Extending border and using it in animated scenarios throws exception #180297

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1. tirth-patel-nc

   added

   in triagePresently being triaged by the triage teamPresently being triaged by the triage team

   on Jan 2, 2026
2. tirth-patel-nc commented on Jan 2, 2026

   

   tirth-patel-nc

   on Jan 2, 2026

   Last edited by tirth-patel-nc

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   Thanks for the report. Seeing the same behaviour with latest SDK versions.

   stable : 3.38.5
   master : 3.40.0-1.0.pre-369
   
3. tirth-patel-nc

   added

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

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

   a: error messageError messages from the Flutter frameworkError messages from the Flutter framework

   has reproducible stepsThe issue has been confirmed reproducible and is ready to work onThe issue has been confirmed reproducible and is ready to work on

   found in release: 3.38Found to occur in 3.38Found to occur in 3.38

   found in release: 3.40Found to occur in 3.40Found to occur in 3.40

   a: animationAnimation APIsAnimation APIs

   team-frameworkOwned by Framework teamOwned by Framework team

   and removed

   in triagePresently being triaged by the triage teamPresently being triaged by the triage team

   on Jan 2, 2026
4. justinmc

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

   triaged-frameworkTriaged by Framework teamTriaged by Framework team

   on Jan 14, 2026
5. justinmc commented on Jan 14, 2026

   

   justinmc

   on Jan 14, 2026

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   @obiwanzenobi Can you paste in a runnable repro of this?
6. obiwanzenobi commented on Jan 14, 2026

   

   obiwanzenobi

   on Jan 14, 2026

   Last edited by obiwanzenobi

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   @obiwanzenobi Can you paste in a runnable repro of this?

   Yes, I will put single file repro tomorrow - in the meantime you can check repository attached in the issue - which has runnable reproduction scenario
7. marejonc commented on Mar 9, 2026

   

   marejonc

   on Mar 9, 2026

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   @justinmc Here is a condensed repro

   import 'package:flutter/material.dart';
   
   void main() {
     runApp(const MyApp());
   }
   
   class MyApp extends StatelessWidget {
     const MyApp({super.key});
   
     // This widget is the root of your application.
     @override
     Widget build(BuildContext context) {
       return MaterialApp(
         debugShowCheckedModeBanner: false,
         title: 'Flutter Demo',
         theme: ThemeData(primarySwatch: Colors.blue),
         home: const MyHomePage(),
       );
     }
   }
   
   class MyHomePage extends StatefulWidget {
     const MyHomePage({super.key});
   
     @override
     State<MyHomePage> createState() => _MyHomePageState();
   }
   
   class _MyHomePageState extends State<MyHomePage> {
     bool _shouldShowSecondState = false;
   
     @override
     Widget build(BuildContext context) {
       return Scaffold(
         appBar: AppBar(
           title: const Text("Gradient borders"),
           actions: [
             IconButton(
               icon: const Icon(Icons.refresh),
               onPressed: () {
                 setState(() {
                   _shouldShowSecondState = !_shouldShowSecondState;
                 });
               },
             ),
           ],
         ),
         body: Center(
           child: AnimatedContainer(
             duration: const Duration(milliseconds: 500),
             width: 100,
             height: 100,
             decoration: BoxDecoration(
               border: GradientBoxBorder(
                 gradient: _shouldShowSecondState
                     ? LinearGradient(colors: [Colors.green, Colors.pink])
                     : LinearGradient(colors: [Colors.blue, Colors.red]),
                 width: 4,
               ),
               borderRadius: BorderRadius.circular(16),
             ),
           ),
         ),
       );
     }
   }
   
   class GradientBoxBorder extends BoxBorder {
     const GradientBoxBorder({required this.gradient, this.width = 1.0});
   
     final Gradient gradient;
     final double width;
   
     @override
     BorderSide get bottom => BorderSide.none;
   
     @override
     BorderSide get top => BorderSide.none;
   
     @override
     EdgeInsetsGeometry get dimensions => EdgeInsets.all(width);
   
     @override
     bool get isUniform => true;
   
     @override
     void paint(
       Canvas canvas,
       Rect rect, {
       TextDirection? textDirection,
       BoxShape shape = BoxShape.rectangle,
       BorderRadius? borderRadius,
     }) {
       switch (shape) {
         case BoxShape.circle:
           assert(
             borderRadius == null,
             'A borderRadius can only be given for rectangular boxes.',
           );
           _paintCircle(canvas, rect);
           break;
         case BoxShape.rectangle:
           if (borderRadius != null) {
             _paintRRect(canvas, rect, borderRadius);
             return;
           }
           _paintRect(canvas, rect);
           break;
       }
     }
   
     void _paintRect(Canvas canvas, Rect rect) {
       canvas.drawRect(rect.deflate(width / 2), _getPaint(rect));
     }
   
     void _paintRRect(Canvas canvas, Rect rect, BorderRadius borderRadius) {
       final rrect = borderRadius.toRRect(rect).deflate(width / 2);
       canvas.drawRRect(rrect, _getPaint(rect));
     }
   
     void _paintCircle(Canvas canvas, Rect rect) {
       final paint = _getPaint(rect);
       final radius = (rect.shortestSide - width) / 2.0;
       canvas.drawCircle(rect.center, radius, paint);
     }
   
     @override
     ShapeBorder scale(double t) {
       return this;
     }
   
     Paint _getPaint(Rect rect) {
       return Paint()
         ..strokeWidth = width
         ..shader = gradient.createShader(rect)
         ..style = PaintingStyle.stroke;
     }
   }
   

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8. auto-submit

   closed this as completedin #186348on Jul 21, 2026
9. srawlins

   added a commit that references this issue on Jul 21, 2026

   Support custom BoxBorder animation in BoxDecoration (flutter#186348)

   ...

   6ebcc81
10. github-actions commented on Aug 5, 2026

    

    github-actionsbot

    on Aug 5, 2026 – with GitHub Actions

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    This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.
11. github-actions

    locked as resolved and limited conversation to collaborators on Aug 5, 2026