android - Flutter-在子孙中调用setState后重建父对象

Question

我有一类带有主页，另一类带有Dialog(当用户单击 float 按钮时出现)。

从对话框中的下拉菜单中选择某项后，主页上有一个TextField，我想立即更新它(该对话框与TextField距离很远，在另一个类中)。我如何告诉flutter重建该(父)类？

它对我不起作用，在按您的书写方式应用更改后，我的下拉菜单中没有选项，并且无法单击。

DropdownButton<double>(
   hint: Text("Specify sleep lenght"),
   value: dropdownValue,
   onChanged: onValueChange,
   items: availableLengthHours.map((l) {
     return DropdownMenuItem(
        child: new Center(child: Text(l.toString())),
        value: l,
     );
   }).toList(),
),

Answer 1

Jacek，不确定您尝试了什么，但是实现所需目标的一种方法是使用对话框选项作为Navigator.push的结果。这是一个简单的例子，

class MyApp extends StatefulWidget {
  @override
  MyAppState createState() => MyAppState();
}

class MyAppState extends State<MyApp> {
  String text = 'Original text';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
          appBar: AppBar(title: Text('Test'),),
            body: Center(
                        child: Column(
                            mainAxisAlignment: MainAxisAlignment.center,
                            children: [
                          Padding(
                              padding: const EdgeInsets.only(
                                  left: 10.0, right: 10.0),
                              child: Column(children: <Widget>[
                                Text(text, style: TextStyle(fontSize: 18.0, fontWeight: FontWeight.bold)),
                              ]))
                        ])),
          floatingActionButton: Builder( builder: (context) => FloatingActionButton(
            child: Icon(Icons.refresh),
            onPressed: () async {
              update(context);
            },
          )),
        ),
    );
  }

  update(BuildContext context) async {
    final result = await Navigator.push(
      context,
      MaterialPageRoute(builder: (context) => Dialog()),
    );

    setState(() {
      text= result;
    });
  }
}

class Dialog extends StatelessWidget {
  String dropdownValue = 'Updated item 1';
  @override
  Widget build(BuildContext context) {
    return AlertDialog(
            title: new Text('Test dialog'),
            content: DropdownButton<String>(
              value: dropdownValue,
              icon: Icon(Icons.arrow_downward),
              iconSize: 24,
              elevation: 16,
              style: TextStyle(color: Colors.deepPurple),
              underline: Container(
                height: 2,
                color: Colors.deepPurpleAccent,
              ),
              onChanged: (String newValue) {
                Navigator.pop(context, newValue);
              },
              items: <String>[
                'Updated item 1',
                'Updated item 2',
                'Updated item 3',
                'Updated item 4'
              ].map<DropdownMenuItem<String>>((String value) {
                return DropdownMenuItem<String>(
                  value: value,
                  child: Text(value),
                );
              }).toList(),
            ),
            actions: <Widget>[
              // usually buttons at the bottom of the dialog
              new FlatButton(
                child: new Text('Cancel'),
                onPressed: () {
                  Navigator.pop(context, true);
                },
              )
            ],
          );
  }
}

希望这会好起来。