How to solve: How can I tightly wrap a Column of widgets inside a Card?

Question

Asked by Reagankm on January 25, 2017 (source).

I have a page of my app that consists solely of a Card that holds a Column at the end of which is a MaterialList. Even if my list only has one or two items, the Card extends its vertical space to the bottom of the screen rather than stopping at the end of the list items. The Column documentation suggests this is normal Column behavior ("Layout each child a null or zero flex factor (e.g., those that are not Expanded) with unbounded vertical constraints"). I thought wrapping the list in a Flexible might achieve my desired effect but when I tried I got the following error:

RenderFlex children have non-zero flex but incoming height constraints are unbounded.
I/flutter (11469): When a column is in a parent that does not provide a finite height constraint, for example if it is
I/flutter (11469): in a vertical scrollable, it will try to shrink-wrap its children along the vertical axis. Setting a
I/flutter (11469): flex on a child (e.g. using a Flexible) indicates that the child is to expand to fill the remaining
I/flutter (11469): space in the vertical direction.
I/flutter (11469): These two directives are mutually exclusive. If a parent is to shrink-wrap its child, the child
I/flutter (11469): cannot simultaneously expand to fit its parent.

I'm clearly misunderstanding something about how this layout is supposed to work.

Here is sample code of what I have now as the body of the Scaffold for this page:

new Container(
// Outer container so we can set margins and padding for the cards
// that will hold the rest of the view.
alignment: FractionalOffset.topCenter,
margin: new EdgeInsets.only(top: style.wideMargin),
padding: new EdgeInsets.symmetric(horizontal: style.defaultMargin),
child: new Card(
  child: new Column(
    children: [
      new CustomHeader(), // <-- a Row with some buttons in it
      new Divider(),
      new MaterialList(
        type: MaterialListType.twoLine,
        children: listItems, // <-- a list of custom Rows
      ),
    ],
  ),
),

)

How can I have a Card that tightly wraps a Column of widgets?

Answer

Question answered by Adam B (source).

By default, Column expands to fill the maximum vertical space. You can change this behavior by setting the mainAxisSize property to MainAxisSize.min, which causes the Column to take up only the minimum amount of vertical space it needs to fit its children.

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