[video_player] Remove added listener before unmounting widget in example

[gadishimwe]

Fixes #122690 by removing added listener before unmounting the widget in the example code. I slightly changed the solution I proposed in the issue. I moved the code to remove the listener from dispose method to the listener itself because the first fix wasn't working in this example. The listener was being called one more time after calling Navigator.pop(context) but before the videoPlayerController.removeListener(listener); is called in dispose method.

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[stuartmorgan-g]

It would also be good to add a test of this issue; we don't currently have tests for the example, but this issue illustrates that it would benefit from tests.

[gadishimwe]

Thanks for the contribution! This will need a version update per our contributing docs (the currently unchecked items in the PR template checklist).

Please give this a clearer name (e.g., _onVideoControllerValueUpdated).

Hey @stuartmorgan, I just pushed a commit that applies the feedback. Thanks

[gadishimwe]

It would also be good to add a test of this issue; we don't currently have tests for the example, but this issue illustrates that it would benefit from tests.

That's true, but I don't know how I can test that. And I'm afraid I don't have enough time to look into it now. If anyone else can add a commit for it, that would be great.

[stuartmorgan-g]

That's true, but I don't know how I can test that.

If the issue is that a certain set of steps in the UI crashes, then it would be tested with an integration test (or a widget test if it reproduces there) that does those steps.

[stuartmorgan-g]

Marking as a draft pending the integration test discussed above.

Anyone interested is welcome to contribute a test.

[stuartmorgan-g]

Since this is marked as a draft and hasn't been updated in several months I'm going to close it to clean out our review queue. Please don't hesitate to submit a new PR if you decide to revisit this. Thanks!