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// Copyright 2020, the Flutter project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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import 'package:flutter/material.dart';
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void main() {
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runApp(MyApp());
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}
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// This app simulates possible null errors. Try running it and see if it fails.
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// You can then try to hot reload a few times; you should see it occasionally
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// failing and occasionally succeeding.
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class MyApp extends StatelessWidget {
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@override
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Widget build(BuildContext context) {
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// Get data from services. Note: in a real application,
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// these would be async calls, but we’re using sync calls
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// for simplicity.
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final localizedAppName = Config.getAppName();
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final temperatures = WeatherService.getTemperatures();
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return MaterialApp(
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home: Scaffold(
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appBar: AppBar(title: Text(localizedAppName)),
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body: Padding(
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padding: const EdgeInsets.all(8.0),
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child: Column(
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crossAxisAlignment: CrossAxisAlignment.start,
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children: [
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Text('Temperature next 3 days:'),
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for (final t in temperatures) Text(t.round().toString()),
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],
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),
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),
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),
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);
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}
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}
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class Config {
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static String getAppName() {
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// Imagine this looks up a localized version of the app name. We're using
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// the current time to simulate a variance in responses.
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if (DateTime.now().second.isEven) {
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return 'Weather forecast';
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} else {
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// Oops, we don't have a localization.
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return null;
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}
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}
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}
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class WeatherService {
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static List<double> getTemperatures() {
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// Imagine this makes a network call to get the current temperature.
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// We're using the current time to simulate a variance in responses.
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if (DateTime.now().millisecond.isEven) {
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return [32.2, 34.5, 31.0];
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} else {
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if ((DateTime.now().second / 10).round().isEven) {
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// Oops, we couldn't get any temperatures.
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return null;
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} else {
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// Oops, we couldn't get one of the temperatures.
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return [32.2, 34.5, null, 31.0];
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}
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}
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}
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}
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