Android-handle-permission-request.java

 @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode) {
            case REQUEST_CAMERA: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    //Permission was granted. Now you can call your method to open camera, fetch contact or whatever
                    openCamera();
                } else {
                    // Permission was denied.......
                    // You can again ask for permission from here
                    Toast.makeText(this, "Permission Denied", Toast.LENGTH_SHORT).show();
                }
                break;
            }

        }
    }