How can I fix the error generated by the ListView?

Question

Guys I have a question for you: I have built a PageView. In this PageView is a ListView and in this ListView is a list of widgets. But unfortunately my code doesn't work for some reason ... And I have no idea why. I'm still very new to Flutter. I would really appreciate your help. The code that generates the error is the following:

Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      body: ListView(
        children: createHomePage(
            controller: _controller,
            content: widget.content,
            title: widget.title,
            menuButtonAction: widget.menuButton,
            showShadow: widget.showShadow,
            context: context),
      ),
    );
  }
}

I would be really grateful if you could help me. The code works fine when I replace the ListView with a Colum, but then unfortunately I can't scroll ... But it has to be scrollable! I keep getting the following error:

I/flutter ( 4539): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════

I/flutter ( 4539): The following assertion was thrown building NotificationListener<KeepAliveNotification>:

I/flutter ( 4539): Incorrect use of ParentDataWidget.

I/flutter ( 4539): Expanded widgets must be placed inside Flex widgets.

I/flutter ( 4539): Expanded(no depth, flex: 1, dirty) has no Flex ancestor at all.

I/flutter ( 4539): The ownership chain for the parent of the offending Expanded was:

I/flutter ( 4539):   RepaintBoundary ← IndexedSemantics ← 
NotificationListener<KeepAliveNotification> ← KeepAlive ←

I/flutter ( 4539): AutomaticKeepAlive ← KeyedSubtree ← SliverList ← MediaQuery ← SliverPadding ← ShrinkWrappingViewport

I/flutter ( 4539): ← ⋯

I/flutter ( 4539): 

I/flutter ( 4539): The relevant error-causing widget was:

I/flutter ( 4539):   ListView

How can I solve this problem? I've tried a lot. For example, I put the list of widgets in a column and changed the ListView to a SingleChildListView, but that didn't help either. However, I got another error message. This was:

══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════

I/flutter ( 4539): The following assertion was thrown during performLayout():

I/flutter ( 4539): RenderFlex children have non-zero flex but incoming height constraints are unbounded.

I/flutter ( 4539): When a column is in a parent that does not provide a finite height constraint, for example if it is

I/flutter ( 4539): in a vertical scrollable, it will try to shrink-wrap its children along the vertical axis. Setting a

I/flutter ( 4539): flex on a child (e.g. using Expanded) indicates that the child is to expand to fill the remaining

I/flutter ( 4539): space in the vertical direction.

I/flutter ( 4539): These two directives are mutually exclusive. If a parent is to shrink-wrap its child, the child

I/flutter ( 4539): cannot simultaneously expand to fit its parent.
I/flutter ( 4539): Consider setting mainAxisSize to MainAxisSize.min and using FlexFit.loose fits for the flexible

I/flutter ( 4539): children (using Flexible rather than Expanded). This will allow the flexible children to size

I/flutter ( 4539): themselves to less than the infinite remaining space they would otherwise be forced to take, and

I/flutter ( 4539): then will cause the RenderFlex to shrink-wrap the children rather than expanding to fit the maximum

I/flutter ( 4539): constraints provided by the parent.

I/flutter ( 4539): If this message did not help you determine the problem, consider using debugDumpRenderTree():

I/flutter ( 4539):   https://flutter.dev/debugging/#rendering-layer

I/flutter ( 4539):   http://api.flutter.dev/flutter/rendering/debugDumpRenderTree.html

I/flutter ( 4539): The affected RenderFlex is:

I/flutter ( 4539):   RenderFlex#bfee3 relayoutBoundary=up15 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE(creator: Column ← RepaintBoundary ← IndexedSemantics ← NotificationListener<KeepAliveNotification> ← KeepAlive ← AutomaticKeepAlive ← KeyedSubtree ← SliverList ← MediaQuery ← SliverPadding ← ShrinkWrappingViewport ← IgnorePointer-[GlobalKey#665ae] ← ⋯, parentData: <none> (can use size), constraints: BoxConstraints(w=411.4, 0.0<=h<=Infinity), size: MISSING, direction: vertical, mainAxisAlignment: start, mainAxisSize: max, crossAxisAlignment: center, verticalDirection: down)

I/flutter ( 4539): The creator information is set to:

I/flutter ( 4539):   Column ← RepaintBoundary ← IndexedSemantics ← NotificationListener<KeepAliveNotification> ←

I/flutter ( 4539):   KeepAlive ← AutomaticKeepAlive ← KeyedSubtree ← SliverList ← MediaQuery ← SliverPadding ←

I/flutter ( 4539):   ShrinkWrappingViewport ← IgnorePointer-[GlobalKey#665ae] ← ⋯

I/flutter ( 4539): See also: https://flutter.dev/layout/

I/flutter ( 4539): If none of the above helps enough to fix this problem, please don't hesitate to file a bug:

I/flutter ( 4539):   https://github.com/flutter/flutter/issues/new?template=BUG.md

I/flutter ( 4539): 

I/flutter ( 4539): The relevant error-causing widget was:

I/flutter ( 4539):   Column

In the second example, the screen turns white, but nothing happens and nothing works. At the first error the screen turns red and I get the error that you can see in the picture!

Red Error on the Screen

Answer 1

Using Of Expanded widget in listview is not valid because expanded widget doesn’t get any height to expand, so removing expanded widget solve your issue.

Answer 2

I/flutter ( 4539): RenderFlex children have non-zero flex but incoming height constraints are unbounded.

I/flutter ( 4539): When a column is in a parent that does not provide a finite height constraint, for example if it is

I cant' see the complete code for now, but what this means for you is, that your listview needs a kind of height which is give for example if you wrap it inside a container.

Second thing you can do is put shrinkwrap: true in listview

import 'package:flutter/material.dart';

void main() => runApp(App());

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(),
        body: Center(
          child: Container(
            margin: EdgeInsets.all(32),
            decoration: BoxDecoration(border: Border.all(color: Colors.red)),
            child: ListView(
              shrinkWrap: true,
              children: <Widget>[
                ListTile(title: Text('Item 1')),
                ListTile(title: Text('Item 2')),
                ListTile(title: Text('Item 3')),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

your listview then only takes the height of all your widgets or items inside the listview itself.

Hope it helps.