[android] Fix black and blank screen issues on the platform view page.

[0xZOne]

Fix issues:
#88558
#88845

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• I added new tests to check the change I am making.
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• All existing and new tests are passing.

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[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

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[eggfly]

Maybe a solution is not setting flutterImageView and previousRenderSurface to null in detachFromFlutterEngine()?

public void detachFromFlutterEngine() {
    Log.v(TAG, "Detaching from a FlutterEngine: " + flutterEngine);

    // ... 

    // flutterImageView = null;
    // previousRenderSurface = null;
    flutterEngine = null;
}

@0xZOne

[0xZOne]

Maybe a solution is not setting flutterImageView and previousRenderSurface to null in detachFromFlutterEngine()?

public void detachFromFlutterEngine() {
    Log.v(TAG, "Detaching from a FlutterEngine: " + flutterEngine);

    // ... 

    // flutterImageView = null;
    // previousRenderSurface = null;
    flutterEngine = null;
}

@0xZOne

We need to revert |renderSurface| to |previousRenderSurface| here to avoid a black screen due to the surface missing when it attaches to the engine again. #88845

[blasten]

This is a good fix. However, can we add a test to FlutterViewTest?

One possible test is:

1. Make renderSurface visible for testing. (Remove private modifier).
2. Construct FlutterView
3. Call convertToImageView()
4. Verify renderSurface is a FlutterImageView
5. Call detachFromFlutterEngine()
6. Verify renderSurface is not a FlutterImageView

[0xZOne]

This is a good fix. However, can we add a test to FlutterViewTest?

One possible test is:

1. Make renderSurface visible for testing. (Remove private modifier).
2. Construct FlutterView
3. Call convertToImageView()
4. Verify renderSurface is a FlutterImageView
5. Call detachFromFlutterEngine()
6. Verify renderSurface is not a FlutterImageView

done.

[0xZOne]

Those tests seem interrupted by user for some reason. Can anyone help rebuild, please? thanks.

[ColdPaleLight]

Those tests seem interrupted by user for some reason. Can anyone help rebuild, please? thanks.

Done

[0xZOne]

Linux Framework Smoke Tests failure is unrelated to my changes. See #28535 for details.

[chinmaygarde]

This patch needs to be rebased on ToT for the presubmits to run again please? And CC @blasten for the re-review.

[blasten]

LGTM - nicely done