1、Center介绍

Center将子控件放在其内部中心，里面只能放一个child，但是child里面可以放Container

Center继承勒Align，然后Align默认是center.

2、测试代码

测试1、

      @override
      Widget build(BuildContext context) {
          return MaterialApp(
              title: 'open url',
              home: Scaffold(
                appBar: AppBar(
                  // Here we take the value from the MyHomePage object that was created by
                  // the App.build method, and use it to set our appbar title.
                  title: Text('hello flutter'),
                ),
                body: Center(
                  child: Text("chenyu"),
                ),
              ),
          );
      }
    }

测试2、

      @override
      Widget build(BuildContext context) {
          return MaterialApp(
              title: 'open url',
              home: Scaffold(
                appBar: AppBar(
                  // Here we take the value from the MyHomePage object that was created by
                  // the App.build method, and use it to set our appbar title.
                  title: Text('hello flutter'),
                ),
                body: Center(
                  child: Container(
                    color: Colors.blue,
                    width: 200,
                    height: 200,
                  ),
                ),
              ),
          );
      }
    }

更多请见：http://www.mark-to-win.com/tutorial/51856.html