Actions in onActivityResult and "Error Can not perform this action after onSaveInstanceState"

Implementing an app where the user can log in I have the following situation: If the user is logged in perform the action else start the login activity for result and if the result is Activity.RESULT_OK do the action.

My problem is that the action to perfom is to show a DialogFragment, but calling

DialogFragment newFragment = MyDialogFragment.newInstance(mStackLevel);
newFragment.show(ft, "dialog")

in the onActivityResult callback throws an exception:

Caused by: java.lang.IllegalStateException:  
Can not perform this action after onSaveInstanceState

So how can I solve this? I'm thinking in raising a flag there and show the dialog in the onResume but I see this solution a little dirty

Edit: Added more code (Im following this example for showing the DialogFragment

When the action is requested by the user:

... 
if (!user.isLogged()){
 startActivityForResult(new Intent(cnt, Login.class), REQUEST_LOGIN_FOR_COMMENT);
}

In the same fragment

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == REQUEST_LOGIN_FOR_COMMENT && resultCode == Activity.RESULT_OK) {
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        DialogFragment newFragment = MyDialogFragment.newInstance();
        newFragment.show(ft, "dialog")
    }
}

And if the user logs in the Login activity calls;

setResult(Activity.RESULT_OK);
finish();

Best thing I've come up with is to not use .show() but rather do this.

CheckinSuccessDialog dialog = new CheckinSuccessDialog();
//dialog.show(getSupportFragmentManager(), null);
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(dialog, null);
ft.commitAllowingStateLoss();

Here is the workaround that works fine for me.

private void alert(final String message) {
    Handler handler = new Handler(Looper.getMainLooper());
    handler.post(new Runnable() {
        public void run() {
            AlertDialogFragment alertDialogFragment = AlertDialogFragment.newInstance(message);
            alertDialogFragment.show(getFragmentManager(), ALERT_DIALOG_FRAGMENT);
        }
    });        
}

If using a DialogFragment, the only thing that worked for me was to dismiss the Fragment with dissmissAllowingStateLoss()

I simply check whether an activity is being destroyed.

if (!getActivity().isFinishing()) {
    DialogFragment fragment = MyFragment.newInstance();
    fragment.show(getActivity().getSupportFragmentManager(), MyFragment.TAG);
}

See also https://stackoverflow.com/a/41813953/2914140. In DialogFragment write:

override fun show(manager: FragmentManager?, tag: String?) {
    try {
        val ft = manager?.beginTransaction()
        ft?.add(this, tag)
        ft?.commitAllowingStateLoss()
    } catch (ignored: IllegalStateException) {
    }
}