[material_ui] Add enabled parameter to DropdownButtonFormField by Mairramer · Pull Request #12610 · flutter/packages

Mairramer · 2026-08-25T12:42:01Z

Introduced the enabled parameter in DropdownButtonFormField, allowing proper disabled/read-only usage without needing to pass dummy callbacks or remove existing ones.

Previously, the only way to disable a DropdownButtonFormField was to set onChanged: null. With this change, developers can explicitly control the interactive state via the enabled property. For example, you can set enabled: false while keeping onChanged defined, or set enabled: true to have an interactive field even if onChanged is omitted.

This change is fully backward compatible. If the enabled property is omitted (left as null), the field will fall back to the legacy behavior: it will be enabled if and only if onChanged is non-null.

Closes flutter/flutter#57953.

Port of flutter/flutter#182419.

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…n and DropdownButtonFormField

…for fallback behavior

# Conflicts: # packages/material_ui/lib/src/dropdown.dart

gemini-code-assist

Code Review

This pull request makes the onChanged parameter optional and introduces an enabled property to both DropdownButton and DropdownButtonFormField to control their interactivity, along with corresponding updates to documentation, migration fixes, and tests. Feedback on the changes highlights a critical issue in DropdownButtonFormField where providing enabled: true with a null onChanged callback prevents the form field's value from updating when an item is selected. To resolve this, it is recommended to pass state.didChange to the underlying DropdownButton whenever the form field is enabled, and to add a test case verifying this behavior.

gemini-code-assist · 2026-10-01T19:03:41Z

                 barrierDismissible: barrierDismissible,
                 mouseCursor: mouseCursor,
                 dropdownMenuItemMouseCursor: dropdownMenuItemMouseCursor,
+                 enabled: isDropdownEnabled,


There is a critical bug here when DropdownButtonFormField is used with onChanged: null (or not provided) and enabled: true.\n\nIn the DropdownButtonFormField builder, the onChanged argument passed to DropdownButton is likely still defined as:\ndart\nonChanged: onChanged == null ? null : state.didChange,\n\nIf onChanged is null, this evaluates to null, so DropdownButton receives onChanged: null. Even though enabled: isDropdownEnabled (which is true) is passed to DropdownButton, making it interactive, selecting an item will do nothing because its onChanged callback is null. As a result, state.didChange is never called, and the form field's value is never updated.\n\nTo fix this, the onChanged argument passed to DropdownButton inside the builder should be updated to:\ndart\nonChanged: field.widget.enabled ? state.didChange : null,\n\nThis ensures that state.didChange is always called when the dropdown is enabled, which in turn updates the form field's value and safely calls the optional widget.onChanged callback if it is provided.

gemini-code-assist · 2026-10-01T19:03:41Z

              );
            }).toList(),
            alignment: buttonAlignment,
+            enabled: enabled,


Please add a test case to verify that DropdownButtonFormField works correctly when onChanged is null but enabled is true.\n\nSpecifically, the test should assert that:\n1. The dropdown is enabled and interactive.\n2. Selecting an item successfully updates the form field's value (i.e., formFieldKey.currentState.value changes to the selected item).\n\nThis will help prevent regressions and ensure that the new feature (making onChanged optional for read-only/disabled form field usage) works as intended.

QuncCccccc · 2026-10-06T21:34:19Z

[from triage] Could you help fix the conflict:)?

# Conflicts: # packages/material_ui/lib/src/dropdown.dart

dkwingsmt

Additionally, I suggest adding a constructor assertion assert(enabled != true || onChanged != null), because in such cases the DropdownButton can be opened but any selection is dropped (since the button doesn't save its own values).

dkwingsmt · 2026-10-09T22:32:52Z

    this.isVerticallyExpanded = false,
    required this._inputDecoration,
    required this._isEmpty,
+    bool? enabled,


Why is this new parameter not used in the constructor's only invocation at L1966?

IMO DropdownButtonFormField should pass down enabled and set onChanged as isDropdownEnabled ? state.didChange : null.

dkwingsmt · 2026-10-09T22:34:38Z

+  DropdownButtonFormField(onChanged: (String? v) {});
+
+  // Changes made in https://github.com/flutter/flutter/pull/182419.
+  DropdownButton(onChanged: null, enabled: true);


These look like strange cases here because enabled did not even exist before this PR.

