MainActivity.java

package com.example.nativeopencvandroidtemplate;

import android.Manifest;
import android.app.Activity;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.util.Log;
import android.view.SurfaceView;
import android.view.WindowManager;
import android.widget.Toast;

import org.jetbrains.annotations.NotNull;
import org.opencv.android.BaseLoaderCallback;
import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewFrame;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewListener2;
import org.opencv.android.LoaderCallbackInterface;
import org.opencv.android.OpenCVLoader;
import org.opencv.core.Mat;

public class MainActivity extends Activity implements CvCameraViewListener2 {
    private static final String TAG = "MainActivity";
    private static final int CAMERA_PERMISSION_REQUEST = 1;

    private CameraBridgeViewBase mOpenCvCameraView;

    private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
        @Override
        public void onManagerConnected(int status) {
            if (status == LoaderCallbackInterface.SUCCESS) {
                Log.i(TAG, "OpenCV loaded successfully");

                // Load native library after(!) OpenCV initialization
                System.loadLibrary("native-lib");

                mOpenCvCameraView.enableView();
            } else {
                super.onManagerConnected(status);
            }
        }
    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        Log.i(TAG, "called onCreate");
        super.onCreate(savedInstanceState);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

        // Permissions for Android 6+
        ActivityCompat.requestPermissions(
                this,
                new String[]{Manifest.permission.CAMERA},
                CAMERA_PERMISSION_REQUEST
        );

        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        setContentView(R.layout.activity_main);

        mOpenCvCameraView = findViewById(R.id.main_surface);

        mOpenCvCameraView.setVisibility(SurfaceView.VISIBLE);

        mOpenCvCameraView.setCvCameraViewListener(this);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NotNull String[] permissions, @NotNull int[] grantResults) {
        if (requestCode == CAMERA_PERMISSION_REQUEST) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                mOpenCvCameraView.setCameraPermissionGranted();
            } else {
                String message = "Camera permission was not granted";
                Log.e(TAG, message);
                Toast.makeText(this, message, Toast.LENGTH_LONG).show();
            }
        } else {
            Log.e(TAG, "Unexpected permission request");
        }
    }

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

    @Override
    public void onResume() {
        super.onResume();
        if (!OpenCVLoader.initDebug()) {
            Log.d(TAG, "Internal OpenCV library not found. Using OpenCV Manager for initialization");
            OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION, this, mLoaderCallback);
        } else {
            Log.d(TAG, "OpenCV library found inside package. Using it!");
            mLoaderCallback.onManagerConnected(LoaderCallbackInterface.SUCCESS);
        }
    }

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

    @Override
    public void onCameraViewStarted(int width, int height) {
    }

    @Override
    public void onCameraViewStopped() {
    }

    //抓取摄像头数据,一帧一帧mat数据，传递给Native
    @Override
    public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
        Mat result = new Mat();

        adaptiveThresholdFromJNI(inputFrame.gray().getNativeObjAddr(), result.getNativeObjAddr());
        return result;
    }
    private native void adaptiveThresholdFromJNI(long input, long output);
}