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[iOS & Mac] Fix NullReferenceException in CollectionViewHandler2 after handler restore when property changes - #36073
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…r handler restore when ItemsLayout property changes
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June 25, 2026 04:55
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…r handler restore when property changes (#36073) <!-- Please keep the note below for people who find this PR --> > [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment whether this change resolves your issue. Thank you! <!-- !!!!!!! MAIN IS THE ONLY ACTIVE BRANCH. MAKE SURE THIS PR IS TARGETING MAIN. !!!!!!! --> This pull request addresses a regression issue where `CollectionViewHandler2` could throw a `NullReferenceException` if a layout property changed after the handler was disconnected and then reconnected. The fix ensures the internal cache is properly reinitialized, and new tests are added to verify the handler's stability in these scenarios. ### Description of Change **Bug fix:** - Ensured `_layoutPropertyCache` is reinitialized when subscribing to a new items layout in `CollectionViewHandler2`, preventing `NullReferenceException` after handler disconnect/reconnect cycles. **Testing improvements:** - Added regression tests to confirm that changing properties on `GridItemsLayout` and `LinearItemsLayout` after a disconnect/restore cycle does not cause crashes in `CollectionViewHandler2`. These tests cover various property changes and validate the fix <!-- Enter description of the fix in this section --> ### Issues Fixed <!-- Please make sure that there is a bug logged for the issue being fixed. The bug should describe the problem and how to reproduce it. --> Fixes #36010 ### Tested the behavior in the following platforms - [ ] Windows - [ ] Android - [x] iOS - [x] Mac | Before Issue Fix | After Issue Fix | |----------|----------| | <img width="954" height="693" alt="BeforeFix36010" src="https://github.com/user-attachments/assets/fb32509b-ce7c-497c-9fa4-3170181e9475" /> | <img width="947" height="689" alt="AfterFix36010" src="https://github.com/user-attachments/assets/188f6e3b-6b72-4ead-9af0-342d5d8d7c20" /> | <!-- Are you targeting main? All PRs should target the main branch unless otherwise noted. -->
kubaflo
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Jul 3, 2026
…r handler restore when property changes (#36073) <!-- Please keep the note below for people who find this PR --> > [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment whether this change resolves your issue. Thank you! <!-- !!!!!!! MAIN IS THE ONLY ACTIVE BRANCH. MAKE SURE THIS PR IS TARGETING MAIN. !!!!!!! --> This pull request addresses a regression issue where `CollectionViewHandler2` could throw a `NullReferenceException` if a layout property changed after the handler was disconnected and then reconnected. The fix ensures the internal cache is properly reinitialized, and new tests are added to verify the handler's stability in these scenarios. ### Description of Change **Bug fix:** - Ensured `_layoutPropertyCache` is reinitialized when subscribing to a new items layout in `CollectionViewHandler2`, preventing `NullReferenceException` after handler disconnect/reconnect cycles. **Testing improvements:** - Added regression tests to confirm that changing properties on `GridItemsLayout` and `LinearItemsLayout` after a disconnect/restore cycle does not cause crashes in `CollectionViewHandler2`. These tests cover various property changes and validate the fix <!-- Enter description of the fix in this section --> ### Issues Fixed <!-- Please make sure that there is a bug logged for the issue being fixed. The bug should describe the problem and how to reproduce it. --> Fixes #36010 ### Tested the behavior in the following platforms - [ ] Windows - [ ] Android - [x] iOS - [x] Mac | Before Issue Fix | After Issue Fix | |----------|----------| | <img width="954" height="693" alt="BeforeFix36010" src="https://github.com/user-attachments/assets/fb32509b-ce7c-497c-9fa4-3170181e9475" /> | <img width="947" height="689" alt="AfterFix36010" src="https://github.com/user-attachments/assets/188f6e3b-6b72-4ead-9af0-342d5d8d7c20" /> | <!-- Are you targeting main? All PRs should target the main branch unless otherwise noted. -->
