授予用户权限时，应用程序崩溃

Question

嗨我有一个扫描QR码的应用程序，因此它需要相机权限。我有一个SurfaceView，我在其中显示相机预览。 在清单中我添加了：<uses-permission android:name="android.permission.CAMERA"></uses-permission>

在我的扫描片段中，我有这段代码：

public class Tab2Scan extends Fragment {

private static final int PERMS_REQUET_CODE = 123;
// QREader
private SurfaceView mySurfaceView;
private QREader qrEader;
Context thisContext;

View rootView;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    rootView = inflater.inflate(R.layout.tab2scan, container, false);


    if(hasPermissions())
    {
        startReading();
    }
    else
    {
        requestPerms();
    }


    return rootView;
}

private boolean hasPermissions()
{
    int res = 0;

    String [] permissions = new String[]{Manifest.permission.CAMERA};

    for (String perms : permissions)
    {
        res = checkCallingOrSelfPermission(getContext(),perms);
        if(!(res == PackageManager.PERMISSION_GRANTED))
        {
            return false;
        }
    }
    return true;
}

private void requestPerms()
{
    String [] permissions = new String[]{Manifest.permission.CAMERA};
    if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
    {
        requestPermissions(permissions, PERMS_REQUET_CODE);
    }
}

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults)
{
    boolean allowed = true;

    switch (requestCode)
    {
        case PERMS_REQUET_CODE:

            for(int res:grantResults)
            {
                allowed = allowed && (res == PackageManager.PERMISSION_GRANTED);
            }
            break;

        default:
            allowed = false;
            break;
    }

    if(allowed)
    {
        startReading();
    }
    else
    {
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
        {
            if(shouldShowRequestPermissionRationale(Manifest.permission.CAMERA))
            {
                Toast.makeText(thisContext, "Abilita l'accesso alla fotocamera", Toast.LENGTH_SHORT).show();
            }
        }

    }
}

private void startReading()
{
    getActivity().getWindow().setSoftInputMode(
            WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);

    thisContext = getContext();

    mySurfaceView = (SurfaceView) rootView.findViewById(R.id.camera_view);
    // Init QREader
    // ------------
    qrEader = new QREader.Builder(thisContext, mySurfaceView, new QRDataListener() {
        @Override
        public void onDetected(final String data) {

            //qrEader.stop();
            Intent intent = new Intent(getActivity(), ShowData.class);
            intent.putExtra("variabile", data);
            startActivity(intent);
            getActivity().finish();
            //Toast.makeText(thisContext, result.getContents(),Toast.LENGTH_LONG).show();

            Log.d("QREader", "Value : " + data);
        }
    }).facing(QREader.BACK_CAM)
            .enableAutofocus(true)
            .height(mySurfaceView.getHeight())
            .width(mySurfaceView.getWidth())
            .build();

    qrEader.start();
}

@Override
public void onResume() {
    super.onResume();

    // Init and Start with SurfaceView
    // -------------------------------
    qrEader.initAndStart(mySurfaceView);
    qrEader.start();
}

@Override
public void onPause() {
    super.onPause();

    // Cleanup in onPause()
    // --------------------
    qrEader.releaseAndCleanup();
}

}

当我发布片段时，它崩溃说：java.lang.NullPointerException: Attempt to invoke virtual method 'void github.nisrulz.qreader.QREader.initAndStart(android.view.SurfaceView)' on a null object reference

任何人都知道如何解决？谢谢！