i have SharedPrefManger class which save user information and retrieve data but when i use this into fragment return null pointer exception
package com.example.e_learning.storage;
import android.content.Context;
import android.content.SharedPreferences;
import com.example.e_learning.jsondata.StudentData;
import com.example.e_learning.pojo.StudentModel;
public class SharedPrefManger {
private static SharedPrefManger INSTANCE;
private Context context;
private static final String SHARED_PREF_NAME = "MySharedPref";
public SharedPrefManger(Context context) {
this.context = context;
}
public static SharedPrefManger getINSTANCE(Context context) {
if (INSTANCE == null)
INSTANCE = new SharedPrefManger(context);
return INSTANCE;
}
public void saveUser(StudentData data) {
SharedPreferences preferences = context.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();
editor.putInt("id", data.getId());
editor.putString("email", data.getEmail());
editor.putString("name", data.getName());
editor.putString("level", data.getLevel());
editor.apply();
}
public boolean isLoggedIn() {
SharedPreferences preferences = context.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
return preferences.getInt("id", -1) != -1;
}
public StudentData getUser() {
SharedPreferences preferences = context.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
return new StudentData(
preferences.getInt("id", -1),
preferences.getString("name", null),
preferences.getString("email", null),
preferences.getString("level", null)
);
}
public void clear(){
SharedPreferences preferences = context.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();
editor.clear();
editor.apply();
}
}
and i have a fragment which i want to retrieve the user into it but when i call getUser Id return null
this is my fragment
package com.example.e_learning.ui.fragments.announcement;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.databinding.DataBindingUtil;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.ViewModelProvider;
import androidx.recyclerview.widget.LinearLayoutManager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;
import com.example.e_learning.R;
import com.example.e_learning.databinding.FragmentAnnouncementBinding;
import com.example.e_learning.jsondata.AnnouncementsData;
import com.example.e_learning.storage.SharedPrefManger;
import java.util.ArrayList;
/**
* A simple {@link Fragment} subclass.
*/
public class AnnouncementFragment extends Fragment {
private FragmentAnnouncementBinding binding;
private AnnouncementsViewModel announcementsViewModel;
public AnnouncementFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
binding = DataBindingUtil.inflate(inflater, R.layout.fragment_announcement, container, false);
View view = binding.getRoot();
return view;
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
AnnouncementAdapter announcementAdapter = new AnnouncementAdapter();
binding.announcementRecycler.setLayoutManager(new LinearLayoutManager(getContext()));
binding.announcementRecycler.setAdapter(announcementAdapter);
announcementsViewModel.getStudentId().setValue(SharedPrefManger.getINSTANCE(this.getActivity()).getUser().getId());
announcementsViewModel = new ViewModelProvider(requireActivity()).get(AnnouncementsViewModel.class);
announcementsViewModel.getAnnouncements();
announcementsViewModel.announcementsModelMutableLiveData.observe(getViewLifecycleOwner(), announcementsModel -> {
if (announcementsModel.getStatus()) {
announcementAdapter.setList((ArrayList<AnnouncementsData>) announcementsModel.getData());
} else if (!announcementsModel.getStatus()) {
Toast.makeText(getContext(), announcementsModel.getError(), Toast.LENGTH_SHORT).show();
}
});
}
}
this line return null Pointer Exception
announcementsViewModel.getStudentId().setValue(SharedPrefManger.getINSTANCE(this.getActivity()).getUser().getId());
how i can retrieve userdata into this fragment? this class works good with other activities
You must initialize the announcementsViewModel
first before using it so you need to move this line
announcementsViewModel = new ViewModelProvider(requireActivity()).get(AnnouncementsViewModel.class);
before this
announcementsViewModel.getStudentId().setValue(SharedPrefManger.getINSTANCE(this.getActivity()).getUser().getId());
Create the object of the class Shared Preference, having constructor. and where you want to get it, just call the constructor with new keyword and that pref name method. Like: new PrefManager(getActivity).getData();
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