要实现Android OpenCV识别建筑物的部分，可以按照以下步骤进行：

1. 确保Android项目已正确设置OpenCV库。可以参考OpenCV官方文档或其他教程进行配置。
2. 在Android项目中创建一个新的Java类，例如BuildingDetector.java。
3. 在BuildingDetector.java中导入OpenCV库和其他必要的类：

import org.opencv.android.Utils;
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.MatOfRect;
import org.opencv.core.Rect;
import org.opencv.core.Scalar;
import org.opencv.core.Size;
import org.opencv.core.CvType;
import org.opencv.objdetect.CascadeClassifier;
import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewFrame;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewListener2;
import org.opencv.android.OpenCVLoader;
import org.opencv.android.BaseLoaderCallback;
import org.opencv.android.LoaderCallbackInterface;
import org.opencv.android.CameraBridgeViewBase;

4. 添加必要的变量：

private CascadeClassifier cascadeClassifier;
private Mat grayscaleImage;
private int absoluteFaceSize;
private CameraBridgeViewBase mOpenCvCameraView;

5. 实现BaseLoaderCallback以确保OpenCV成功加载：

private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
    @Override
    public void onManagerConnected(int status) {
        switch (status) {
            case LoaderCallbackInterface.SUCCESS: {
                initializeOpenCVDependencies();
                break;
            }
            default: {
                super.onManagerConnected(status);
                break;
            }
        }
    }
};

6. 在onResume()方法中加载OpenCV：

@Override
protected void onResume() {
    super.onResume();
    OpenCVLoader.initDebug();
    if (!OpenCVLoader.initDebug()) {
        OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION, this, mLoaderCallback);
    } else {
        mLoaderCallback.onManagerConnected(LoaderCallbackInterface.SUCCESS);
    }
}

7. 在initializeOpenCVDependencies()方法中加载分类器和相机视图：

private void initializeOpenCVDependencies() {
    try {
        // 加载分类器
        InputStream is = getResources().openRawResource(R.raw.cascade_classifier);
        File cascadeDir = getDir("cascade", Context.MODE_PRIVATE);
        File cascadeFile = new File(cascadeDir, "cascade.xml");
        FileOutputStream fos = new FileOutputStream(cascadeFile);

        byte[] buffer = new byte[4096];
        int bytesRead;
        while ((bytesRead = is.read(buffer)) != -1) {
            fos.write(buffer, 0, bytesRead);
        }
        is.close();
        fos.close();

        cascadeClassifier = new CascadeClassifier(cascadeFile.getAbsolutePath());
        cascadeClassifier.load(cascadeFile.getAbsolutePath());

        // 初始化相机视图
        mOpenCvCameraView.enableView();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

8. 实现CvCameraViewListener2以处理每一帧的图像：

private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
    @Override
    public void onManagerConnected(int status) {
        switch (status) {
            case LoaderCallbackInterface.SUCCESS: {
                initializeOpenCVDependencies();
                break;
            }
            default: {
                super.onManagerConnected(status);
                break;
            }
        }
    }
};

private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
    @Override
    public void onManagerConnected(int status) {
        switch (status) {
            case LoaderCallbackInterface.SUCCESS: {
                initializeOpenCVDependencies();
                break;
            }
            default: {
                super.onManagerConnected(status);
                break;
            }
        }
    }
};

private CvCameraViewListener2 mCameraViewListener = new CvCameraViewListener2() {
    @Override
    public void onCameraViewStarted(int width, int height) {
        grayscaleImage = new Mat(height, width, CvType.CV_8UC4);
        absoluteFaceSize = (int) (height * 0.2);
    }

    @Override
    public void onCameraViewStopped() {
        grayscaleImage.release();
    }

    @Override
    public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
        Mat frame = inputFrame.rgba();
        Imgproc.cvtColor(frame, grayscaleImage, Imgproc.COLOR_RGBA2GRAY);

        MatOfRect buildings = new MatOfRect();