我已经使用与学生列表大小相同的补充array of bool来更改代码。

您所要做的就是一个布尔值数组（不是单个值），其布尔值与学生数组的大小相同，让我们称之为list_student_present（我改用list_student_present2）

开始时，您以check function的方式初始化它：

list_student_data = iter_student_data.toList();
// This is the array you wanna use (first all false)
list_student_present = iter_student_data.map((_) => false).toList();

然后您将使用以下布尔数组检查复选框的状态：

itemBuilder: (BuildContext context, int index) {
              return new Container(
                child: new Center(
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.stretch,
                    children: <Widget>[
                      new Card(
                        child: new Container(
                          child: CheckboxListTile(
                            title: Text(
                              _students[index].name,
                              style: TextStyle(
                                fontWeight: FontWeight.bold,
                              ),
                            ),
                            subtitle:
                                Text("NAME : ${_students[index].name}"),
                            value: list_student_present[index],
                            onChanged: (val) {
                              setState(() {
                                list_student_present[index] = val;
                                if (!list_student_present[index]) {
                                  print(
                                      '${_students[index].name}: i am absent');
                                }
                                if (list_student_present[index]) {
                                  print(
                                      '${_students[index].name}: i am present');
                                }
                              });
                            },
                          ),
                          padding: EdgeInsets.all(5),
                        ),
                      )
                    ],
                  ),
                ),
              );
            }

请勿使用我的学生班级（我将继续使用它，以便能够在不使用Firebase的情况下向您显示数据），请继续使用Firebase快照中的学生数组列表。

完整代码：

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

Map map_student_data;
Iterable iter_student_data, iter_student_key;
List list_student_data, list_student_key, list_student_present, list_student_present2;
bool t = true;
List list;
String validation = "yes";
int i;
int year;

class Student {
  var name = 'foo';
  var year = '2018';
  var selected = false;

  Student(this.name);
}

class IImca_attendence extends StatefulWidget {
  @override
  _IImca_attendenceState createState() => _IImca_attendenceState();
}

class _IImca_attendenceState extends State<IImca_attendence> {
  var _students = [Student('foo'), Student('pub'), Student('beer')];
  @override
  void initState() {
    this.check_year();
    super.initState();
  }

  DateTime date = DateTime.now();
  Future check_year() async {
    Map sea = {1: 'atlantic', 2: 'pacific'};
    Iterable iter = sea.keys;
    list = iter.toList();
    list.sublist(list.length - 1);
    list.sort();
    setState(() {
      year = list.length - 2;
    });
    check();
  }

  Future check() async {
    map_student_data = {
      0: {'NAME': 'foo', 'CURRENT CLASS': 'pub', 'PHOTO': ''}
    };
    iter_student_data = map_student_data.values;
    iter_student_key = map_student_data.keys;
    list_student_data = iter_student_data.toList();
    // This is the array you wanna use
    list_student_present = iter_student_data.map((_) => false).toList();
    // This is the array for my example
    list_student_present2 = _students.map((_) => false).toList();
    list_student_key = iter_student_key.toList();
    for (i = 0; i <= list_student_data.length; i++) {
      bool ss = true;
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("II-MCA"),
          centerTitle: true,
          actions: <Widget>[
            IconButton(
                icon: Icon(Icons.refresh),
                onPressed: () {
                  setState(() {
                    check_year();
                  });
                })
          ],
        ),
        body: validation == "1"
            ? new Center(
                child: Text(
                  "STUDENT DOSE NOT EXIST IN $year",
                  style: TextStyle(
                      color: Colors.grey,
                      fontWeight: FontWeight.bold,
                      fontSize: 20),
                ),
              )
            : ListView.builder(
                itemCount: _students.length,
                itemBuilder: (BuildContext context, int index) {
                  return new Container(
                    child: new Center(
                      child: Column(
                        crossAxisAlignment: CrossAxisAlignment.stretch,
                        children: <Widget>[
                          new Card(
                            child: new Container(
                              child: CheckboxListTile(
                                title: Text(
                                  _students[index].name,
                                  style: TextStyle(
                                    fontWeight: FontWeight.bold,
                                  ),
                                ),
                                subtitle:
                                    Text("NAME : ${_students[index].name}"),
                                value: list_student_present2[index],
                                onChanged: (val) {
                                  setState(() {
                                    list_student_present2[index] = val;
                                    if (!list_student_present2[index]) {
                                      print(
                                          '${_students[index].name}: i am absent');
                                    }
                                    if (list_student_present2[index]) {
                                      print(
                                          '${_students[index].name}: i am present');
                                    }
                                  });
                                },
                              ),
                              padding: EdgeInsets.all(5),
                            ),
                          )
                        ],
                      ),
                    ),
                  );
                }));
  }
}

我真的不喜欢这种解决方案。我建议您创建代表您的Firebase模型的PODO（纯旧Dart对象），并从Firebase快照中反序列化它们。