title: Flutter Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#eaea6 NEEDS-LAYOUT NEEDS-PAINT
body: <p>I'm using SingleChildScrollView and a Column to display a swiper and a gridview.</p>
  
  <p>If I use some other widget like text, image in my column, the app shows ok.
  But my swiper and gridview can't be shown, and report error:</p>
  
  <pre><code>I/flutter ( 4687): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
  I/flutter ( 4687): The following assertion was thrown during performLayout():
  I/flutter ( 4687): RenderFlex children have non-zero flex but incoming height constraints are unbounded.
  I/flutter ( 4687): When a column is in a parent that does not provide a finite height constraint, for example if it is
  I/flutter ( 4687): in a vertical scrollable, it will try to shrink-wrap its children along the vertical axis. Setting a
  I/flutter ( 4687): flex on a child (e.g. using Expanded) indicates that the child is to expand to fill the remaining
  I/flutter ( 4687): space in the vertical direction.
  I/flutter ( 4687): These two directives are mutually exclusive. If a parent is to shrink-wrap its child, the child
  I/flutter ( 4687): cannot simultaneously expand to fit its parent.
  I/flutter ( 4687): Consider setting mainAxisSize to MainAxisSize.min and using FlexFit.loose fits for the flexible
  I/flutter ( 4687): children (using Flexible rather than Expanded). This will allow the flexible children to size
  I/flutter ( 4687): themselves to less than the infinite remaining space they would otherwise be forced to take, and
  I/flutter ( 4687): then will cause the RenderFlex to shrink-wrap the children rather than expanding to fit the maximum
  I/flutter ( 4687): constraints provided by the parent.
  I/flutter ( 4687): The affected RenderFlex is:
  I/flutter ( 4687):   RenderFlex#1f4de relayoutBoundary=up14 NEEDS-LAYOUT NEEDS-PAINT
  I/flutter ( 4687): The creator information is set to:
  I/flutter ( 4687):   Column ← _SingleChildViewport ← IgnorePointer-[GlobalKey#ae070] ← Semantics ← Listener ←
  I/flutter ( 4687):   _GestureSemantics ← RawGestureDetector-[LabeledGlobalKey&lt;RawGestureDetectorState&gt;#e4f77] ←
  I/flutter ( 4687):   _ScrollableScope ← _ScrollSemantics-[GlobalKey#4bb86] ← RepaintBoundary ← CustomPaint ←
  I/flutter ( 4687):   RepaintBoundary ← ⋯
  </code></pre>
  
  <p>I'm used to be a uwp developer, and new to flutter.
  Can anyone help?
  Here is the code :</p>
  
  <pre><code>class _HomePageState extends State&lt;HomePage&gt; {
    final List&lt;ListItem&gt; _children;
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
          body:SingleChildScrollView(
          child: Column(
            mainAxisSize: MainAxisSize.min,
            mainAxisAlignment: MainAxisAlignment.spaceAround,
            children: &lt;Widget&gt;[
              Expanded(
                  child: Container(
                height: 200,
                child: Swiper(
                  itemBuilder: (BuildContext context, int index) {
                    return Image.network(
                      "http://via.placeholder.com/350x150",
                      fit: BoxFit.fitHeight,
                    );
                  },
                  itemCount: 5,
                  pagination: SwiperPagination(),
                  control: SwiperControl(),
                ),
              )),
              Expanded(
                child: GridView.builder(
                  gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                      crossAxisCount: 4, childAspectRatio: 1.0),
                  itemBuilder: (BuildContext context, int index) {
                    return ListItemWidget(_children[index]);
                  },
                  itemCount: _children.length,
                ),
              ),
            ],
          ),
        ),
      );
    }
  }
  </code></pre>