android : camera doesn’t open in marshmallow

So, I accomplished my task like as below:

For Checking permission I created a separate class as below:

public class MarshMallowPermission {

    public static final int RECORD_PERMISSION_REQUEST_CODE = 1;
    public static final int EXTERNAL_STORAGE_PERMISSION_REQUEST_CODE = 2;
    public static final int CAMERA_PERMISSION_REQUEST_CODE = 3;
    Activity activity;

    public MarshMallowPermission(Activity activity) {
        this.activity = activity;
    }

    public boolean checkPermissionForRecord(){
        int result = ContextCompat.checkSelfPermission(activity, Manifest.permission.RECORD_AUDIO);
        if (result == PackageManager.PERMISSION_GRANTED){
            return true;
        } else {
            return false;
        }
    }

    public boolean checkPermissionForExternalStorage(){
        int result = ContextCompat.checkSelfPermission(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE);
        if (result == PackageManager.PERMISSION_GRANTED){
            return true;
        } else {
            return false;
        }
    }

    public boolean checkPermissionForCamera(){
        int result = ContextCompat.checkSelfPermission(activity, Manifest.permission.CAMERA);
        if (result == PackageManager.PERMISSION_GRANTED){
            return true;
        } else {
            return false;
        }
    }

    public void requestPermissionForRecord(){
        if (ActivityCompat.shouldShowRequestPermissionRationale(activity, Manifest.permission.RECORD_AUDIO)){
           Toast.makeText(activity, "Microphone permission needed for recording. Please allow in App Settings for additional functionality.", Toast.LENGTH_LONG).show();
        } else {
            ActivityCompat.requestPermissions(activity,new String[]{Manifest.permission.RECORD_AUDIO},RECORD_PERMISSION_REQUEST_CODE);
        }
    }

    public void requestPermissionForExternalStorage(){
        if (ActivityCompat.shouldShowRequestPermissionRationale(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE)){
            Toast.makeText(activity, "External Storage permission needed. Please allow in App Settings for additional functionality.", Toast.LENGTH_LONG).show();
        } else {
            ActivityCompat.requestPermissions(activity,new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},EXTERNAL_STORAGE_PERMISSION_REQUEST_CODE);
        }
    }

    public void requestPermissionForCamera(){
        if (ActivityCompat.shouldShowRequestPermissionRationale(activity, Manifest.permission.CAMERA)){
            Toast.makeText(activity, "Camera permission needed. Please allow in App Settings for additional functionality.", Toast.LENGTH_LONG).show();
        } else {
            ActivityCompat.requestPermissions(activity,new String[]{Manifest.permission.CAMERA},CAMERA_PERMISSION_REQUEST_CODE);
        }
    }
}

Then, for getting

...
MarshMallowPermission marshMallowPermission = new MarshMallowPermission(this);
...

public void getPhotoFromCamera() {

    if (!marshMallowPermission.checkPermissionForCamera()) {
        marshMallowPermission.requestPermissionForCamera();
    } else {
        if (!marshMallowPermission.checkPermissionForExternalStorage()) {
            marshMallowPermission.requestPermissionForExternalStorage();
        } else {
            Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
            File mediaStorageDir = new File(
                    Environment.getExternalStorageDirectory()
                            + File.separator
                            + getString(R.string.directory_name_corp_chat)
                            + File.separator
                            + getString(R.string.directory_name_images)
            );

            if (!mediaStorageDir.exists()) {
                mediaStorageDir.mkdirs();
            }

            String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss",
                    Locale.getDefault()).format(new Date());
            try {
                mediaFile = File.createTempFile(
                        "IMG_" + timeStamp,  /* prefix */
                        ".jpg",         /* suffix */
                        mediaStorageDir      /* directory */
                );
                takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(mediaFile));
                startActivityForResult(takePictureIntent, PICK_FROM_CAMERA);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}