Can not perform this action after onSaveInstanceState Android

问题

I am getting java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState . When I did fragmentManager.popBackStack(). This crash is random . I am not overriding onSaveInstanceState() in my activity.

       Navigator.post(new Runnable() {
            @Override
            public void run() {
                if (actRef != null && actRef.get() != null) {
                    if (isLastFragment()) {
                        finish();
                    } else {
                        if (fragMngr != null) {
                            try {
                                fragMngr.popBackStack();//crashing in this line
                                /**
                                 * check if it is last fragment
                                 */
                                if (isLastFragment()) {
                                    finish();
                                }
                            } catch (IllegalStateException ignored) {
                                ignored.printStackTrace();
                            }
                        }
                    }
                }
            }
        });

来源：https://stackoverflow.com/questions/49017470/can-not-perform-this-action-after-onsaveinstancestate-android