Wrap widget in flutter with a min size for children, expanded otherwise

The flex_list package may be used here with some modifications.

The FlexList will space each element just like a wrap might, but will then expand each element to completely fill up a row. The caveat here is that each element needs to implement a computeDryLayout method, which a TextField does not.

A workaround to this is to wrap each TextField in a render object that use the child's intrinsic dimensions instead of invoking the child's dry layout method. see this github issue for a discussion around the topic.

the object we need to wrap each text field may be added to the project like so:

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

/// NOTE ref: https://github.com/flutter/flutter/issues/71687 & https://gist.github.com/matthew-carroll/65411529a5fafa1b527a25b7130187c6
/// Same as `IntrinsicWidth` except that when this widget is instructed
/// to `computeDryLayout()`, it doesn't invoke that on its child, instead
/// it computes the child's intrinsic width.
///
/// This widget is useful in situations where the `child` does not
/// support dry layout, e.g., `TextField` as of 01/02/2021.
class DryIntrinsicWidth extends SingleChildRenderObjectWidget {
  const DryIntrinsicWidth({Key? key, Widget? child}) : super(key: key, child: child);

  @override
  RenderDryIntrinsicWidth createRenderObject(BuildContext context) => RenderDryIntrinsicWidth();
}

class RenderDryIntrinsicWidth extends RenderIntrinsicWidth {
  @override
  Size computeDryLayout(BoxConstraints constraints) {
    if (child != null) {
      final width = child!.computeMinIntrinsicWidth(constraints.maxHeight);
      final height = child!.computeMinIntrinsicHeight(width);
      return Size(width, height);
    } else {
      return Size.zero;
    }
  }
}

/// NOTE ref: https://github.com/flutter/flutter/issues/71687 & https://gist.github.com/matthew-carroll/65411529a5fafa1b527a25b7130187c6
/// Same as `IntrinsicHeight` except that when this widget is instructed
/// to `computeDryLayout()`, it doesn't invoke that on its child, instead
/// it computes the child's intrinsic height.
///
/// This widget is useful in situations where the `child` does not
/// support dry layout, e.g., `TextField` as of 01/02/2021.
class DryIntrinsicHeight extends SingleChildRenderObjectWidget {
  const DryIntrinsicHeight({Key? key, Widget? child}) : super(key: key, child: child);

  @override
  RenderDryIntrinsicHeight createRenderObject(BuildContext context) => RenderDryIntrinsicHeight();
}

class RenderDryIntrinsicHeight extends RenderIntrinsicHeight {
  @override
  Size computeDryLayout(BoxConstraints constraints) {
    if (child != null) {
      final height = child!.computeMinIntrinsicHeight(constraints.maxWidth);
      final width = child!.computeMinIntrinsicWidth(height);
      return Size(width, height);
    } else {
      return Size.zero;
    }
  }
}

Now with these new objects we can use the same given list like below. Instead of a flex factor, the width of each SizedBox may be used to make it behave similar to a flex on an Expanded object.

(e.x. width of 200 and 400 would be like a flex of 1 and 2)

FlexList(
            verticalSpacing: 0,
            horizontalSpacing: 4,
            children: [
              DryIntrinsicWidth(
                child: SizedBox(
                  width: 400,
                  child: createTextField(
                    context,
                    'Ref. Company (Insurer)',
                    'reference_company',
                    initialValue: widget.form.referenceCompany ?? '',
                    onChange: (val) => widget.form.referenceCompany = val,
                    enabled: bo.insurerInfo.insurer.isNullOrEmpty(),
                  ),
                ),
              ),
              DryIntrinsicWidth(
                child: SizedBox(
                  width: 200,
                  child: createTextField(
                    context,
                    'Community Id',
                    'community_id',
                    initialValue: widget.form.communityId ?? '',
                    onChange: (val) => widget.form.communityId = val,
                    // expanded: true,
                  ),
                ),
              ),
              DryIntrinsicWidth(
                child: SizedBox(
                  width: 200,
                  child: createTextField(
                    context,
                    'Community Name',
                    'community_name',
                    initialValue: widget.form.communityName ?? '',
                    onChange: (val) => widget.form.communityName = val,
                    // expanded: true,
                  ),
                ),
              ),
            ],
          ),

Note: The width on the SizedBox is treated like a minWidth and this will be expanded by the FlexList if more space is available.