In fact, at the current changes I suspect that this PR is no longer breaking and should not need a dartfix.

dkwingsmt · 2026-10-09T22:44:44Z

    // When adding new arguments, consider adding similar arguments to
    // DropdownButtonFormField.
-  }) : assert(
+  }) : enabled = enabled ?? onChanged != null,


I suggest keeping enabled as bool?. While technically Dart allows constructor's arguments to be independent of the getters, it has been a convention of Flutter that they're identical and making them different like this will be confusing. Considering that getters of widgets are rarely used I think it's ok to just keep it the simple way.

dkwingsmt · 2026-10-09T22:47:53Z

  /// If this property is null, [WidgetStateMouseCursor.adaptiveClickable] will be used.
  final MouseCursor? dropdownMenuItemMouseCursor;

+  /// Whether the [DropdownButton] is enabled.


This doc should also be updated to reflect the functionality of the bool? enabled parameter, not the calculated bool enabled effective value.

dkwingsmt · 2026-10-09T23:33:54Z

Update: after thinking about this more, this comment replaces my earlier inline comments about DropdownButton.enabled (keeping it bool?, its docs, and the assert). I now think DropdownButton doesn't need a new parameter at all. My comment on L1086 still applies in spirit, but the fix is different from what it implied (see below).

I think most of the issues here come from mixing up two layers that handle "enabled" differently. It might help to look at each one separately.

Layer 1: DropdownButton

DropdownButton doesn't store a value. The parent passes value in, and onChanged is the only way a selection gets back out. So for this widget, onChanged is the output channel, not just a notification, and "enabled iff onChanged != null" is the right rule. Checkbox, Switch and Slider follow the same rule.

An enabled parameter doesn't fit well here:

enabled: true either repeats what onChanged != null already says, or creates a dropdown that opens but drops every selection.
Only enabled: false adds anything, and that is the same as writing onChanged: disabled ? null : callback.

The issue (flutter/flutter#57953) also only asks about the form field. So I'd suggest reverting the DropdownButton changes, including the new parameter on _formField. If there's demand for DropdownButton.enabled, it can be discussed separately.

Layer 2: DropdownButtonFormField

The form field does store the value, in FormFieldState. The user's onChanged is only an optional notification on top of that, like in TextFormField. This is the layer the issue is about: users want an enabled field without passing a dummy onChanged.

The form field can get there without any help from DropdownButton. Whenever the field is enabled, it gives the inner button its own output channel, state.didChange, and didChange already calls the user's onChanged if one was provided. Whether the user passed onChanged should only affect the fallback when enabled is null, not how the inner button is wired:

super(
  // FormField.enabled also controls validation. Only an explicit
  // `enabled: false` should turn validation off, so existing
  // `onChanged: null` fields keep validating like they do today.
  enabled: enabled ?? true,
  builder: (FormFieldState<T> field) {
    final bool isDropdownEnabled =
        (enabled ?? onChanged != null) && items != null && items.isNotEmpty;
    // ...
    DropdownButton<T>._formField(
      onChanged: isDropdownEnabled ? state.didChange : null,
      // ...
    );
  },
);

Compared to this, the current PR has three problems:

L1972 still passes onChanged == null ? null : state.didChange, so enabled: true without onChanged (the case the issue asks for) shows an enabled decoration but leaves the button disabled.
With enabled: false and an onChanged, the decoration and FormField are disabled, but the inner button is still interactive.
super(enabled: enabled ?? onChanged != null) turns off autovalidation for every existing onChanged: null field, which is a behavior change the PR doesn't mention.

About the constructor parameter and the getter: FormField already declares final bool enabled, and Dart doesn't allow a subclass to override it with bool?. The parameter can't be a non-nullable bool enabled = true either. It couldn't tell "not passed" apart from true, so it would either break existing onChanged: null fields or still require onChanged. So, like TextFormField, the constructor should take bool? enabled and pass the resolved value to super.enabled. The raw argument is still available in the builder closure, the same way onChanged and items are.

