flutter - 如何使用 Flutter bloc 构建一个文本字段,在用户键入时将其值更新为另一个小部件?
问题描述
我正在寻找与您在 Google 字体上所拥有的内容相近的东西。https://fonts.google.com/
解决方案
我创建了一个像这样工作的示例演示
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
void main() {
// for bloc transition trace
//BlocSupervisor.delegate = SimpleBlocDelegate();
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return BlocProvider<TextUpdateBloc>(
create: (context) => TextUpdateBloc(),
child: MaterialApp(
home: Scaffold(body: DeleteWidget()),
),
);
}
}
class TextInputState {}
class TextInputInitState extends TextInputState {
String text;
TextInputInitState({this.text});
}
class TextInputDataChange extends TextInputState {
String text;
TextInputDataChange({this.text});
}
class TextEvents {}
class TextInit extends TextEvents {}
class TextChange extends TextEvents {
final String data;
TextChange({@required this.data});
}
class TextUpdateBloc extends Bloc<TextEvents, TextInputState> {
@override
get initialState => TextInputInitState(text: "");
@override
Stream<TextInputState> mapEventToState(event) async* {
if (event is TextInit) {
yield TextInputInitState(text: "");
} else if (event is TextChange) {
yield TextInputInitState(text: event.data);
}
}
}
class DeleteWidget extends StatelessWidget {
const DeleteWidget({Key key}) : super(key: key);
@override
Widget build(BuildContext context) {
final TextUpdateBloc counterBloc = BlocProvider.of<TextUpdateBloc>(context);
return Scaffold(
appBar: AppBar(
title: Text('test app'),
),
body: Container(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
TextFormField(
onChanged: (value) => counterBloc.add(TextChange(data: value)),
),
Container(
child: BlocBuilder<TextUpdateBloc, TextInputState>(
builder: (context, state) {
if (state is TextInputInitState) {
return Text(state.text.toString());
} else if (state is TextInputDataChange) {
return Text(state.text.toString());
} else {
return Text("something worng");
}
},
),
),
],
),
),
);
}
}
推荐阅读
- python - 使用 Python 按名称查找并选择一列(无 Pandas)
- arrays - Bash:在for循环中将元素添加到数组
- asp.net - 在 OAuth GrantResourceOwnerCredentials 方法中使用简单注入器时出错
- php - Yii2: 未定义变量 if $model = Model::find()->all(); 未在视图中指定
- tfs - 如何从 TFS Fortify 构建中排除 node_modules 文件夹?
- node.js - 如何在环回 4 上允许 cors?
- database - Golang Ravendb 在使用 OrderBy 时给出错误的查询结果
- java - Eclipse 4.9 STS 4 很慢而且经常卡住
- java - Java REST 客户端接收和保存 excel 响应(字节数组)时出错
- javascript - 如何在 Phaser 游戏中添加 Div