onClick event in navigation drawer

Add NavigationItemSelectedListener event to nav_view

NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

Implement your Activity with NavigationView.OnNavigationItemSelectedListener

and add this code for click item

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_camera) {
        // Handle the camera action
    } else if (id == R.id.nav_gallery) {

    } else if (id == R.id.nav_slideshow) {

    } else if (id == R.id.nav_manage) {

    } else if (id == R.id.nav_share) {

    } else if (id == R.id.nav_send) {

    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

You need to add implements NavigationView.OnNavigationItemSelectedListener

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener

and add method

@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
    // Handle navigation view item clicks here.
    switch (item.getItemId()) {

       case R.id.nav_maths: {
      //do somthing
            break;
        }  
    }
    //close navigation drawer
    mDrawerLayout.closeDrawer(GravityCompat.START);
    return true;
}

method to set Listener

private void setNavigationViewListener() {
    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}

call method in onCreate()

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setNavigationViewListener()
}