What this means for the rest of the PR

With enabled: null falling back to the old rule, this change is purely additive:

The "Breaking change" section in the description doesn't apply and can be removed.
The dart fix rules and test_fixes can be removed. The rule for onChanged: null, enabled: true would also have rewritten it to enabled: false.
The onChanged doc template can go back to its original wording. A doc comment on the new enabled should explain the fallback.
For tests:
- Revert the changes to existing tests (including passing enabled to DropdownMenuItem in the buildDropdown helper). As they were, they cover the fallback path.
- Add form-field tests for the new combinations: enabled: true without onChanged updates FormFieldState.value when an item is selected, and enabled: false with onChanged doesn't open the menu.
- Add one more test that an onChanged: null field still autovalidates.

dkwingsmt

(Forgot to post my comments regarding the changelog)

dkwingsmt · 2026-10-12T18:14:13Z

I'd also suggest adding the following sentence to the end of onChanged's doc:
  /// If the constructor's `enabled` argument is true, the field is interactive even
  /// when [onChanged] is null.

Just a reminder that this hasn't been addressed. Otherwise the code LGTM.

…638061467.yaml Co-authored-by: Tong Mu <[email protected]>

dkwingsmt

LGTM

QuncCccccc

LGTM. Thank you:)

QuncCccccc

LGTM. Thank you:)!

Co-authored-by: Qun Cheng <[email protected]>

Roll Packages from a1ed23c to da40eaf (33 revisions) flutter/packages@a1ed23c...da40eaf 2026-10-15 [email protected] [pigeon]add support for sealed classes in native interop (flutter/packages#13175) 2026-10-15 [email protected] [pigeon] Replace full JNI bindings with stubs for API classes that aren't needed (flutter/packages#13173) 2026-10-14 [email protected] [material_ui] Fix self-comparison and assert bugs in semantics_tester (flutter/packages#12722) 2026-10-14 [email protected] [camera_avfoundation] Replace the deprecated 'videoOrientation' with 'videoRotationAngle' on iOS 17+ (flutter/packages#13247) 2026-10-14 [email protected] [material_ui] Fix GridTile crash when the incoming constraints are unbounded (flutter/packages#12586) 2026-10-14 [email protected] [in_app_purchase_storekit] Remove unused and deprecated "SKDownload" hosted content (flutter/packages#13222) 2026-10-14 [email protected] [material_ui] Add supportingTextPadding to InputDecorator (flutter/packages#12769) 2026-10-14 [email protected] [vector_graphics_codec] Add support for encoding and decoding paint blur commands (flutter/packages#13148) 2026-10-14 [email protected] [go_router] Fix redirect zone async error handling (flutter/packages#12836) 2026-10-14 [email protected] Sync release-go_router-18.1.0 to main (flutter/packages#13260) 2026-10-14 [email protected] Sync release-cupertino_ui-1.1.3 to main (flutter/packages#13258) 2026-10-14 [email protected] [material_ui] add enableInlinePrediction parameter to TextFormField (flutter/packages#12793) 2026-10-14 [email protected] Sync release-material_ui-1.7.0 to main (flutter/packages#13259) 2026-10-14 [email protected] [material_ui] Add the Material shapes. (flutter/packages#12771) 2026-10-14 [email protected] [material_ui] Add tertiary tap callbacks to InkResponse and InkWell (flutter/packages#12676) 2026-10-14 [email protected] Roll Flutter from 4249ccb to 426be96 (44 revisions) (flutter/packages#13256) 2026-10-14 [email protected] [material_ui] fixes expanded state in the a11y_assessment home page dropdown (flutter/packages#13219) 2026-10-14 [email protected] [VPAT] Fix semantics in a11y_assessments drawer, radio, and rail demos (flutter/packages#13159) 2026-10-14 [email protected] [google_maps_flutter] Add onPointOfInterestTap (flutter/packages#11872) 2026-10-14 [email protected] [go_router] Fix shell route key collisions and dynamic branch updates (flutter/packages#12549) 2026-10-14 [email protected] Manual roll Flutter from d03768e to 4249ccb (158 revisions) (flutter/packages#13220) 2026-10-14 [email protected] [image_picker_ios] Require Flutter 3.47 / iOS 15 and drop deprecated kUTType code paths (flutter/packages#13224) 2026-10-13 [email protected] [in_app_purchase_storekit] Fixes Storekit 2 flaky tests (flutter/packages#13213) 2026-10-13 [email protected] [local_auth] Convert Android to new Pigeon suspend support (flutter/packages#12894) 2026-10-13 [email protected] [material_ui] Add enabled parameter to DropdownButtonFormField (flutter/packages#12610) 2026-10-13 [email protected] [go_router] Link ShellRoute docs to StatefulShellRoute (flutter/packages#13120) 2026-10-13 [email protected] FadeForwards page transition performance (flutter/packages#13161) 2026-10-13 [email protected] [in_app_purchase_android] Guard async billing callbacks against duplicate listener responses (flutter/packages#12640) 2026-10-13 [email protected] [google_sign_in] Remove the Objective-C exception catcher (flutter/packages#13156) 2026-10-13 [email protected] [camera_avfoundation] Remove availability checks below the package minimum iOS 13 (flutter/packages#13214) 2026-10-13 [email protected] [google_maps_flutter_ios] Remove iOS 14 availability check from example UI tests (flutter/packages#13218) 2026-10-13 [email protected] [google_sign_in] Convert implementation to Kotlin (flutter/packages#13005) 2026-10-13 [email protected] [image_picker_ios] PR 2/5 Add a PHImageManager image-data seam and migrate plugin native tests to Swift Testing (flutter/packages#13079) If this roll has caused a breakage, revert this CL and set the roller to dry run mode using the controls here: https://autoroll.skia.org/r/flutter-packages-flutter-autoroll Please CC [email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: ...

