布局.dart

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  Widget b(BuildContext context) {
    return Center(
          child:Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisAlignment: MainAxisAlignment.center,                                        
            children: <Widget>[
              Container(
                color: Colors.blue,
                child:Text("一个产品\n欢迎你"),
              ),
              Container(
                child: new FlatButton(
                        child: Text("圆角按钮"),
                        color:Colors.red,              
                        shape: new RoundedRectangleBorder(
                          borderRadius: new BorderRadius.circular(30.0),
                        ),
                        onPressed: () {},
                  )
              ),
              Row(children: <Widget>[
                Icon(
                  Icons.star,
                  color: Colors.red[500],
                ),Icon(
                  Icons.star,
                  color: Colors.black,
                ),  
              ],),              
              Container(
                margin: const EdgeInsets.all(40),
                color: Colors.blue,
                child:Text("添加边距"),
              ),
              Row(
                 mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                 children: <Widget>[Text("均分"),Text("空间"),],),
              Container(
                color: Colors.blue,
                child:Text("登录就意味着你认了"),
              ),
              Container(
                color: Colors.red,
                //child: Text("**ccc")
                child:new Image.asset("assets/images/g.png"),
              ),
              new Expanded(
                child: new Align(
                  alignment: Alignment.bottomCenter,
                  child: new Text("沉底的组件/服务热线00001111"),
                ),
              ),        
              Container(
                color: Colors.red,
                 child: Text("把胁迫到底的组件/@copyright")                
              ),              
          ],
        ),
        );
  }
  Widget c(BuildContext context) {
    return Column(
            mainAxisAlignment: MainAxisAlignment.center,                                        
            crossAxisAlignment: CrossAxisAlignment.center,
            children: <Widget>[
              new FlatButton(
                        child: Text("圆角按钮"),
                        color:Colors.red,              
                        shape: new RoundedRectangleBorder(
                          borderRadius: new BorderRadius.circular(30.0),
                        ),
                        onPressed: () {},
                  ), 
                    new FlatButton(
                        child: Text("圆角按钮"),
                        color:Colors.red,              
                        shape: new RoundedRectangleBorder(
                          borderRadius: new BorderRadius.circular(30.0),
                        ),
                        onPressed: () {},
                  ), 
                  Text("abc"),
                  Text("def"),
                  Text("abc"),
                  Text("abc"),
                   new Expanded(
                      child: new Align(
                        alignment: Alignment.bottomCenter,
                        child: new Text("沉底的组件/服务热线00001111"),
                      ),
                    ),        
          ],
        );
  }
  Widget d(BuildContext context) {
    return Column(
      //mainAxisAlignment: MainAxisAlignment.spaceEvenly,
      children:[
      Container(color:Colors.red,child: Text("飞向天"),),
      Expanded(child: Center(child:Text("老子在中间。\n终于，中对齐了!\n充满客户区，尽量大"))),// 
      Container(color:Colors.purple,child: Text("贴着地"),)
    ]);
  }
  @override
  Widget build(BuildContext context) {
    // final wordPair = WordPair.random();
    return MaterialApp(
      title: 'Welcome',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Hello - Again'),
        ),
        body: d(context)
      ),
    );
  }
}