动态更改AlertDialog标题（showDialog（））

Question

我正在向用户显示一个对话框，我想在单击对话框的正面按钮时更改对话框的标题但是我该怎么做。

由于对话框已在屏幕上显示，setState()将无法执行任何操作。

码：

String title = "Old Title" // member variable

RaisedButton(onPressed: (){
    showDialog(context: context, builder: (context) {
      return AlertDialog(title: Text(title), actions: <Widget>[FlatButton(onPressed: () {
        setState(() => title = "New Title");
      }, child: Text("Change"))],);
    });
}, child: Text("Change"),)

Answer 1

你可以创建一个返回StatefulWidget的AlertDialog。点击更改按钮时，setState将更新对话框的文本值。

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Dynamic Dialog',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Dynamic Dialog'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'Press the FAB to present the dialog!',
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          showDialog(
              context: context,
              builder: ((BuildContext context) {
                return DynamicDialog(title: 'Original Title');
              }));
        },
        tooltip: 'Show Dialog',
        child: Icon(Icons.add),
      ),
    );
  }
}

class DynamicDialog extends StatefulWidget {
  DynamicDialog({this.title});

  final String title;

  @override
  _DynamicDialogState createState() => _DynamicDialogState();
}

class _DynamicDialogState extends State<DynamicDialog> {
  String _title;

  @override
  void initState() {
    _title = widget.title;
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: Text(_title),
      actions: <Widget>[
        FlatButton(
            onPressed: () {
              final newText = 'Updated Title!';
              setState(() {
                _title = newText;
              });
            },
            child: Text('Change'))
      ],
    );
  }
}

Answer 2

您可以这样做 - 无需创建其他小部件

RaisedButton(
  onPressed: () {
    showDialog(
        context: context,
        builder: (context) {
          StreamController<String> controller = StreamController<String>.broadcast();
          return AlertDialog(
            title: StreamBuilder(
              stream: controller.stream,
              builder: (BuildContext context, AsyncSnapshot<String> snapshot){
                      return Text(snapshot.hasData ? snapshot.data : 'Title');
              }),
            actions: [
              FlatButton(
                  onPressed: () {
                    controller.add('New Title');
                  },
                  child: Text('Change'))
            ],
          );
         });
  },
  child: Text('Change'),
);