Face recognition using OpenCV in android?

wish help you to fix your issue Well, my colleagues and I did some investigation on face recognition last year, and these are some of ours considerations about using integrated recognition tools vs JavaCV (the Java bindings for OpenCV):
Please check below tutorials

I hope this helps . OpenCV indeed uses C and C++ (and also Python), however you can try and use a java wrapper for the opencv library. Here is a nice wrapper.

wish of those help The FaceDetector class doesn't do what you think it does. Specifically, it doesn't do Facial Recognition, but instead Facial Detection (hence the class name).

int maxNumFaces = 2; // Set this to whatever you want
FaceDetector fd = new FaceDetector(imageWidth,imageHeight,maxNumFaces);
Faces[] faces = new Faces[maxNumFaces];

try {
  int numFacesFound = fd.findFaces(image, faces);

  for (int i = 0; i < maxNumFaces; ++i) {
     Face face = faces[i];
     Log.d("Face " + i + " found with " + face.confidence() + " confidence!");
     Log.d("Face " + i + " eye distance " + face.eyesDistance());
     Log.d("Face " + i + " pose " + face.pose());
     Log.d("Face " + i + " midpoint (between eyes) " + face.getMidPoint());
  }
} catch (IllegalArgumentException e) {
  // From Docs:
  // if the Bitmap dimensions don't match the dimensions defined at initialization 
  // or the given array is not sized equal to the maxFaces value defined at 
  // initialization
}

it fixes the issue There are several reasons why the runtime might not be able to resolve the JNI function. Test these hypotheses:
The native code library didn't get bundled into your APK. Look inside the APK for it. The native code library is in the wrong directory of the APK. Again, look and see. The Java class got mangled by ProGuard so the names no longer match with the native library. Try turning off ProGuard. It should be off for debug builds. If your native code library is compiled for ARM but you're running in an x86 based Android emulator (or vice versa), it won't be able to load that library. Think of more hypotheses, then test them.

Any of those help After examining your code, I see a problem in how you collect labels. In this labels[i] = i; statement, you are setting one different label for each image you read. I think you have multiple images per person. Labels are numeric values (think of them like a code) assigned to each PERSON and not each IMAGE. If you had two persons with each having 3 images, label should be having values [0, 0, 0, 1, 1, 1].
Another possible problem you should check is that all images MUST be of the SAME size. This means every image you are reading in the loop must have same size AND also images used in predict must have same size. A good way to do that is by defining a fixed size, then resize every image you read to that fixed one.