[material_ui] Handle unknown swipe edges in predictive back transitions by muhammadkamel · Pull Request #12502 · flutter/packages

muhammadkamel · 2026-08-18T21:17:29Z

Ports the Material side of flutter/flutter#185140 after the Material/Cupertino decoupling.

PredictiveBackPageTransitionsBuilder now treats unknown or button-triggered swipe edges as a no-direction fallback, matching Android BackEvent.EDGE_NONE. _ is used instead of SwipeEdge.none because that enum value is not in the Flutter SDK this package currently compiles against; it also keeps the switch exhaustive when the SDK gains new SwipeEdge values.

Adds coverage for right-edge swipes and for button-triggered back events (Offset.zero + progress: 0.0), which handleStartBackGesture already filters via isButtonEvent.

The RangeError in PredictiveBackEvent.fromMap for swipeEdge: 2 still lives in flutter/services and is fixed in flutter/flutter#191306. That crash cannot be fixed in this package.

Fixes flutter/flutter#186168

Pre-Review Checklist

Treat unknown or button-triggered swipe edges as a no-direction fallback so the switch stays exhaustive when the Flutter SDK adds SwipeEdge values.

gemini-code-assist

Code Review

This pull request updates PredictiveBackPageTransitionsBuilder to treat unknown or button-triggered swipe edges as a no-direction fallback, and adds tests for right-edge swipes and button-triggered back events. The review feedback suggests simplifying the switch expression by removing the redundant SwipeEdge.left case, and using a more precise assertion in the tests to verify that the page shifts in the correct direction.

justinmc

Thanks for porting your PR so quickly!

There's a slight change in process for material_ui and cupertino_ui regarding the changelog and version: you'll have to create a pending changelog yaml file. See https://github.com/flutter/packages/blob/main/packages/material_ui/pending_changelogs/template.yaml

Otherwise this looks good.

navaronbracke · 2026-08-23T21:41:11Z

+      await tester.tap(find.text('push'));
+      await tester.pumpAndSettle();
+
+      if (defaultTargetPlatform != TargetPlatform.android) {


Should this not be the skip and/or the variant argument of the test itself? For non Android, this test does setup and then no asserts, which reads a bit weird.

@muhammadkamel Maybe this was missed earlier, but you did not provide a reasoning for adding this return, over using a test variant or test skip?

navaronbracke · 2026-08-23T21:45:43Z

+    await tester.tap(find.text('push'));
+    await tester.pumpAndSettle();
+
+    if (defaultTargetPlatform != TargetPlatform.android) {


Same remark here

…e edge

muhammadkamel · 2026-08-29T15:04:02Z

Thanks for the review @justinmc and @navaronbracke! All comments have been addressed, please take another look.

elliette · 2026-09-29T22:18:11Z

[from triage] friendly ping @justinmc @navaronbracke are you still reviewing this PR? Thanks!

navaronbracke

While the overall change SGTM, I did have an open question (from my last review), relating to the use of a return to skip part of the test.

I think it would be better if the tests could be split into an Android version (which uses the full test) and a non-Android version (which uses the part up to the returns in the test body)

navaronbracke · 2026-09-30T06:21:34Z

+      await tester.tap(find.text('push'));
+      await tester.pumpAndSettle();
+
+      if (defaultTargetPlatform != TargetPlatform.android) {


@muhammadkamel Maybe this was missed earlier, but you did not provide a reasoning for adding this return, over using a test variant or test skip?

Replace the early return on non-Android platforms with TargetPlatformVariant.only(TargetPlatform.android), so the tests only run where they make assertions.

camle83it · 2026-10-05T01:34:30Z

Dear @muhammadkamel @navaronbracke
Thank you for your work on this PR and for taking the time to address this issue.
If possible, could you please continue supporting this PR and help move it forward until the issue is fully resolved?

elliette · 2026-10-27T21:26:50Z

cc @justinmc are you still reviewing this PR or would you like the ecosystem team to take over review? Thanks!

muhammadkamel · 2026-11-01T05:23:43Z

Hi @elliette, I think @justinmc is on an extended vacation. Could we assign another reviewer to help get this PR merged soon?

justinmc

Sorry I was traveling last week but back now. This looks good but I want to make sure adding a value to SwipeEdge is the right approach here, see my comment on that below.

justinmc · 2026-11-02T20:29:29Z

+          // `_` keeps the switch exhaustive if additional SwipeEdge values
+          // are added in the Flutter SDK.


@chunhtai I wonder what you think about this given that your RFC flutter/rfc#32 recommends against adding values to enums (see the framework side of this PR in flutter/flutter#185140). Should we migrate to a class-based SwipeEdge, or should we work with what we have for now?

this should stay an enum as it is closed by design (at most four directions)

unless Android start to support micro direction like bottom-left top-left. I doubt that will happen though, better not over-engineering now.

justinmc · 2026-11-02T20:29:37Z

+    variant: TargetPlatformVariant.only(TargetPlatform.android),
+  );
+
+  testWidgets('button-triggered back does not start a predictive back animation', (


Nit: Maybe change this to say "system button triggered", since you are talking about Android's system back button, right? To disambiguate it with a Flutter button.

justinmc

Ok this LGTM then based on @chunhtai 's response. 👍

[material_ui] Handle unknown swipe edges in predictive back transitions

4af88aa

Treat unknown or button-triggered swipe edges as a no-direction fallback so the switch stays exhaustive when the Flutter SDK adds SwipeEdge values.

gemini-code-assist Bot reviewed Aug 18, 2026

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

Comment thread packages/material_ui/test/predictive_back_page_transitions_builder_test.dart Resolved

github-actions Bot added triage-framework Should be looked at in framework triage p: material_ui labels Aug 18, 2026

dkwingsmt requested review from justinmc and navaronbracke August 19, 2026 18:33

justinmc reviewed Aug 20, 2026

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

navaronbracke requested changes Aug 23, 2026

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Merge branch 'main' into fix/material-ui-predictive-back-swipe-edge

0c04222

github-actions Bot added the triage-design Should be looked at in design triage label Aug 29, 2026

[material_ui] Address review comments on predictive back unknown swip…

aa7713e

…e edge

muhammadkamel requested review from justinmc and navaronbracke August 29, 2026 15:02

navaronbracke requested changes Sep 30, 2026

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muhammadkamel added 2 commits October 1, 2026 23:48

[material_ui] Use Android-only variant for new predictive back tests

b898d18

Replace the early return on non-Android platforms with TargetPlatformVariant.only(TargetPlatform.android), so the tests only run where they make assertions.

Merge branch 'main' into fix/material-ui-predictive-back-swipe-edge

62f5af4

navaronbracke approved these changes Oct 5, 2026

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navaronbracke added the CICD Run CI/CD label Oct 5, 2026

maRci002 mentioned this pull request Oct 5, 2026

Android: Support predictive back from 3-button navigation flutter/flutter#183642

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justinmc reviewed Nov 2, 2026

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justinmc approved these changes Nov 2, 2026

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muhammadkamel mentioned this pull request Nov 3, 2026

Fix/predictive back event swipe edge out of bounds flutter/flutter#185140

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10 tasks done

		// `_` keeps the switch exhaustive if additional SwipeEdge values
		// are added in the Flutter SDK.

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muhammadkamel commented Aug 18, 2026

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