How to determine the number of Chessboard corners found in CameraCalibration

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I am trying to calibrate mobile camera, by writing a code in OpenCv4Android. I am trying to find out the chessboard corners using the function -

public static boolean findChessboardCorners(Mat image, Size patternSize, MatOfPoint2f corners, int flags)

I am using this method in my code. The problem i am facing is, For every frame the return value of this method is coming false, even if the chessboard corners are properly put into the camera view. i want to debug my application, to see how many chessboard corners have been determined.

Can you please guide me in performing the action, also please guide me in performing the camera calibration for Android mobile using OpenCv4Android. Can you please suggest me some blog which has tried to implement this in OpenCv4Android ? Or any sample code.

Thanks in Advance !!