Flutter Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#eaea6 NEEDS-LAYOUT NEEDS-PAINT

Question

I'm using SingleChildScrollView and a Column to display a swiper and a gridview.

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:

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<RawGestureDetectorState>#e4f77] ←
I/flutter ( 4687):   _ScrollableScope ← _ScrollSemantics-[GlobalKey#4bb86] ← RepaintBoundary ← CustomPaint ←
I/flutter ( 4687):   RepaintBoundary ← ⋯

I'm used to be a uwp developer, and new to flutter. Can anyone help? Here is the code :

class _HomePageState extends State<HomePage> {
  final List<ListItem> _children;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body:SingleChildScrollView(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          children: <Widget>[
            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,
              ),
            ),
          ],
        ),
      ),
    );
  }
}

Answer 1

You can have your Column inside a SizedBox and then wrap the SizedBox with SingleChildScrollView

For Eg:

new Scaffold(
body: SingleChildScrollView(
    child: Sizedbox(
      child: new Column(
        children: <Widget>[
          header,
          new Padding(
            child: GridView.builder(
                gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                    crossAxisCount: 4, childAspectRatio: 1.0),
                itemBuilder: (BuildContext context, int index) {
                  return ListItemWidget(_children[index]);
                },
                itemCount: _children.length,
              ),
          ),
        ],
      ),
  ),
),

Answer 2

I had exactly the same problem, and for me what worked was to wrap the swiper first with the expanded widget, and then wrap the expanded with the container with the sizes needed 1.Container 2. Expanded 3. Swiper

Answer 3

You cannot have an Expanded widget within the SingleChildScrollView which has boundless vertical dimensions.

class _HomePageState extends State<HomePage> {
  final List<ListItem> _children;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Column(
          mainAxisSize: MainAxisSize.min,
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          children: <Widget>[
            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,
              ),
            ),
          ],
      ),
    );
  }
}