如果在另一个列内的列中使用间隔器，则会出现 flutter 无界高度错误

Question

我被困住了......这是我的代码分解:

 Column(
    children: [
      Column(
        children: [
          Text('Whyy'),
          Spacer(),
          Text('crash?'),
        ],
      ),
      Text('ok'),
    ],
  ),

这会因错误而崩溃:

RenderFlex children have non-zero flex but incoming height constraints are unbounded.

When a column is in a parent that does not provide a finite heightconstraint, for example if it is in a vertical scrollable, it will tryto shrink-wrap its children along the vertical axis. Setting a flex ona child (e.g. using Expanded) indicates that the child is to expand tofill the remaining space in the vertical direction. These twodirectives are mutually exclusive. If a parent is to shrink-wrap itschild, the child cannot simultaneously expand to fit its parent.

但是为什么呢？到底为什么会崩溃？ Parent-Column 位于 Scaffold 的 body 内。

我在这里缺少什么？

如果您需要更多信息，请告诉我!

Answer 1

这是因为内列对其高度没有任何限制，因此 Spacer 小部件可以占据无限大的空间。您可以通过使用 Expanded(或任何其他高度约束小部件，如 SizedBox)包装内列的高度来设置实际约束:

Column(
  children: [
    Expanded(
      child: Column(
        children: [
          Text('No'),
          Spacer(),
          Text('crash!'),
        ],
      ),
    ),
    Text('ok'),
  ],
),