Android SVM.predict not work properly

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I trained svm for detect painted and unpainted bubbles in picture. Opencv version is 3.4.1. It is work like a charm. Prediction (svm.predict()) work correct, like a charm too. Here is my code below.

 private static String pathNeg = "E:\\Android\\data\\negativo";
private static String pathPos = "E:\\Android\\data\\positivo";
private static String XML = "E:\\Android\\data\\model.xml";

static {
    System.load("E:/Android/opencv/build/java/x64/opencv_java340.dll");
}

public static void main(String[] args) {
    final HOGDescriptor hog = new HOGDescriptor(new Size(16, 16), new Size(8, 8), new Size(4, 4), new Size(4, 4), 9);
    Mat trainLabel = new Mat();
    Mat trainData = new Mat();

    for (File file : new File(pathPos).listFiles()) {
        if (file.getAbsolutePath().endsWith("jpg")) {
            final Mat img = Imgcodecs.imread(file.getAbsolutePath());
            MatOfFloat descriptors = new MatOfFloat();
            Imgproc.resize(img, img, new Size(16, 16));
            hog.compute(img, descriptors);
            Mat mat = descriptors.reshape(1, 1);
            trainData.push_back(mat);
            trainLabel.push_back(Mat.ones(new Size(1, 1), CvType.CV_32S));
        }
    }

    for (File file : new File(pathNeg).listFiles()) {
        if (file.getAbsolutePath().endsWith("jpg")) {
            Mat img = Imgcodecs.imread(file.getAbsolutePath());
            MatOfFloat descriptors = new MatOfFloat();
            Imgproc.resize(img, img, new Size(16, 16));
            hog.compute(img, descriptors);
            Mat mat = descriptors.reshape(1, 1);
            trainData.push_back(mat);
            trainLabel.push_back(Mat.zeros(new Size(1, 1), CvType.CV_32S));
        }
    }


    System.out.println("trainData rows:" + trainData.rows());
    System.out.println("trainLabel rows:" + trainLabel.rows());

    final SVM svm = SVM.create();
    svm.setKernel(SVM.RBF);
    trainData.convertTo(trainData, CvType.CV_32FC1);
    svm.trainAuto(trainData, Ml.ROW_SAMPLE, trainLabel);
    svm.save(XML);
}

Now i am using trained xml model in android app, but prediction svm.predict() not work properly. Not give right prediction. I am using Opencv Android sdk 3.4.0. And here is my code below

Uri uri = Uri.fromFile(new File(Environment.getExternalStorageDirectory(), "model.xml"));
    final SVM svm = SVM.load(uri.getPath());
    final HOGDescriptor hog = new HOGDescriptor(new Size(16, 16), new Size(8, 8), new Size(4, 4), new Size(4, 4), 9);
Mat answerROI = src.submat(rects.get(passedQuestionsCount));
                        MatOfFloat descriptors = new MatOfFloat();
                        Imgproc.resize(answerROI, answerROI, new Size(16, 16));
                        hog.compute(answerROI, descriptors);
                        Mat mat = descriptors.reshape(1, 1);
                        if (svm.predict(mat) > 0.0) {
                            bubbledRect = rects.get(passedQuestionsCount);
                        }