Container由负责布局、绘画、定位和大小调整的几个控件组成，由LimitedBox、ConstrainedBox、 Align、Padding、DecoratedBox和Transform控件组成。

(Creates a widget that combines common painting, positioning, and sizing widgets)

Row:水平布局控件，能够将子控件水平排列

(Creates a horizontal array of children)

Column:垂直布局控件，能够将子控件垂直排列

(Creates a vertical array of children)

Expanded:强制子组件填充可用空间

(A widget that expands a child of a [Row], [Column], or [Flex])

Flexible组件:可以使Row、Column、Flex等子组件在主轴方向有填充可用空间的‘‘能力’’

(A widget that controls how a child of a [Row], [Column], or [Flex] flexes.)