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I’m new to fragments and I’m trying to take an activity and convert it to a fragment. A lot of the stuff I’m using needs Context and when I use getActivity() I get a log of warnings that it may return null and I’m not sure how to fix it. I read that I should attach the fragment to the activity somehow, but I’m not sure. I’m basically using one activity and going to have 4 fragments because I want to use a navigation drawer.
This is in the main activity for showing the fragments
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.nav_calendar:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new CalendarFragment()).commit();
break;
case R.id.nav_survey:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new SurveyFragment()).commit();
break;
case R.id.nav_forum:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new ForumFragment()).commit();
break;
case R.id.nav_logout:
logout();
break;
case R.id.nav_contact:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new ContactFragment()).commit();
break;
}
drawer.closeDrawer(GravityCompat.START);
return true;
}
And in the fragments onCreateView() I have this, I have a lot of methods and most of them use Context, I added the if statement because of the same warning and that seemed to work there but how should I take care of the rest on Context uses. I don’t see making an if statement for each time a good thing.
View view = inflater.inflate(R.layout.fragment_calendar, container, false);
if (getActivity() != null) {
((MainActivity) getActivity()).getSupportActionBar().setTitle(R.string.calendar);
}
AndroidThreeTen.init(getActivity());
initialBuild(view);
buildCalendarView();
setRecyclerView();
return view;
Edit
Related images
Also I tried without the @NonNull
Answer
See https://www.reddit.com/r/androiddev/comments/aklpz4/why_does_getactivity_in_fragment_might_be_null/.
You can use onActivityCreated() to access getActivity(), it won’t be null. I usually use onCreate() or onCreateView() to get getActivity(), but in some rare cases a fragment’s view can be created before hosting activity when an application starts (but I don’t remember this in real work).
In any case getActivity() is marked as Nullable, so you can compare it with null in any case.
UPDATE 1
See getActivity() returns null in Fragment function.
Between onAttach() and onDetach() you can get getActivity(), so save context in onAttach() and later use it in onCreateView().
UPDATE 2
Fragment:
private Activity activity;
@Override
public void onAttach(Context context) {
super.onAttach(activity);
if (context instanceof Activity){
activity = (Activity) context;
}
}
@Override
public void onDetach() {
super.onDetach();
activity = null;
}
@Override
public void onCreateView() {
// Use activity here.
}
UPDATE 3
Sorry,
@Override
public void onAttach(@NonNull Context context) {
super.onAttach(context);
if (context instanceof Activity){
activity = (Activity) context;
}
}