avoid fragment list data duplicating on recyclerView - android

I had some fragments switch on one activity.
I found a issue is that when i turn back the fragment , it will show duplicate data.
I try to clear the arrayList data to solve it.
But i want to know more smart way.
Is any possible to avoid this issue for duplicate data ?
My fragment code:
public class Vaccine extends Fragment {
private List<VaccineItem> vaccineList = new ArrayList<>();
private VaccineAdapter vaccineAdapter;
private RecyclerView recyclerVaccine;
public Vaccine() {
}
public static Vaccine newInstance() {
return new Vaccine();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.vaccine_fragment_, container, false);
recyclerVaccine = (RecyclerView) view.findViewById(R.id.recyclerVaccine);
recyclerVaccine.setLayoutManager(new LinearLayoutManager(getActivity()));
vaccineList.clear();// i use it to slove the problem.--------------
testData();
vaccineAdapter = new VaccineAdapter(getActivity(), vaccineList);
recyclerVaccine.setAdapter(vaccineAdapter);
vaccineAdapter.notifyDataSetChanged();
return view;
}
private void testData(){
VaccineItem vaccineItem=new VaccineItem("Data1");
vaccineList.add(vaccineItem);
vaccineItem=new VaccineItem("Data2");
vaccineList.add(vaccineItem);
}
}


Try with this
View view; // declare this globally
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if(view == null){ // initialize if view is null
view = inflater.inflate(R.layout.vaccine_fragment_, container, false);
recyclerVaccine = (RecyclerView) view.findViewById(R.id.recyclerVaccine);
recyclerVaccine.setLayoutManager(new LinearLayoutManager(getActivity()));
vaccineList.clear();// i use it to slove the problem.--------------
testData();
vaccineAdapter = new VaccineAdapter(getActivity(), vaccineList);
recyclerVaccine.setAdapter(vaccineAdapter);
vaccineAdapter.notifyDataSetChanged();
}
return view;
}


Call testData() in your constructor, not in onCreateView.


The reason you are getting duplicate data is because you are calling testData() when fragment view is created. This adds same items everytime your fragment is recreated. There is nothing wrong with clearing the list though.

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use its like,
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So in your case, the layout class_view is bound to the rootView. But when you just write findViewById, it means that this.findViewById. And this is the scope you're in, which is the Fragment in your case. However, I don't think a Fragment has that capability. So you should refer to the rootView to retrieve your views.
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Fragments don't have a findViewById() method like Activity, so you have to call the method of the root view of the fragment. Try doing rootView.findViewById(R.id.classList) instead.

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You can use getActivity().findByView() from the Fragment if you want to have access to the layout elements. Alternatively, you can just put the findByView() call in the main Activity.

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