Question

我是新手，所以我想知道如何在我的drpdownList上应用onSaved方法。请帮忙！

              Row(
                          children: <Widget>[
                            Container(
                              width: MediaQuery.of(context).size.width*.3,
                              child: Text('Départ:', style: TextStyle(fontWeight: FontWeight.bold, fontSize: 15),
                              ),
                            ),
                            Container(
                              width: MediaQuery.of(context).size.width*.5,

                                child: _fieldDropDown(_citiesdept, 0, 'depart'),
                                // onSaved: (value) => _citiesdept = value,


                            )
                          ],
                        ),

Answer 1

这可以解决您的问题吗？

如果要回调小部件，则需要：

更改

_fieldDropDown(List theList, int resultPosition, var dbField) {
// to 
_fieldDropDown(List theList, int resultPosition, var dbField, void Function(dynamic newValue) callback) {

在需要时在dropDown中拨打电话...

setState(() {

                  this.resultsList[resultPosition] = newValue;

// HERE is the callback:     
                  callback(newValue);

                  state.didChange(newValue);

                  print(

                      'The List result = ' + this.resultsList[resultPosition]);

                  //write newValue to a database field, which can be used in the override init to set the field originally

                });

并根据需要使用它，例如...

Container(
     width: MediaQuery.of(context).size.width*.5,
     child: _fieldDropDown(_citiesdept, 0, 'depart'),
     callback: (value) => print(value),

如何在下拉列表中应用onSaved方法

1 个答案: