如何根据Flutter中的下拉列表添加文本字段值

Question

[我还是Flutter的新手。在这里，我想从下拉列表中选择类别表单字段中的值。但是尝试定义时出现错误

child: DropdownButtonHideUnderline 

在Textformfield内部。我试图找到一个解决方案，但找不到它，因此无法自己编程。希望您能帮到我。还有其他存档方法吗？

我的代码在这里，在此先感谢您的指导。

class Home extends StatefulWidget {
@override
_HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {

 final AuthService _auth = AuthService();
 final _formKey = GlobalKey<FormState>();
 String error = '';
 bool loading = false;
 String name = '';
 String nickname = '';
 String city = '';


 @override
 Widget build(BuildContext context) {
   return Container(
    child: Scaffold(
    backgroundColor: Colors.brown[50],
    appBar: AppBar(
      title: Text('Brew Crew'),
      backgroundColor: Colors.brown[400],
      elevation: 0.0,
      actions: <Widget>[
        FlatButton.icon(
          icon: Icon(Icons.person),
          label: Text('logout'),
          onPressed: () async {
            await _auth.signOut();
          },
        ),
      ],
    ),
    body: Container(
      padding: EdgeInsets.symmetric(vertical: 20.0, horizontal: 50.0),
      child: Form(
        key: _formKey,
        child: SingleChildScrollView(
          child: Column(
            children: <Widget>[
              SizedBox(height: 20.0),
              TextFormField(
                decoration: textInputDecoration.copyWith(hintText: 'Name'),
                validator: (val) => val.isEmpty ? 'Enter your name' : null,
                onChanged: (val) {
                  setState(() => name = val);
                },
              ),
              SizedBox(height: 20.0),
              TextFormField(
                decoration: textInputDecoration.copyWith(hintText: 'NickName'),
            onChanged: (val) {
              setState(() => nickname = val);
            },
              ),
              SizedBox(height: 20.0),
              TextFormField(
                decoration: textInputDecoration.copyWith(hintText: 'City'),
                validator: (val) => val.isEmpty ? 'Enter your city' : null,
                onChanged: (val) {
                  setState(() => city = val);
                },
              ),
              SizedBox(height: 20.0),
              TextFormField(
                decoration: textInputDecoration.copyWith(hintText: 'Category'),
                validator: (val) => val.isEmpty ? 'Please select a category' : null,
                onChanged: (val) {
                  setState(() => nickname = val);
                },
              ),
              SizedBox(height: 20.0),
              RaisedButton(
                  color: Colors.pink[400],
                  child: Text(
                    'Submit',
                    style: TextStyle(color: Colors.white),
                  ),
                  onPressed: () async {

                  }
              ),
              SizedBox(height: 12.0),
              Text(
                error,
                style: TextStyle(color: Colors.red, fontSize: 14.0),
              )
            ],
          ),
        ),
      ),
    ),
  ),
);
}
}

Answer 1

这里的问题是，您不需要TextFormField，而是需要DropdownButton窗口小部件。

https://api.flutter.dev/flutter/material/DropdownButton-class.html

                  DropdownButton(
                    items: <DropdownMenuItem>[
                      DropdownMenuItem(
                        child: Text("Category I"),
                      ),
                      DropdownMenuItem(
                        child: Text("Category II"),
                      ),
                    ],
                    onChanged: (value) {

                    },
                  ),

我为此创建了一个代码笔。https://codepen.io/md-weber/pen/zYvqaGv