Mairramer added 11 commits August 25, 2026 09:37

Make 'onChanged' optional and add 'enabled' property to DropdownButto…

952dfd3

…n and DropdownButtonFormField

fix tests

7c6490f

fix web tests

2c60aa6

improve docs

45a97e2

add fix

d6e535b

improve fix_data

048ccc5

fix some migrations

553a2e8

fix docs

1d481a2

refactor: update DropdownButton enabled property logic and add tests …

9f5f5a1

…for fallback behavior

Update DropdownButton documentation to clarify enabled property behavior

cc3e722

chore: add changelog for DropdownButton enabled property

5453d20

github-actions Bot added p: material_ui triage-design Should be looked at in design triage labels Aug 25, 2026

Mairramer mentioned this pull request Aug 25, 2026

Make onChanged optional and add enabled to DropdownButtonFormField flutter/flutter#182419

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Mairramer added 2 commits October 1, 2026 09:02

Merge branch 'main' into feature/remove-required-onchanged

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# Conflicts: # packages/material_ui/lib/src/dropdown.dart

fix(dropdown): remove redundant enabled parameter initialization

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update DropdownButton fix URIs

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Merge branch 'main' into feature/remove-required-onchanged

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# Conflicts: # packages/material_ui/lib/src/dropdown.dart

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refactor: remove enabled property from DropdownButton

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Comment thread packages/material_ui/pending_changelogs/change_2026_10_10_1791638061467.yaml Resolved

Comment thread packages/material_ui/pending_changelogs/change_2026_10_10_1791638061467.yaml Resolved

Update packages/material_ui/pending_changelogs/change_2026_10_10_1791…

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…638061467.yaml Co-authored-by: Tong Mu <[email protected]>

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Mairramer and others added 2 commits October 12, 2026 15:51

fix some nits

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Merge branch 'main' into feature/remove-required-onchanged

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Comment thread packages/material_ui/lib/src/dropdown.dart Resolved

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Merge branch 'main' into feature/remove-required-onchanged

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Fix formatting in DropdownButtonFormField documentation

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Roll Packages from a1ed23c8f760 to ac2db9cfeaf6 (12 revisions) flutter/flutter#194387

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Roll Packages from a1ed23c8f760 to da40eaf4548a (33 revisions) flutter/flutter#194459

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JannikWinter mentioned this pull request Oct 23, 2026

[material_ui] DropdownButtonFormField: InputDecoration looks enabled and reacts to hover when enabled: false flutter/flutter#195192

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