Clarify why the child is nullable in AnimatedTransitionBuilder#182995
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This pull request clarifies why the child parameter is nullable in AnimatedTransitionBuilder and DualTransitionBuilder by adding documentation. My review points out a slight inaccuracy in the new documentation for DualTransitionBuilder.child and suggests a more precise wording to improve correctness.
| /// This child widget will be wrapped by the transitions built by | ||
| /// [forwardBuilder] and [reverseBuilder]. | ||
| /// | ||
| /// The [child] is passed to the [reverseBuilder], and the result of that is |
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The first sentence here seems to restate the sentence before it. I think we can remove it.
| /// [forwardBuilder] and [reverseBuilder]. | ||
| /// | ||
| /// The [child] is passed to the [reverseBuilder], and the result of that is | ||
| /// in turn passed to the [forwardBuilder]. This allows for efficient |
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Suggest using docs from https://api.flutter.dev/flutter/widgets/TweenAnimationBuilder/child.html as inspiration:
If a builder callback's return value contains a subtree that does not depend on the animation, it's more efficient to build that subtree once instead of rebuilding it on every animation tick.
If the pre-built subtree is passed as the child parameter, the AnimatedTransitionBuilder will pass it back to the builder function so that it can be incorporated into the build.
Using this pre-built child is entirely optional, but can improve performance significantly in some cases and is therefore a good practice.
Renzo-Olivares
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Mar 31, 2026
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LGTM, thank you for the contribution @AbdeMohlbi. This will need a secondary review before merging it.
justinmc
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Apr 7, 2026
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Looks good but I think you forgot a part of the sentence that I commented on, if I'm understanding correctly.
| /// | ||
| /// The `animation` provided to the builder always runs forward from 0.0 to 1.0. | ||
| /// | ||
| /// An optional, pre-built widget subtree that does not depend on the animation's value. |
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Is this the description of the child parameter but your forgot to include that?
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well it was intentional but i did update it once more, to make everyone happy, hope this is what u meant.
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flutter/flutter@31f1802...8e8a194 2026-04-17 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Fix ImageInfo.isCloneOf to correctly compare scale values (fixes #184626) (#184643)" (flutter/flutter#185203) 2026-04-17 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Roll Fuchsia Test Scripts from R2EllDf4DgBXVNuiN... to dQ4PjIJB5kZFU8Y32... (#185192)" (flutter/flutter#185199) 2026-04-17 chris@bracken.jp [iOS] Migrate FlutterLaunchEngine to Swift (flutter/flutter#185151) 2026-04-17 116356835+AbdeMohlbi@users.noreply.github.com Remove unused `FlutterRunArguments.java` file (flutter/flutter#184160) 2026-04-17 engine-flutter-autoroll@skia.org Roll Fuchsia Test Scripts from R2EllDf4DgBXVNuiN... to dQ4PjIJB5kZFU8Y32... (flutter/flutter#185192) 2026-04-17 pewpewstol@gmail.com [Impeller] Fix morphology filter asymmetric dilation/erosion (flutter/flutter#184913) 2026-04-17 nate.w5687@gmail.com `AnimationStyle` methods (flutter/flutter#182333) 2026-04-17 karan@solvejet.net Fix _scheduleSystemFontsUpdate assertion during non-idle scheduler phase (flutter/flutter#184332) 2026-04-17 154381524+flutteractionsbot@users.noreply.github.com Revert "Unpin sdk package dependencies" (flutter/flutter#185186) 2026-04-16 116356835+AbdeMohlbi@users.noreply.github.com Clarify why the `child` is nullable in `AnimatedTransitionBuilder` (flutter/flutter#182995) 2026-04-16 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from IdBT8fSMYrYSip65j... to di3JdYrdE9OFu8Iyl... (flutter/flutter#185173) 2026-04-16 1063596+reidbaker@users.noreply.github.com Add dart_skills_lint to dev/tool with test and update readme instructions for new skills authors (flutter/flutter#185033) 2026-04-16 flar@google.com [Impeller] Provide std::optional getter for stroke property (flutter/flutter#185112) 2026-04-16 katelovett@google.com Validate itemExtent with geometry in RenderSliverFixedExtentBoxAdaptor (flutter/flutter#185159) 2026-04-16 152433210+mozammal-hossain@users.noreply.github.com [iOS] Clarify