Flutter框架解决盒约束widget和assets里加载资产技术

flutter:
  assets:
    - assets/my_icon.png
    - assets/background.png

import 'dart:async' show Future;
import 'package:flutter/services.dart' show rootBundle;
Future<String> loadAsset() async {
  return await rootBundle.loadString('assets/config.json');
}

 new AssetImage('icons/heart.png', package: 'my_icons')

class ExampleWidget extends StatefulWidget {
  ExampleWidget({Key key}) : super(key: key);
  @override
  _ExampleWidgetState createState() => new _ExampleWidgetState();
}

class _ExampleWidgetState extends State<ExampleWidget> {
  final TextEditingController _controller = new TextEditingController();
  @override
  Widget build(BuildContext context) {
    return new Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        new TextField(
          controller: _controller,
          decoration: new InputDecoration(
            hintText: 'Type something',
          ),
        ),
        new RaisedButton(
          onPressed: () {
            showDialog(
              context: context,
              child: new AlertDialog(
                title: new Text('What you typed'),
                content: new Text(_controller.text),
              ),
            );
          },
          child: new Text('DONE'),
        ),
      ],
    );
  }
}

import 'dart:async' show Future;
import 'package:flutter/services.dart' show rootBundle;
Future<String> loadAsset() async {
  return await rootBundle.loadString('assets/config.json');
}

 new AssetImage('icons/heart.png', package: 'my_icons')

Widget build(BuildContext context) {
  // ...
  return new DecoratedBox(
    decoration: new BoxDecoration(
      image: new DecorationImage(
        image: new AssetImage('graphics/background.png'),
        // ...
      ),
      // ...
    ),
  );
  // ...
}