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Jul 6, 2026
…r handler restore when property changes (#36073) <!-- Please keep the note below for people who find this PR --> > [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment whether this change resolves your issue. Thank you! <!-- !!!!!!! MAIN IS THE ONLY ACTIVE BRANCH. MAKE SURE THIS PR IS TARGETING MAIN. !!!!!!! --> This pull request addresses a regression issue where `CollectionViewHandler2` could throw a `NullReferenceException` if a layout property changed after the handler was disconnected and then reconnected. The fix ensures the internal cache is properly reinitialized, and new tests are added to verify the handler's stability in these scenarios. ### Description of Change **Bug fix:** - Ensured `_layoutPropertyCache` is reinitialized when subscribing to a new items layout in `CollectionViewHandler2`, preventing `NullReferenceException` after handler disconnect/reconnect cycles. **Testing improvements:** - Added regression tests to confirm that changing properties on `GridItemsLayout` and `LinearItemsLayout` after a disconnect/restore cycle does not cause crashes in `CollectionViewHandler2`. These tests cover various property changes and validate the fix <!-- Enter description of the fix in this section --> ### Issues Fixed <!-- Please make sure that there is a bug logged for the issue being fixed. The bug should describe the problem and how to reproduce it. --> Fixes #36010 ### Tested the behavior in the following platforms - [ ] Windows - [ ] Android - [x] iOS - [x] Mac | Before Issue Fix | After Issue Fix | |----------|----------| | <img width="954" height="693" alt="BeforeFix36010" src="https://github.com/user-attachments/assets/fb32509b-ce7c-497c-9fa4-3170181e9475" /> | <img width="947" height="689" alt="AfterFix36010" src="https://github.com/user-attachments/assets/188f6e3b-6b72-4ead-9af0-342d5d8d7c20" /> | <!-- Are you targeting main? All PRs should target the main branch unless otherwise noted. -->
PureWeen
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Jul 7, 2026
…r handler restore when property changes (#36073) <!-- Please keep the note below for people who find this PR --> > [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment whether this change resolves your issue. Thank you! <!-- !!!!!!! MAIN IS THE ONLY ACTIVE BRANCH. MAKE SURE THIS PR IS TARGETING MAIN. !!!!!!! --> This pull request addresses a regression issue where `CollectionViewHandler2` could throw a `NullReferenceException` if a layout property changed after the handler was disconnected and then reconnected. The fix ensures the internal cache is properly reinitialized, and new tests are added to verify the handler's stability in these scenarios. ### Description of Change **Bug fix:** - Ensured `_layoutPropertyCache` is reinitialized when subscribing to a new items layout in `CollectionViewHandler2`, preventing `NullReferenceException` after handler disconnect/reconnect cycles. **Testing improvements:** - Added regression tests to confirm that changing properties on `GridItemsLayout` and `LinearItemsLayout` after a disconnect/restore cycle does not cause crashes in `CollectionViewHandler2`. These tests cover various property changes and validate the fix <!-- Enter description of the fix in this section --> ### Issues Fixed <!-- Please make sure that there is a bug logged for the issue being fixed. The bug should describe the problem and how to reproduce it. --> Fixes #36010 ### Tested the behavior in the following platforms - [ ] Windows - [ ] Android - [x] iOS - [x] Mac | Before Issue Fix | After Issue Fix | |----------|----------| | <img width="954" height="693" alt="BeforeFix36010" src="https://github.com/user-attachments/assets/fb32509b-ce7c-497c-9fa4-3170181e9475" /> | <img width="947" height="689" alt="AfterFix36010" src="https://github.com/user-attachments/assets/188f6e3b-6b72-4ead-9af0-342d5d8d7c20" /> | <!-- Are you targeting main? All PRs should target the main branch unless otherwise noted. -->
PureWeen
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Jul 7, 2026
