Flutter RenderFlex Error: Children have non-zero flex but incoming width constraints are unbounded

FarisA
March 15, 2024
90 views
0 votes
2 Answers

I’m here encountering a renderflex issue with my Flutter app. I’m struggling to understand what’s the problem. Error Here’s the error that I’m encountering https://phpout.com/wp-content/uploads/2024/03/kyn4J.png.

Exception has occurred.
FlutterError (RenderFlex children have non-zero flex but incoming width constraints are unbounded.
When a row is in a parent that does not provide a finite width constraint, for example if it is in a horizontal scrollable, it will try to shrink-wrap its children along the horizontal axis. Setting a flex on a child (e.g. using Expanded) indicates that the child is to expand to fill the remaining space in the horizontal direction.
These two directives are mutually exclusive. If a parent is to shrink-wrap its child, the child cannot simultaneously expand to fit its parent.
Consider setting mainAxisSize to MainAxisSize.min and using FlexFit.loose fits for the flexible children (using Flexible rather than Expanded). This will allow the flexible children to size themselves to less than the infinite remaining space they would otherwise be forced to take, and then will cause the RenderFlex to shrink-wrap the children rather than expanding to fit the maximum constraints provided by the parent.
If this message did not help you determine the problem, consider using debugDumpRenderTree():
  https://flutter.dev/debugging/#rendering-layer
  http://api.flutter.dev/flutter/rendering/debugDumpRenderTree.html
The affected RenderFlex is:
  RenderFlex#d991e relayoutBoundary=up13 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE(creator: Row ← Padding ← Container ← DefaultTextStyle ← Stack ← Listener ← RawGestureDetector ← GestureDetector ← Semantics ← DefaultSelectionStyle ← Builder ← MouseRegion ← ⋯, parentData: offset=Offset(0.0, 0.0) (can use size), constraints: BoxConstraints(unconstrained), size: MISSING, direction: horizontal, mainAxisAlignment: spaceBetween, mainAxisSize: min, crossAxisAlignment: center, textDirection: ltr, verticalDirection: down)
The creator information is set to:
  Row ← Padding ← Container ← DefaultTextStyle ← Stack ← Listener ← RawGestureDetector ← GestureDetector ← Semantics ← DefaultSelectionStyle ← Builder ← MouseRegion ← ⋯
The nearest ancestor providing an unbounded width constraint is: RenderFlex#903bb relayoutBoundary=up4 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE:
  creator: Row ← Padding ← Column ← Padding ← KeyedSubtree-[GlobalKey#9b537] ← _BodyBuilder ← MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ← _ActionsScope ← Actions ← AnimatedBuilder ← ⋯
  parentData: offset=Offset(0.0, 0.0) (can use size)
  constraints: BoxConstraints(0.0<=w<=1240.0, 0.0<=h<=Infinity)
  size: MISSING
  direction: horizontal
  mainAxisAlignment: start
  mainAxisSize: max
  crossAxisAlignment: center
  textDirection: ltr
  verticalDirection: down
See also: https://flutter.dev/unbounded-constraints
If none of the above helps enough to fix this problem, please don't hesitate to file a bug:
  https://github.com/flutter/flutter/issues/new?template=2_bug.yml)

And this is the code of the file

import 'package:flutter/material.dart';

class DueDateCalculator extends StatelessWidget {
  const DueDateCalculator({super.key});

  @override
  Widget build(BuildContext context) {
    String dropdownValue = 'Last Period';
    return Scaffold(
      appBar: AppBar(title: const Text('Due Date Calculator')),
      body: Padding(
        padding: const EdgeInsets.only(left: 16.0),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.start,
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            const SizedBox(
              height: 140,
            ),
            const Center(
              child: Text(
                'Due Date Calculator',
                textAlign: TextAlign.center,
                style: TextStyle(fontSize: 22, fontWeight: FontWeight.bold),
              ),
            ),
            const SizedBox(
              height: 10,
            ),
            const Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Expanded(
                  child: Text(
                    'Choose from various methods for due date prediction.',
                    textAlign: TextAlign.center,
                    style: TextStyle(),
                  ),
                ),
              ],
            ),
            const SizedBox(
              height: 40,
            ),
            Padding(
              padding: const EdgeInsets.only(left: 8.0),
              child: Row(
                children: [
                  const Text(
                    'Method',
                    style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
                  ),
                  const SizedBox(
                    width: 100,
                  ),
                  Padding(
                    padding: const EdgeInsets.only(right: 8.0),
                    child: DropdownButton<String>(
                      isExpanded: true,
                      underline: Container(),
                      value: dropdownValue,
                      items: <String>[
                        'Last Period',
                        'Conception Date',
                        'IVF',
                        'Method 4'
                      ].map((String value) {
                        return DropdownMenuItem<String>(
                          value: value,
                          child: Text(value),
                        );
                      }).toList(),
                      onChanged: (String? newValue) {
                        // Handle dropdown selection
                      },
                    ),
                  ),
                ],
              ),
            ),
            const SizedBox(
              height: 10,
            ),
            const Divider(
              color: Colors.grey,
              height: 10,
              thickness: 0.5,
              indent: 2,
              endIndent: 10,
            ),
          ],
        ),
      ),
    );
  }
}

I searched it on ChatGpt and on google but couldn’t really find a solution.

Answers

You need to wrap the dropdown with an Expanded widget as you have wrapped it with a Row which has infinite width, also the dropdown widget uses Row inside which is getting infinite width here.

Expanded(
  child: Padding(
    padding: const EdgeInsets.only(right: 8.0),
    child: DropdownButton<String>(
      isExpanded: true,
      underline: Container(),
      value: dropdownValue,
      items: <String>[
        'Last Period',
        'Conception Date',
        'IVF',
        'Method 4'
      ].map((String value) {
        return DropdownMenuItem<String>(
          value: value,
          child: Text(value),
        );
      }).toList(),
      onChanged: (String? newValue) {
        // Handle dropdown selection
      },
    ),
  ),
),

The error you are getting is due to the DropDownButton. To solve it either wrap it with Expanded widget to take all the available width like this:

Expanded(
    child: Padding(
      padding: const EdgeInsets.only(right: 8.0),
      child: DropdownButton<String>(
        isExpanded: true,
        underline: Container(),
        value: dropdownValue,
        items: <String>['Last Period', 'Conception Date', 'IVF', 'Method 4']
            .map((String value) {
          return DropdownMenuItem<String>(
            value: value,
            child: Text(value),
          );
        }).toList(),
        onChanged: (String? newValue) {
          // Handle dropdown selection
        },
      ),
    ),
  )

or wrap it with Container/SizedBox and give desired width to it like this:

Container(
    width: 200,
    padding: const EdgeInsets.only(right: 8.0),
    child: DropdownButton<String>(
      isExpanded: true,
      underline: Container(),
      value: dropdownValue,
      items: <String>['Last Period', 'Conception Date', 'IVF', 'Method 4']
          .map((String value) {
        return DropdownMenuItem<String>(
          value: value,
          child: Text(value),
        );
      }).toList(),
      onChanged: (String? newValue) {
        // Handle dropdown selection
      },
    ),
  )

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