[camera_android_camerax] Add support for NV21 image format

[camsim99]

...wip :) might not even compile yet tbh

Fixes flutter/flutter#145961.

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under¹.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

Note: The Flutter team is currently trialing the use of Gemini Code Assist for GitHub. Comments from the gemini-code-assist bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.

Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩² ↩³

[gemini-code-assist]

Code Review

This pull request introduces support for the NV21 image format in the Android CameraX implementation. This is achieved by adding a new Java utility class to perform the YUV_420_888 to NV21 conversion, and exposing it to Dart via Pigeon. The changes in the Dart layer correctly use this new utility when the camera is initialized for NV21 image streaming.

My review focuses on several critical issues that will prevent the code from compiling, such as incorrect package names, missing imports, and typos in the new Java files. I've also pointed out an incorrect configuration in the Pigeon file. Addressing these points will be necessary to get the PR into a mergeable state.

[gemini-code-assist]

The package declaration io.flutter.plugins.camera.media does not match the file's directory structure. To ensure the class is correctly resolved and to maintain consistency, it should be io.flutter.plugins.camerax.

Suggested change

	package io.flutter.plugins.camera.media;
	package io.flutter.plugins.camerax;

[gemini-code-assist]

This file is missing imports for List and PlaneProxy, which will cause compilation errors.

Suggested change

	import android.media.Image;
	import androidx.annotation.NonNull;
	import java.nio.ByteBuffer;
	import android.media.Image;
	import androidx.annotation.NonNull;
	import androidx.camera.core.ImageProxy.PlaneProxy;
	import java.nio.ByteBuffer;
	import java.util.List;

[gemini-code-assist]

This file is missing imports for java.util.List and java.nio.ByteBuffer, which will cause compilation errors.

import androidx.camera.core.ImageProxy.PlaneProxy;
import androidx.annotation.NonNull;
import java.nio.ByteBuffer;
import java.util.List;

[gemini-code-assist]

The return type bytes[] is not a valid Java type. This should be byte[] to match the expected type for image data buffers.

  public byte[] getNv21Plane(@NonNull List<PlaneProxy> planeProxyList, long imageWidth, long imageHeight) {

[gemini-code-assist]

The fullClassName androidx.camera.core.PlaneProxyUtils appears to be incorrect, as this class does not exist in the AndroidX library. This should point to the new native utility class you've added, which is io.flutter.plugins.camerax.PlaneProxyUtils.

    fullClassName: 'io.flutter.plugins.camerax.PlaneProxyUtils',