…r handler restore when property changes (#36073) <!-- Please keep the note below for people who find this PR --> > [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment whether this change resolves your issue. Thank you! <!-- !!!!!!! MAIN IS THE ONLY ACTIVE BRANCH. MAKE SURE THIS PR IS TARGETING MAIN. !!!!!!! --> This pull request addresses a regression issue where `CollectionViewHandler2` could throw a `NullReferenceException` if a layout property changed after the handler was disconnected and then reconnected. The fix ensures the internal cache is properly reinitialized, and new tests are added to verify the handler's stability in these scenarios. ### Description of Change **Bug fix:** - Ensured `_layoutPropertyCache` is reinitialized when subscribing to a new items layout in `CollectionViewHandler2`, preventing `NullReferenceException` after handler disconnect/reconnect cycles. **Testing improvements:** - Added regression tests to confirm that changing properties on `GridItemsLayout` and `LinearItemsLayout` after a disconnect/restore cycle does not cause crashes in `CollectionViewHandler2`. These tests cover various property changes and validate the fix <!-- Enter description of the fix in this section --> ### Issues Fixed <!-- Please make sure that there is a bug logged for the issue being fixed. The bug should describe the problem and how to reproduce it. --> Fixes #36010 ### Tested the behavior in the following platforms - [ ] Windows - [ ] Android - [x] iOS - [x] Mac | Before Issue Fix | After Issue Fix | |----------|----------| | <img width="954" height="693" alt="BeforeFix36010" src="https://github.com/user-attachments/assets/fb32509b-ce7c-497c-9fa4-3170181e9475" /> | <img width="947" height="689" alt="AfterFix36010" src="https://github.com/user-attachments/assets/188f6e3b-6b72-4ead-9af0-342d5d8d7c20" /> | <!-- Are you targeting main? All PRs should target the main branch unless otherwise noted. -->
kubaflo
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Jul 10, 2026
…r handler restore when property changes (#36073) <!-- Please keep the note below for people who find this PR --> > [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment whether this change resolves your issue. Thank you! <!-- !!!!!!! MAIN IS THE ONLY ACTIVE BRANCH. MAKE SURE THIS PR IS TARGETING MAIN. !!!!!!! --> This pull request addresses a regression issue where `CollectionViewHandler2` could throw a `NullReferenceException` if a layout property changed after the handler was disconnected and then reconnected. The fix ensures the internal cache is properly reinitialized, and new tests are added to verify the handler's stability in these scenarios. ### Description of Change **Bug fix:** - Ensured `_layoutPropertyCache` is reinitialized when subscribing to a new items layout in `CollectionViewHandler2`, preventing `NullReferenceException` after handler disconnect/reconnect cycles. **Testing improvements:** - Added regression tests to confirm that changing properties on `GridItemsLayout` and `LinearItemsLayout` after a disconnect/restore cycle does not cause crashes in `CollectionViewHandler2`. These tests cover various property changes and validate the fix <!-- Enter description of the fix in this section --> ### Issues Fixed <!-- Please make sure that there is a bug logged for the issue being fixed. The bug should describe the problem and how to reproduce it. --> Fixes #36010 ### Tested the behavior in the following platforms - [ ] Windows - [ ] Android - [x] iOS - [x] Mac | Before Issue Fix | After Issue Fix | |----------|----------| | <img width="954" height="693" alt="BeforeFix36010" src="https://github.com/user-attachments/assets/fb32509b-ce7c-497c-9fa4-3170181e9475" /> | <img width="947" height="689" alt="AfterFix36010" src="https://github.com/user-attachments/assets/188f6e3b-6b72-4ead-9af0-342d5d8d7c20" /> | <!-- Are you targeting main? All PRs should target the main branch unless otherwise noted. -->
kubaflo
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Jul 15, 2026
