要实现Android Camera2帧的水平翻转，您可以使用以下代码示例：

首先，在您的Camera2项目中创建一个名为"CameraUtils"的Java类，并在该类中添加以下代码：

import android.graphics.Matrix;
import android.util.Size;
import android.view.Surface;

public class CameraUtils {

    public static void configureTransform(int viewWidth, int viewHeight, Size previewSize, int displayRotation, Matrix matrix) {
        if (null == matrix) {
            return;
        }

        int previewWidth = previewSize.getWidth();
        int previewHeight = previewSize.getHeight();

        int centerX = viewWidth / 2;
        int centerY = viewHeight / 2;

        // Determine the rotation and flip transformations needed
        int rotationDegrees = 0;
        switch (displayRotation) {
            case Surface.ROTATION_0:
                rotationDegrees = 0;
                break;
            case Surface.ROTATION_90:
                rotationDegrees = 90;
                break;
            case Surface.ROTATION_180:
                rotationDegrees = 180;
                break;
            case Surface.ROTATION_270:
                rotationDegrees = 270;
                break;
        }

        matrix.postRotate(-rotationDegrees, centerX, centerY);

        // Apply horizontal flip
        matrix.postScale(-1, 1, centerX, centerY);

        // Resize the texture view to fit the aspect ratio of the preview size
        float scale = Math.max((float) viewHeight / previewHeight, (float) viewWidth / previewWidth);
        float scaledWidth = scale * previewWidth;
        float scaledHeight = scale * previewHeight;
        float deltaX = (viewWidth - scaledWidth) / 2;
        float deltaY = (viewHeight - scaledHeight) / 2;
        matrix.postScale(scale, scale);
        matrix.postTranslate(deltaX, deltaY);
    }
}

然后，在您的Camera2活动或片段类中，您可以在设置TextureView或SurfaceView的预览时调用configureTransform()方法来应用水平翻转，如下所示：

private void setUpCameraOutputs(int width, int height) {
    // ...
    // 在此处设置摄像头输出

    // 配置TextureView或SurfaceView的预览
    int displayRotation = getWindowManager().getDefaultDisplay().getRotation();
    Matrix matrix = new Matrix();
    CameraUtils.configureTransform(textureView.getWidth(), textureView.getHeight(), previewSize, displayRotation, matrix);
    textureView.setTransform(matrix);
}

这些代码将根据设备的旋转和预览尺寸来应用矩阵变换，实现Android Camera2帧的水平翻转。