navCehua. SetNavigationItemSelectedListener (new NavigationView OnNavigationItemSelectedListener () {
@ Override 
Public Boolean onNavigationItemSelected (@ NonNull MenuItem MenuItem) {
The switch (menuItem getItemId ()) {
Case R.i d.i t_Upload: 
TvTitle. SetText (" upload the wrong topic "); 
SwitchFrag (fr_u); 
Toast. MakeText (MainActivity. This menuItem. GetTitle (), toString (), Toast. LENGTH_SHORT), show (); 
break; 
Case R.i d.i t_Calendar: 
TvTitle. SetText (" exam calendar "); 
SwitchFrag (fr_c); 
break; 
Case R.i d.i t_Text: 
TvTitle. SetText (" wrong topic test "); 
SwitchFrag (fr_t); 
Toast. MakeText (MainActivity. This menuItem. GetTitle (), toString (), Toast. LENGTH_SHORT), show (); 
break; 
Case R.i d.i t_Analyse: 
TvTitle. SetText (" atlas analysis "); 
SwitchFrag (fr_a); 
break; 
} 

//navCehua. GetMenu (). The clear (); 
//navCehua. InflateMenu (R.m emu. Cehua_menu); 
//navCehua. GetMenu (.) findItem (menuItem. GetItemId ()). SetChecked (true); 
The drawer. CloseDrawer (GravityCompat. START); 
return true; 
} 
}); 

} 


//conversion fragments 
Public void SwitchFrag (fragments targetFragment) {

FragmentTransaction transaction=getSupportFragmentManager (). The beginTransaction (); 
//if the Fragment is not to add, add, or show 
if(! TargetFragment. IsAdded ()) {

Transaction. Hide (currentFragment). The add (R.i d.d l_cebian, targetFragment), commit (); 
} 
The else {
Transaction. Hide (currentFragment.) the show (targetFragment). The commit (); 
} 
CurrentFragment=targetFragment; 
}