Calling SharedPrefences in Fragments - android-studio

Question

I have a class with the name of SharePrefManager. Here is the code
package com.example.lms02;
public class SharedPrefManager {
private static final String SHARED_PREF_NAME = "volleyregisterlogin";
private static final String KEY_USERNAME = "keyusername";
private static final String KEY_EMAIL = "keyemail";
private static final String KEY_GENDER = "keygender";
private static final String KEY_ID = "keyid";
private static final String KEY_STDID = "keystdid";
private static final String KEY_USER_STATUS = "keyuserstatus";
private static SharedPrefManager mInstance;
private static Context ctx;
private SharedPrefManager(Context context) {
ctx = context;
}
public static synchronized SharedPrefManager getInstance(Context context) {
if (mInstance == null) {
mInstance = new SharedPrefManager(context);
}
return mInstance;
}
//this method will store the user data in shared preferences
public void userLogin(User user) {
SharedPreferences sharedPreferences = ctx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putInt(KEY_ID, user.getId());
editor.putString(KEY_STDID,user.getStdid());
editor.putString(KEY_USERNAME, user.getName());
editor.putString(KEY_EMAIL, user.getEmail());
editor.putString(KEY_GENDER, user.getGender());
editor.putString(KEY_USER_STATUS, user.getStatus());
editor.apply();
}
//this method will checker whether user is already logged in or not
public boolean isLoggedIn() {
SharedPreferences sharedPreferences = ctx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
return sharedPreferences.getString(KEY_USERNAME, null) != null;
}
//this method will give the logged in user
public User getUser() {
SharedPreferences sharedPreferences = ctx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
return new User(
sharedPreferences.getInt(KEY_ID, -1),
sharedPreferences.getString(KEY_STDID, null),
sharedPreferences.getString(KEY_USERNAME, null),
sharedPreferences.getString(KEY_EMAIL, null),
sharedPreferences.getString(KEY_GENDER, null),
sharedPreferences.getString(KEY_USER_STATUS, null)
);
}
//this method will logout the user
public void logout() {
SharedPreferences sharedPreferences = ctx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.clear();
editor.apply();
ctx.startActivity(new Intent(ctx, LoginActivity.class));
}
}
I am using Fragments. Here is the code of my Fragment
public class HomeFragment extends Fragment {
TextView txtvwuserid;
User user = SharedPrefManager.getInstance(getContext()).getUser();
public HomeFragment() {
// Required empty public constructor
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_home, container, false);
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
txtvwuserid = getActivity().findViewById(R.id.txtvwstdid);
txtvwuserid.setText("Hy");
}
}
The problem occurs in HomeFragment here
User user = SharedPrefManager.getInstance(getContext()).getUser();
The Error shown is:
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences
android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
My Problem is how can i access the values of SharedPrefManager and what does the error means

Answer 1

Problem Solved:
According to the Fragment Life Cycle. we have to place all of our code after the creation of Fragment. What I was doing wrong is Declaring the User object before creation of fragment. Placing it like
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
user = SharedPrefManager.getInstance(getActivity()).getUser(); //Placing here
}
It Worked For me. Cheers...!!!