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main.dart
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main.dart
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// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
void main() {
runApp(new MaterialApp(
title: 'Inherited Widgets Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new Scaffold(
appBar: new AppBar(
title: new Text('Inherited Widget Example'),
),
body: new NamePage())));
}
// Inherited widget for managing a name
class NameInheritedWidget extends InheritedWidget {
const NameInheritedWidget({
Key key,
this.name,
Widget child}) : super(key: key, child: child);
final String name;
@override
bool updateShouldNotify(NameInheritedWidget old) {
print('In updateShouldNotify');
return name != old.name;
}
static NameInheritedWidget of(BuildContext context) {
// You could also just directly return the name here
// as there's only one field
return context.inheritFromWidgetOfExactType(NameInheritedWidget);
}
}
// Stateful widget for managing name data
class NamePage extends StatefulWidget {
@override
_NamePageState createState() => new _NamePageState();
}
// State for managing fetching name data over HTTP
class _NamePageState extends State<NamePage> {
String name = 'Placeholder';
// Fetch a name asynchonously over HTTP
_get() async {
var res = await http.get('https://jsonplaceholder.typicode.com/users');
var name = JSON.decode(res.body)[0]['name'];
setState(() => this.name = name);
}
@override
void initState() {
super.initState();
_get();
}
@override
Widget build(BuildContext context) {
return new NameInheritedWidget(
name: name,
child: const IntermediateWidget()
);
}
}
// Intermediate widget to show how inherited widgets
// can propagate changes down the widget tree
class IntermediateWidget extends StatelessWidget {
// Using a const constructor makes the widget cacheable
const IntermediateWidget();
@override
Widget build(BuildContext context) {
return new Center(
child: new Padding(
padding: new EdgeInsets.all(10.0),
child: const NameWidget()));
}
}
class NameWidget extends StatelessWidget {
const NameWidget();
@override
Widget build(BuildContext context) {
final inheritedWidget = NameInheritedWidget.of(context);
return new Text(
inheritedWidget.name,
style: Theme.of(context).textTheme.display1,
);
}
}