简单介绍

flutter中Row用于水平排列，Column用于竖直排列。

使用

class LayoutDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        IconBadge(Icons.person, size: 100,),
        IconBadge(Icons.edit),
        SettingText('这是一个行模型',),
      ],
    );
  }
}

row和column的用法基本一致。

主轴mainAxis

在row中主轴方向是从左到右水平方向的，column中主轴方向是从上到下竖直的。

enum MainAxisAlignment {
  /// Place the children as close to the start of the main axis as possible.
  ///
  /// If this value is used in a horizontal direction, a [TextDirection] must be
  /// available to determine if the start is the left or the right.
  ///
  /// If this value is used in a vertical direction, a [VerticalDirection] must be
  /// available to determine if the start is the top or the bottom.
  start,

  /// Place the children as close to the end of the main axis as possible.
  ///
  /// If this value is used in a horizontal direction, a [TextDirection] must be
  /// available to determine if the end is the left or the right.
  ///
  /// If this value is used in a vertical direction, a [VerticalDirection] must be
  /// available to determine if the end is the top or the bottom.
  end,

  /// Place the children as close to the middle of the main axis as possible.
  center,

  /// Place the free space evenly between the children.
  spaceBetween,

  /// Place the free space evenly between the children as well as half of that
  /// space before and after the first and last child.
  spaceAround,

  /// Place the free space evenly between the children as well as before and
  /// after the first and last child.
  spaceEvenly,
}

1. start 开始位置

2. end结束位置

3. center 中间位置

4. spaceBetween 空间分配到子控件的之间

   
   
   spaceBetween

5. spaceAround 空间分配到子控件的周围

   
   
   spaceAround

6. spaceEvenly 空间平均分配到子控件之间

   
   
   spaceEvenly

crossAxis交叉轴

交叉轴是与主轴垂直的轴。

enum CrossAxisAlignment {
  /// Place the children with their start edge aligned with the start side of
  /// the cross axis.
  ///
  /// For example, in a column (a flex with a vertical axis) whose
  /// [TextDirection] is [TextDirection.ltr], this aligns the left edge of the
  /// children along the left edge of the column.
  ///
  /// If this value is used in a horizontal direction, a [TextDirection] must be
  /// available to determine if the start is the left or the right.
  ///
  /// If this value is used in a vertical direction, a [VerticalDirection] must be
  /// available to determine if the start is the top or the bottom.
  start,

  /// Place the children as close to the end of the cross axis as possible.
  ///
  /// For example, in a column (a flex with a vertical axis) whose
  /// [TextDirection] is [TextDirection.ltr], this aligns the right edge of the
  /// children along the right edge of the column.
  ///
  /// If this value is used in a horizontal direction, a [TextDirection] must be
  /// available to determine if the end is the left or the right.
  ///
  /// If this value is used in a vertical direction, a [VerticalDirection] must be
  /// available to determine if the end is the top or the bottom.
  end,

  /// Place the children so that their centers align with the middle of the
  /// cross axis.
  ///
  /// This is the default cross-axis alignment.
  center,

  /// Require the children to fill the cross axis.
  ///
  /// This causes the constraints passed to the children to be tight in the
  /// cross axis.
  stretch,

  /// Place the children along the cross axis such that their baselines match.
  ///
  /// If the main axis is vertical, then this value is treated like [start]
  /// (since baselines are always horizontal).
  baseline,
}

和主轴参数类似，用来改变主轴垂直方向的位置。