Flutter学习Demo4

1

import ‘package:flutter/material.dart’;
import ‘package:english_words/english_words.dart’;

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

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: ‘Welcome to Flutter’, home: new RandomWords());
}
}

class RandomWords extends StatefulWidget {
@override
createState() => new RandomWordsState();
}

class RandomWordsState extends State {
final _suggestions = [];
final _saved = new Set();
final _biggerFont = const TextStyle(fontSize: 18.0);

@override
Widget build(BuildContext context) {
// final wordPair = new WordPair.random();
// return new Text(wordPair.asPascalCase);

return new Scaffold(
    appBar: new AppBar(
      title: new Text("startup Name Generator"),
    ),
    body: _buildSuggestions());

}

Widget _buildSuggestions() {
return new ListView.builder(
padding: const EdgeInsets.all(16.0),
itemBuilder: (context, i) {
if (i.isOdd) return new Divider();
final index = i ~/ 2;
if (index >= _suggestions.length) {
_suggestions.addAll(generateWordPairs().take(10));
}
return _buildRow(_suggestions[index]);
},
);
}

Widget _buildRow(WordPair pair) {
final alreadySaved = _saved.contains(pair);
return new ListTile(
title: new Text(pair.asPascalCase, style: _biggerFont),
trailing: new Icon(
alreadySaved ? Icons.favorite : Icons.favorite_border,
color: alreadySaved ? Colors.red : null,
),
onTap: () {
setState(() {
if (alreadySaved) {
_saved.remove(pair);
} else {
_saved.add(pair);
}
});
},
);
}
}
`

在此demo中出现了一个问题

就是在main函数中调用的时候没有去添加MaterialApp widget从而导致了编译器报错

This can happen because you do not have a WidgetsApp or MaterialApp widget (those widgets introduce a MediaQuery)

谢谢您的鼓励~