provisioning profile error instructions (flutter/flutter#184051) 2026-04-16 bkonyi@google.com [Widget Preview] Fix flaky integration test timeout during flutter clean (flutter/flutter#184991) 2026-04-16 engine-flutter-autoroll@skia.org Roll Dart SDK from fbddcbe0cd96 to 7c2564c18770 (2 revisions) (flutter/flutter#185143) 2026-04-16 sigurdm@google.com Unpin sdk package dependencies (flutter/flutter#184821) 2026-04-16 68919043+Istiak-Ahmed78@users.noreply.github.com Fix ImageInfo.isCloneOf to correctly compare scale values (fixes #184626) (flutter/flutter#184643) 2026-04-16 engine-flutter-autoroll@skia.org Roll Skia from 391cdbe3ffe9 to d8415c5d7b91 (2 revisions) (flutter/flutter#185141) 2026-04-16 154381524+flutteractionsbot@users.noreply.github.com Sync CHANGELOG.md from stable (flutter/flutter#185166) 2026-04-16 154381524+flutteractionsbot@users.noreply.github.com Revert "Move widget_preview_scaffold into pub workspace" (flutter/flutter#185164) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC boetger@google.com,stuartmorgan@google.com on the revert to ensure that a human is aware of the problem. To file a bug in Packages: 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: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
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…r#11523) flutter/flutter@31f1802...8e8a194 2026-04-17 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Fix ImageInfo.isCloneOf to correctly compare scale values (fixes #184626) (#184643)" (flutter/flutter#185203) 2026-04-17 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Roll Fuchsia Test Scripts from R2EllDf4DgBXVNuiN... to dQ4PjIJB5kZFU8Y32... (#185192)" (flutter/flutter#185199) 2026-04-17 chris@bracken.jp [iOS] Migrate FlutterLaunchEngine to Swift (flutter/flutter#185151) 2026-04-17 116356835+AbdeMohlbi@users.noreply.github.com Remove unused `FlutterRunArguments.java` file (flutter/flutter#184160) 2026-04-17 engine-flutter-autoroll@skia.org Roll Fuchsia Test Scripts from R2EllDf4DgBXVNuiN... to dQ4PjIJB5kZFU8Y32... (flutter/flutter#185192) 2026-04-17 pewpewstol@gmail.com [Impeller] Fix morphology filter asymmetric dilation/erosion (flutter/flutter#184913) 2026-04-17 nate.w5687@gmail.com `AnimationStyle` methods (flutter/flutter#182333) 2026-04-17 karan@solvejet.net Fix _scheduleSystemFontsUpdate assertion during non-idle scheduler phase (flutter/flutter#184332) 2026-04-17 154381524+flutteractionsbot@users.noreply.github.com Revert "Unpin sdk package dependencies" (flutter/flutter#185186) 2026-04-16 116356835+AbdeMohlbi@users.noreply.github.com Clarify why the `child` is nullable in `AnimatedTransitionBuilder` (flutter/flutter#182995) 2026-04-16 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from IdBT8fSMYrYSip65j... to di3JdYrdE9OFu8Iyl... (flutter/flutter#185173) 2026-04-16 1063596+reidbaker@users.noreply.github.com Add dart_skills_lint to dev/tool with test and update readme instructions for new skills authors (flutter/flutter#185033) 2026-04-16 flar@google.com [Impeller] Provide std::optional getter for stroke property (flutter/flutter#185112) 2026-04-16 katelovett@google.com Validate itemExtent with geometry in RenderSliverFixedExtentBoxAdaptor (flutter/flutter#185159) 2026-04-16 152433210+mozammal-hossain@users.noreply.github.com [iOS] Clarify provisioning profile error instructions (flutter/flutter#184051) 2026-04-16 bkonyi@google.com [Widget Preview] Fix flaky integration test timeout during flutter clean (flutter/flutter#184991) 2026-04-16 engine-flutter-autoroll@skia.org Roll Dart SDK from fbddcbe0cd96 to 7c2564c18770 (2 revisions) (flutter/flutter#185143) 2026-04-16 sigurdm@google.com Unpin sdk package dependencies (flutter/flutter#184821) 2026-04-16 68919043+Istiak-Ahmed78@users.noreply.github.com Fix ImageInfo.isCloneOf to correctly compare scale values (fixes #184626) (flutter/flutter#184643) 2026-04-16 engine-flutter-autoroll@skia.org Roll Skia from 391cdbe3ffe9 to d8415c5d7b91 (2 revisions) (flutter/flutter#185141) 2026-04-16 154381524+flutteractionsbot@users.noreply.github.com Sync CHANGELOG.md from stable (flutter/flutter#185166) 2026-04-16 154381524+flutteractionsbot@users.noreply.github.com Revert "Move widget_preview_scaffold into pub workspace" (flutter/flutter#185164) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC boetger@google.com,stuartmorgan@google.com on the revert to ensure that a human is aware of the problem. To file a bug in Packages: 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: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
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Fixes: #77467
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