Improve FocusBehavior: support list view lazy render. support control x:load

[lyf6lyf]

Fixes

PR Type

What kind of change does this PR introduce?

Bugfix
Feature

What is the current behavior?

The App will crash (throws an NullPointerException) if we put a control whose x:Load = False into FocusBehavior list.
The App won't focus on a ListView items when they are deferred rendering.

What is the new behavior?

The App won't crash in above case.
The deferred item will get focus when it is loaded.
The ListView will get focus when its item is rendered.

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Pull Request has been submitted to the documentation repository instructions. Link:
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• New major technical changes in the toolkit have or will be added to the Wiki e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

Other information

[ghost]

Thanks lyf6lyf for opening a Pull Request! The reviewers will test the PR and highlight if there is any conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌

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All CLA requirements met.

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[Rosuavio]

Just a small comment, but otherwise it looks good.

[Rosuavio]

It seems like a flag should be fine instead of counter.

[lyf6lyf]

Thanks, I've push the fix in the new commit.

[ghost]

This PR has been marked as "needs attention 👋" and awaiting a response from the team.

[ghost]

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[XAML-Knight]

Bug fix confirmed.

Unfortunately, though, I was unable to get the (populated) ListView to receive focus, with these changes.

[lyf6lyf]

Bug fix confirmed.

Unfortunately, though, I was unable to get the (populated) ListView to receive focus, with these changes.

@XAML-Knight It works fine on my side. could you try to increase the timeout?

[XAML-Knight]

Hi @lyf6lyf , I tried increasing the timeout, but still couldn't get the ListView (or any item in the ListView) to capture focus.