import 'package:flutter/material.dart';class LayoutDemo extends StatelessWidget { @override Widget build(BuildContext context) {  return new Scaffold(   appBar: new AppBar(    title: new Text('層疊定位布局'),   ),   body:new Center(    child: new Stack(     children: <Widget>[      new Image.network('http://img2.cxtuku.com/00/13/12/s97783873391.jpg'),      new Positioned(       left: 35.0,       right: 35.0,       top: 45.0,       child: new Text(        'Whatever is worth doing is worth doing well. ๑•ิ.•ั๑',        style: new TextStyle(         fontSize: 20.0,         fontFamily: 'serif',        ),       ),      ),     ]    ),   ),  ); }}void main() { runApp(  new MaterialApp(   title: 'Flutter教程',   home: new LayoutDemo(),  ), );}