小编Ash*_*ery的帖子

这是我的班级

class Home extends StatelessWidget {

复选框位于此处。

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.center,
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Padding(
              padding: EdgeInsets.all(20.0),
              child: Column(
                children: <Widget>[
                  TextField(
                      controller: ctrlMotherName,
                      decoration: InputDecoration(
                          labelText: "Name of Mother",
                          border: OutlineInputBorder()
                      )
                  ),
                  SizedBox(height: 10,),
                  Checkbox(
                    value: false,
                    onChanged: (bool val){

                    },
                  ),

我无法选中该复选框。当我使用 Radiobutton 时也发现同样的问题。

这是我的Firebase数据

{
"ques": {
"Chemistry": {},
"Countries": {},
"Film": {},
"Geography": {},
"General Knowledge": {},
"Information Technology": {},
"Physics": {},
"Sports": {},
"Technology": {
"-Ki0y2ojhgAkDKVFostV": {},
"-Ki0ySAkiILNo2WSM7EO": {},
"-Ki1-8R-5gfHJGl9bDYC": {},
"-Ki1-fP2HlW0ejzVOGnD": {},
"-Ki1-vihF3xgP81UPT5t": {},
"-Ki10DSBPWIK0SAv5v8V": {},
"-Ki11-pLXVWZlv0XbKpp": {},
"-Ki11al-z6_MDBdpLGh7": {},
"-Ki11pxZvjvIl68UhVRc": {},
"-Ki124jOsYpy9bWpc7Yo": {},
"-Ki12oDiad-7X6UBTtBv": {},
"-Ki133GHJeys-J0vtdI9": {},
"-Ki13Iq62Ly_tx4tcxKa": {},
"-Ki13e4pp1Xnq7tnYa4N": {},
"-Ki142gU6ZHRkE34r0u3": {},
"-Ki14GswYf_lEji5a2PX": {},
"-Ki14WZpH5w5jnB4mZF1": {},
"-Ki14tX__g6VdmHJHi-g": {},
"-Ki15JghcU73RtW5zacV": {},
"-Ki15c91cOoRoR7h5aTL": {}
}
}
}

我想计算下可用的键数Technology 当我使用下面的代码时,得到count = 7,但是有20个键可用Technology

Query countQuery = countRef.child("ques").child("Technology");
countQuery.addChildEventListener(new ChildEventListener() { …

我只想更新指定的列，当我执行update(table).replace(model)它时会替换与主键对应的所有数据。如何在不编写自定义查询的情况下仅更新指定的列。

这是我的要求，当我单击“添加”按钮时，应生成具有三个 TextField 的动态新卡，以及如何使用动态创建的 TextEditingControllers> 分配每个 TextField，或者是否有其他方法可以从 TextField 中获取值？

final name1 = new TextField(
    controller: name1Controller,
    decoration: InputDecoration(
        labelText: 'Full Name', border: OutlineInputBorder()));

final age1 = new TextField(
    controller: age1Controler,
    keyboardType: TextInputType.number,
    decoration:
        InputDecoration(labelText: 'Age', border: OutlineInputBorder()));

final studyjob1 = new TextField(
    controller: study1Controller,
    decoration: InputDecoration(
        labelText: 'Study / Job', border: OutlineInputBorder()));

final person1Card = new Card(
  shape: RoundedRectangleBorder(
    borderRadius: BorderRadius.circular(15.0),
  ),
  elevation: 10,
  child: Padding(
    padding: EdgeInsets.only(top: 2.0, left: 6.0, right: 6.0, bottom: 2.0),
    child: Column(
      children: <Widget>[
        Text('Person 1'), …

{
  "items" : {
    "Chemistry" : {
      "-KiUOPW8TR_QcEeDbrAy" : {
        "answer" : "ssssss",
        "id" : "1",
        "question" : "sss"
      }
    },
    "Countries" : {
      "-KiUR2ilBYN5LJU6uOCf" : {
        "answer" : "ffffff",
        "id" : "1",
        "question" : "fffff"
      }
    },
    "Film" : {
      "-KiUOr7GbPhV_perbHt4" : {
        "answer" : "dddd",
        "id" : "1",
        "question" : "dd"
      }
    }
}

从以上数据中，我只想获取项目的子名称。

例如。我想得到这些名字

Chemistry 
Countries 
Film

我怎样才能做到这一点？