Null check operator used on a null value on Switch _pressedThumbExtension #179532

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1. darshankawar

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   p: material_uimaterial_ui package in flutter/packagesmaterial_ui package in flutter/packages

   frameworkflutter/packages/flutter repository. See also f: labels.flutter/packages/flutter repository. See also f: labels.

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   on Dec 8, 2025
2. dkwingsmt commented on Dec 10, 2025

   

   dkwingsmt

   on Dec 10, 2025

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   It would be more helpful if you can provide a reproduction that triggers this crash. This issue can use such a production for future tracking, and your PR will certainly need this reproduction for regression test.
3. dkwingsmt

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   P2Important issues not at the top of the work listImportant issues not at the top of the work list

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   on Dec 10, 2025
4. ishaquehassan commented on Feb 27, 2026

   

   ishaquehassan

   on Feb 27, 2026

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   Looking at packages/flutter/lib/src/material/switch.dart, the crash comes from _pressedThumbExtension being declared as late double? (line 1507) but only assigned inside the if (!_stopPressAnimation) block (line 1526). When _stopPressAnimation is true (which happens when reaction.status == AnimationStatus.reverse on the very first paint call after a touch lifts), the field is never initialized.

   _computeThumbPaintOffset uses _pressedThumbExtension! unconditionally at lines 1720 and 1724, regardless of _stopPressAnimation. So on the first paint() with _stopPressAnimation = true, you get a LateInitializationError.

   The fix is to drop late and give the field a default value of 0 instead:

   // Before:
   late double? _pressedThumbExtension;
   
   // After:
   double _pressedThumbExtension = 0;

   Then remove the ! in _computeThumbPaintOffset (lines 1720, 1724), since the field is no longer nullable. The isCupertino paths at lines 1559, 1565, and 1616 that use _pressedThumbExtension! are already inside the if (!_stopPressAnimation) guard, so they just become plain _pressedThumbExtension after the type change.

   This guarantees the field always has a valid value before _computeThumbPaintOffset runs, regardless of animation state or frame timing.
5. Piinks

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   packageflutter/packages repository. See also p: labels.flutter/packages repository. See also p: labels.

   and removed

   frameworkflutter/packages/flutter repository. See also f: labels.flutter/packages/flutter repository. See also f: labels.

   on Aug 17, 2026
6. muralikrishmt

   self-assigned this

   on Oct 27, 2026
7. auto-submit

   closed this as completedin packages#13496on Nov 5, 2026
8. ksokolovskyi

   added a commit that references this issue on Nov 5, 2026

   [material_ui] Fix Switch throwing when first painted mid-animation (f…

   ...

   22027c5