Going to Main Activity from fragment - android-studio

Question

I implemented a navigation drawer and had used fragments. Now i can switch to fragments from the drawer menu. But when i press back, my app closes from that fragment and don't know how to go back to the main activity.
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
int id = item.getItemId();
displaySelectedScreen(id);
return true;
}
private void displaySelectedScreen(int id) {
Fragment frag = null;
switch (id) {
case R.id.trigger:
break;
case R.id.setup:
if (android.os.Build.VERSION.SDK_INT >= 21) {
getWindow().setStatusBarColor(Color.parseColor("#7B1FA2"));
}
getSupportActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#8E24AA")));
frag = new SettingsF();
break;
case R.id.recordings:
if (android.os.Build.VERSION.SDK_INT >= 21) {
getWindow().setStatusBarColor(Color.parseColor("#4E342E"));
}
getSupportActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#8D6E63")));
break;
case R.id.howto:
if (android.os.Build.VERSION.SDK_INT >= 21) {
getWindow().setStatusBarColor(Color.parseColor("#7B1FA2"));
}
getSupportActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#8E24AA")));
break;
case R.id.about:
if (android.os.Build.VERSION.SDK_INT >= 21) {
getWindow().setStatusBarColor(Color.parseColor("#7B1FA2"));
}
getSupportActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#8E24AA")));
break;
case R.id.email_us:
if (android.os.Build.VERSION.SDK_INT >= 21) {
getWindow().setStatusBarColor(Color.parseColor("#7B1FA2"));
}
getSupportActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#8E24AA")));
break;
}
if (frag != null) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_main, frag);
ft.addToBackStack(ft.getClass().getSimpleName()).commit();
}
DrawerLayout drawer = findViewById(R.id.drawer);
drawer.closeDrawer(GravityCompat.START);
}
And here is the setting fragment only:
public class SettingsF extends ListFragment {
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_settings, container, false);
String[] datasource = {"Trusted Contacts", "Custom Text Set-Up"};
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(), R.layout.rowlayout, R.id.txtitems, datasource);
setListAdapter(adapter);
setRetainInstance(true);
return rootView;
}
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
getActivity().setTitle("Context Set-Up");
}
public void onListItemClick(ListView l, View view, int position, long id) {
ViewGroup viewGroup = (ViewGroup) view;
TextView tv = (TextView) viewGroup.findViewById(R.id.txtitems);
Toast.makeText(getActivity(), tv.getText().toString(), Toast.LENGTH_LONG).show();
}
#Override
public void onResume() {
getView().setFocusableInTouchMode(true);
getView().requestFocus();
getView().setOnKeyListener( new View.OnKeyListener()
{
#Override
public boolean onKey( View v, int keyCode, KeyEvent event )
{
if( keyCode == KeyEvent.KEYCODE_BACK )
{
//Already Used Intent, doesn't work
return true;
}
return false;
}
} );
super.onResume();
}
}
I updated the question. I already used addToBackStack(), then overrided the method onResume() but still the app terminates when pressing the back button.
I'm really that new to this, so don't misunderstand me what did i implemented throughout the codes.
Thanks In Advance

Answer 1

for Hardware backbutton
add this code in onResume method in fragment
//You need to add the following line
fragment.getView().setFocusableInTouchMode(true);
fragment.getView().requestFocus();
fragment.getView().setOnKeyListener( new OnKeyListener()
{
#Override
public boolean onKey( View v, int keyCode, KeyEvent event )
{
if( keyCode == KeyEvent.KEYCODE_BACK )
{
//here use intent to call mainActivity
return true;
}
return false;
}
} );
hope this will help you

Answer 2

Add this line after ft.replace():
ft.addToBackStack(null);
This line will make it so that each time you select an item from the navigation drawer, a history of fragments is built up. Then when you press the back button, you'll go back through the history. If you have no history items, the app will close.
A more sophisticated implementation might use a name argument (like "FragA" or "FragB") instead of null as the argument for addToBackStack(), and then check to see if your fragment already exists in the back stack instead of always opening a new one. That way if you went A->B->A->B->A->B you wouldn't have three copies of A and two copies of B in the history.