Flutter-DropdownButtonFormField值未更新

您需要创建一个新

StatefulWidget

alertDialog

class MyDialog extends StatefulWidget {  @override  _MyDialogState createState() => _MyDialogState();}class _MyDialogState extends State<MyDialog> {  int _ratingController;  @override  Widget build(BuildContext context) {    return alertDialog(      content: Column(        mainAxisSize: MainAxisSize.min,        children: <Widget>[          TextField( controller: _eateryController, autofocus: true, decoration: InputDecoration(labelText: 'Eatery', hintText: 'eg Pizza Hut'),          ),          TextField( controller: _supplierController, decoration: InputDecoration(     labelText: 'Supplier', hintText: 'eg Deliveroo'),          ),          TextField( controller: _descriptionController, decoration: InputDecoration(     labelText: 'Description', hintText: 'eg cheese pizza'),          ),          DropdownButtonFormField<int>( value: _ratingController, items: [1, 2, 3, 4, 5]     .map((label) => DropdownMenuItem(   child: Text(label.toString()),   value: label, ))     .toList(), hint: Text('Rating'), onChanged: (value) {   setState(() {     _ratingController = value;   }); },          ),        ],      ),      actions: <Widget>[        FlatButton(          onPressed: () { _handleSubmit(_eateryController.text, _supplierController.text,     _descriptionController.text, _ratingController); Navigator.pop(context);          },          child: Text('Save'),        ),        FlatButton(          onPressed: () => Navigator.pop(context),          child: Text('Cancel'),        )      ],    );  }}

这样使用

showDialog(  context: context,  builder: (context) {    return MyDialog();  },);