…r handler restore when property changes (#36073) <!-- Please keep the note below for people who find this PR --> > [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment whether this change resolves your issue. Thank you! <!-- !!!!!!! MAIN IS THE ONLY ACTIVE BRANCH. MAKE SURE THIS PR IS TARGETING MAIN. !!!!!!! --> This pull request addresses a regression issue where `CollectionViewHandler2` could throw a `NullReferenceException` if a layout property changed after the handler was disconnected and then reconnected. The fix ensures the internal cache is properly reinitialized, and new tests are added to verify the handler's stability in these scenarios. ### Description of Change **Bug fix:** - Ensured `_layoutPropertyCache` is reinitialized when subscribing to a new items layout in `CollectionViewHandler2`, preventing `NullReferenceException` after handler disconnect/reconnect cycles. **Testing improvements:** - Added regression tests to confirm that changing properties on `GridItemsLayout` and `LinearItemsLayout` after a disconnect/restore cycle does not cause crashes in `CollectionViewHandler2`. These tests cover various property changes and validate the fix <!-- Enter description of the fix in this section --> ### Issues Fixed <!-- Please make sure that there is a bug logged for the issue being fixed. The bug should describe the problem and how to reproduce it. --> Fixes #36010 ### Tested the behavior in the following platforms - [ ] Windows - [ ] Android - [x] iOS - [x] Mac | Before Issue Fix | After Issue Fix | |----------|----------| | <img width="954" height="693" alt="BeforeFix36010" src="https://github.com/user-attachments/assets/fb32509b-ce7c-497c-9fa4-3170181e9475" /> | <img width="947" height="689" alt="AfterFix36010" src="https://github.com/user-attachments/assets/188f6e3b-6b72-4ead-9af0-342d5d8d7c20" /> | <!-- Are you targeting main? All PRs should target the main branch unless otherwise noted. -->
kubaflo
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Jul 22, 2026
…r handler restore when property changes (#36073) <!-- Please keep the note below for people who find this PR --> > [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment whether this change resolves your issue. Thank you! <!-- !!!!!!! MAIN IS THE ONLY ACTIVE BRANCH. MAKE SURE THIS PR IS TARGETING MAIN. !!!!!!! --> This pull request addresses a regression issue where `CollectionViewHandler2` could throw a `NullReferenceException` if a layout property changed after the handler was disconnected and then reconnected. The fix ensures the internal cache is properly reinitialized, and new tests are added to verify the handler's stability in these scenarios. ### Description of Change **Bug fix:** - Ensured `_layoutPropertyCache` is reinitialized when subscribing to a new items layout in `CollectionViewHandler2`, preventing `NullReferenceException` after handler disconnect/reconnect cycles. **Testing improvements:** - Added regression tests to confirm that changing properties on `GridItemsLayout` and `LinearItemsLayout` after a disconnect/restore cycle does not cause crashes in `CollectionViewHandler2`. These tests cover various property changes and validate the fix <!-- Enter description of the fix in this section --> ### Issues Fixed <!-- Please make sure that there is a bug logged for the issue being fixed. The bug should describe the problem and how to reproduce it. --> Fixes #36010 ### Tested the behavior in the following platforms - [ ] Windows - [ ] Android - [x] iOS - [x] Mac | Before Issue Fix | After Issue Fix | |----------|----------| | <img width="954" height="693" alt="BeforeFix36010" src="https://github.com/user-attachments/assets/fb32509b-ce7c-497c-9fa4-3170181e9475" /> | <img width="947" height="689" alt="AfterFix36010" src="https://github.com/user-attachments/assets/188f6e3b-6b72-4ead-9af0-342d5d8d7c20" /> | <!-- Are you targeting main? All PRs should target the main branch unless otherwise noted. -->
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It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment whether this change resolves your issue. Thank you!
This pull request addresses a regression issue where
CollectionViewHandler2could throw aNullReferenceExceptionif a layout property changed after the handler was disconnected and then reconnected. The fix ensures the internal cache is properly reinitialized, and new tests are added to verify the handler's stability in these scenarios.Description of Change
Bug fix:
_layoutPropertyCacheis reinitialized when subscribing to a new items layout inCollectionViewHandler2, preventingNullReferenceExceptionafter handler disconnect/reconnect cycles.Testing improvements:
GridItemsLayoutandLinearItemsLayoutafter a disconnect/restore cycle does not cause crashes inCollectionViewHandler2. These tests cover various property changes and validate the fixIssues Fixed
Fixes #36010
Tested the behavior in the following platforms