Navigation Drawer, how to change Header?

Question

Android

Android studio has a template for creating Navigation Drawer. I need to change its title programmatically. I have an application when using the methods:

twNavBarName = (TextView) findViewById(R.id.nav_header_tw_name);
twNavBarEmail = (TextView) findViewById(R.id.nav_header_tw_email);
twNavBarName.setText("fdfs");

crashes and logs nothing at all. How to change the headers with the name and email, in the figure they are shown at numbers 1 and 2.