메모용 = Android Studio (OpenCV)

package com.gigi.disproject;

// 객체추적 (Opencv)

import static android.Manifest.permission.CAMERA;

import android.annotation.TargetApi;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.pm.ActivityInfo;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceView;
import android.view.WindowManager;

import androidx.appcompat.app.AppCompatActivity;

import org.opencv.android.BaseLoaderCallback;
import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.LoaderCallbackInterface;
import org.opencv.android.OpenCVLoader;
import org.opencv.core.Mat;

import java.util.Collections;
import java.util.List;

public class ObjectDetectionActivity extends AppCompatActivity
        implements CameraBridgeViewBase.CvCameraViewListener2 {

    private static final String TAG = "opencv";
    private Mat matInput;
    private Mat matResult;

    private CameraBridgeViewBase mOpenCvCameraView;

    public native void ConvertRGBtoGray(long matAddrInput, long matAddrResult);

    static {
        System.loadLibrary("opencv_java4");
        System.loadLibrary("native-lib");
    }

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

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON,
                WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

        setContentView(R.layout.activity_object_detection);

        mOpenCvCameraView = (CameraBridgeViewBase) findViewById(R.id.o_sv);
        mOpenCvCameraView.setVisibility(SurfaceView.VISIBLE);
        mOpenCvCameraView.setCvCameraViewListener(this);
        mOpenCvCameraView.setCameraIndex(0); // front 1, back 0
    }


    @Override
    public void onPause() {
        super.onPause();
        if(mOpenCvCameraView != null){
            mOpenCvCameraView.disableView();
        }
    }

    @Override
    public void onResume() {
        super.onResume();

        if(!OpenCVLoader.initDebug()){
            Log.d(TAG, "onResume :: Internal OpenCV library not found.");
            OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION, this, mLoaderCallback);
        }else{
            Log.d(TAG, "onResum :: OpenCV library found inside package. Using it!");
            mLoaderCallback.onManagerConnected(LoaderCallbackInterface.SUCCESS);
        }
    }

    public void onDestroy() {
        super.onDestroy();

        if (mOpenCvCameraView != null)
            mOpenCvCameraView.disableView();
    }


    /**
     * This method is invoked when camera preview has started. After this method is invoked
     * the frames will start to be delivered to client via the onCameraFrame() callback.
     *
     * @param width  -  the width of the frames that will be delivered
     * @param height - the height of the frames that will be delivered
     */
    @Override
    public void onCameraViewStarted(int width, int height) {

    }

    /**
     * This method is invoked when camera preview has been stopped for some reason.
     * No frames will be delivered via onCameraFrame() callback after this method is called.
     */
    @Override
    public void onCameraViewStopped() {

    }

    /**
     * This method is invoked when delivery of the frame needs to be done.
     * The returned values - is a modified frame which needs to be displayed on the screen.
     * TODO: pass the parameters specifying the format of the frame (BPP, YUV or RGB and etc)
     *
     * @param inputFrame
     */
    @Override
    public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
        matInput = inputFrame.rgba();

        if(matResult == null){
            matResult = new Mat(matInput.rows(), matInput.cols(), matInput.type());
        }
        ConvertRGBtoGray(matInput.getNativeObjAddr(), matResult.getNativeObjAddr());

        return matResult;
    }

    protected List<? extends CameraBridgeViewBase> getCameraViewList(){
        return Collections.singletonList(mOpenCvCameraView);
    }

    // 퍼미션 관련 메소드
    private static final int CAMERA_PERMISSION_REQUEST_CODE = 200;

    protected void onCameraPermissionGranted() {
        List<? extends CameraBridgeViewBase> cameraViews = getCameraViewList();
        if (cameraViews == null) {
            return;
        }
        for (CameraBridgeViewBase cameraBridgeViewBase: cameraViews) {
            if (cameraBridgeViewBase != null) {
                cameraBridgeViewBase.setCameraPermissionGranted();
            }
        }
    }


    @Override
    protected void onStart() {
        super.onStart();
        boolean havePermission = true;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (checkSelfPermission(CAMERA) != PackageManager.PERMISSION_GRANTED) {
                requestPermissions(new String[]{CAMERA}, CAMERA_PERMISSION_REQUEST_CODE);
            }
        }
        if (havePermission) {
            onCameraPermissionGranted();
        }
    }

    @Override
    @TargetApi(Build.VERSION_CODES.M)
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        if (requestCode == CAMERA_PERMISSION_REQUEST_CODE && grantResults.length > 0
                && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            onCameraPermissionGranted();
        }else{
            showDialogForPermission("앱을 실행하려면 퍼미션을 허가하셔야합니다.");
        }
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }

    @TargetApi(Build.VERSION_CODES.M)
    private void showDialogForPermission(String msg) {
        AlertDialog.Builder builder = new AlertDialog.Builder( ObjectDetectionActivity.this);
        builder.setTitle("알림");
        builder.setMessage(msg);
        builder.setCancelable(false);
        builder.setPositiveButton("예", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id){
                requestPermissions(new String[]{CAMERA}, CAMERA_PERMISSION_REQUEST_CODE);
                Log.d(TAG,"동작확인");
            }
        });
        builder.setNegativeButton("아니오", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface arg0, int arg1) {
                finish();
            }
        });
        builder.create().show();
    }
}