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Merged
fluttergithubbot merged 1 commit into from
Jun 8, 2022
Merged

Fix PageView throws Null check error #104405

fluttergithubbot merged 1 commit into from
Jun 8, 2022

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@bleroux
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@bleroux bleroux commented May 23, 2022 •
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Description

This PR fixes a null check error in PageView.

The null check was added by the following PR : #65015

Flutter 3.0 is the first stable release where the null check error surfaces.
It surfaces due to the following PR : #97971
which added a call to MediaQuery in SrollableState.didChangeDependencies (line 462) :

  @override
  void didChangeDependencies() {
    _mediaQueryData = MediaQuery.maybeOf(context);
    _updatePosition();
    super.didChangeDependencies();
  }

During startup, especially in release mode, MediaQuery.of(context).size might return (0,0). The size will be updated when the native platform reports the actual resolution (several milliseconds later). This seems to be by design for performance reasons (see #25827 (comment)).

For PageView, it means that the Viewport dimensions are updated during startup which was not expected with the previous code.

Related Issue

Fixes #101007

Tests

Adds 1 test.

@flutter-dashboard flutter-dashboard bot added the framework flutter/packages/flutter repository. See also f: labels. label May 23, 2022
@bleroux bleroux force-pushed the fix_page_view_null_check_error branch 3 times, most recently from f44c7cf to 531feee Compare May 24, 2022 06:52
@goderbauer goderbauer requested a review from Piinks May 25, 2022 21:39
@bleroux bleroux mentioned this pull request May 28, 2022
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LGTM! Thank you for fixing this! @xu-baolin WDYT?

@xu-baolin
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xu-baolin commented Jun 8, 2022 •
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Hey @Piinks this issue is similar to this #103328,
We should override absorb when the _PagePosition was replaced.

  @override
  void absorb(ScrollPosition other) {
    super.absorb(other);
    assert(_cachedPage == null);

    if (other is! _PagePosition) {
      return;
    }

    if (other._cachedPage != null) {
      _cachedPage = other._cachedPage;
      other._cachedPage = null;
    }
  }

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See the comment above.

@bleroux bleroux force-pushed the fix_page_view_null_check_error branch from 531feee to d335c33 Compare June 8, 2022 08:47
@bleroux bleroux force-pushed the fix_page_view_null_check_error branch from d335c33 to b15311e Compare June 8, 2022 08:49
@bleroux bleroux requested a review from xu-baolin June 8, 2022 09:25
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LGTM，need a second review from @Piinks

@bleroux bleroux requested a review from Piinks June 8, 2022 12:17
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Ah nice @xu-baolin! Thanks @bleroux, LGTM!

@Piinks Piinks added waiting for tree to go green f: scrolling Viewports, list views, slivers, etc. labels Jun 8, 2022
@fluttergithubbot fluttergithubbot merged commit 4dec56b into flutter:master Jun 8, 2022
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4dec56b Fix PageView throws Null check error (flutter/flutter#104405)
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4dec56b Fix PageView throws Null check error (flutter/flutter#104405)
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4dec56b Fix PageView throws Null check error (flutter/flutter#104405)
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4dec56b Fix PageView throws Null check error (flutter/flutter#104405)
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4dec56b Fix PageView throws Null check error (flutter/flutter#104405)
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4dec56b Fix PageView throws Null check error (flutter/flutter#104405)
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4dec56b Fix PageView throws Null check error (flutter/flutter#104405)
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4dec56b Fix PageView throws Null check error (flutter/flutter#104405)
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@bleroux bleroux deleted the fix_page_view_null_check_error branch June 17, 2022 09:47
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@armandojimenez
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armandojimenez commented Jul 11, 2022 •
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Anyone knows when is this landing on stable branch?

idealclover added a commit to idealclover/Caritas-APP that referenced this pull request Jul 13, 2022
@idealclover
☠️ trick way to fix a bug
4f28299 
wait for flutter/flutter#104405
@ffamar
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ffamar commented Jul 15, 2022

The issue still exist in the flutter version 3.0.5.
Anyone knows when the patch will be released?

@alexaung
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alexaung commented Jul 20, 2022

Yes still happening in version 3.0.5

@bleroux
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bleroux commented Jul 20, 2022

From https://github.com/flutter/flutter/wiki/Flutter-build-release-channels,
"Roughly once a quarter, a branch that has been stabilized on beta will become our next stable branch and we will create a stable release from that branch".

@antonshkurenko
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antonshkurenko commented Jul 21, 2022

Is this expected to be fixed in 3.0.5 and it's an issue again or it wasn't included in 3.0.5?

@bleroux
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bleroux commented Jul 21, 2022

@tonyshkurenko
It was not included in 3.0.5.
For the moment, this fix is available in the master channel and in the 3.3 beta channel.

camsim99 pushed a commit to camsim99/flutter that referenced this pull request Aug 10, 2022
@bleroux @camsim99
Fix PageView throws Null check error (flutter#104405)
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engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 30, 2022
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4dec56b Fix PageView throws Null check error (flutter/flutter#104405)
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engine-flutter-autoroll added a commit to engine-flutter-autoroll/plugins that referenced this pull request Aug 30, 2022
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4dec56b Fix PageView throws Null check error (flutter/flutter#104405)
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ffamar commented Aug 31, 2022

I confirm, issue fixed in 3.3.0 release.

@victor-tinoco victor-tinoco mentioned this pull request Aug 10, 2023
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@Piinks Piinks mentioned this pull request Aug 6, 2024
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PageView applyViewportDimension throws Null check operator used on a null value

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@bleroux @xu-baolin @armandojimenez @ffamar @alexaung @antonshkurenko @Piinks @fluttergithubbot