flutter Row

• Row的基本属性

  children：传入子组件的数组
  mainAxisAlignment： 子组件在水平方向上的对齐方式
  crossAxisAlignment：子组件在纵轴方向上的对齐方式
  textDirection：布局顺序，一般情况从左到右
  mainAxisSize：max,表示尽可能多的占用水平方向上的位置，min则反之
  

MainAxisAlignment.spaceEvenly MainAxisAlignment.spaceAround MainAxisAlignment.spaceBetween

• 例子

 Row(
        mainAxisAlignment: MainAxisAlignment.center,
        textDirection: TextDirection.rtl,
        children: <Widget>[
          Container(
            width: 100,
            height: 100,
            color: Colors.red,
            alignment: Alignment.center,
            child: Text("A", style: TextStyle(fontSize: 24, color: Colors.white), textDirection: TextDirection.ltr,),
          ),
          Container(
            width: 100,
            height: 100,
            color: Colors.yellow,
            alignment: Alignment.center,
            child: Text("B", style: TextStyle(fontSize: 24, color: Colors.white), textDirection: TextDirection.ltr,),
          ),
          Container(
            width: 100,
            height: 100,
            color: Colors.green,
            alignment: Alignment.center,
            child: Text("C", style: TextStyle(fontSize: 24, color: Colors.white), textDirection: TextDirection.ltr,),
          ),
        ],
      ),