Null Pointer Debugging

Question

quick summary of what I'm trying to do.

Using shared preferences so that when a user watches a video a green tick will appear beside it to mark it as complete. Currently getting a null pointer error.

Basically there are two pages - main page and video page. When user lands on the main page the if statement should check the sharepreferences to see if they have already visited the video page. If they have it should display the completedTick imageView.

Please see the code and context below.

MAIN PAGE CODE SNIPPET:

 /**
 * Shared preferences variable which is used to store the userId which is captured at the login screen.
 */
private SharedPreferences loginPref, activityPref;   
private ImageView completedTick;
private Boolean activityCompleted;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

    loginPref = getContext().getSharedPreferences("loginPref", Context.MODE_PRIVATE);
    activityPref = getContext().getSharedPreferences("activityPref", Context.MODE_PRIVATE);
    activityCompleted = activityPref.getBoolean("activityCompleted", true);

    View view = inflater.inflate(R.layout.fragment_activities, container, false);

    initialiseRecyclerView(view);
    retrieveActivities();

    if(activityCompleted == false || activityCompleted == null ) {
        completedTick.setVisibility(view.INVISIBLE);
    }else{
        completedTick.setVisibility(View.VISIBLE);
    }

    return view;

}

@Override
public void onViewCreated(@NonNull final View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

}

/**
 * Method which is used to initialise the recycler view
 *
 * @param view
 */
private void initialiseRecyclerView(View view) {
    mRecyclerView = view.findViewById(R.id.recyclerViewActivities);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    EmptyAdapter emptyAdapter = new EmptyAdapter();
    mRecyclerView.setAdapter(emptyAdapter);
    completedTick = view.findViewById(R.id.completedTick);
}

VIDEO PAGE CODE SNIPPET:

private SharedPreferences activityPref;
private Boolean activityCompleted;


@Override
protected void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.youtube_layout);

    Log.d(TAG, "onCreateView: Starting");
    activityPref = getSharedPreferences("activityPref", MODE_PRIVATE);
    activityCompleted = activityPref.getBoolean("activityCompleted", true);

        getExtrasMethod();
        initialiseViews();
        setTextInViews();
        checkCompleteD();


 private void checkCompleteD() {

    if (activityCompleted) {
        SharedPreferences.Editor editor = activityPref.edit();
        activityCompleted = false;
        editor.putBoolean("activityCompleted", activityCompleted);
        editor.apply();

    }
}

The error is :

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setVisibility(int)' on a null object reference
        at com.example.fit.ActivitiesFragment.onCreateView(ActivitiesFragment.java:78)

UPDATE:

Made the suggedted changes

@Override
public void onViewCreated(@NonNull final View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    loginPref = getContext().getSharedPreferences("loginPref", Context.MODE_PRIVATE);
    activityPref = getContext().getSharedPreferences("activityPref", Context.MODE_PRIVATE);
    activityCompleted = activityPref.getBoolean("activityCompleted", true);

    completedTick = view.findViewById(R.id.completedTickImage);
    initialiseRecyclerView(view);
    retrieveActivities();

    if (activityCompleted == false || activityCompleted == null) {
        completedTick.setVisibility(View.INVISIBLE);
    } else {
        completedTick.setVisibility(View.VISIBLE);
    }
}

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setVisibility(int)' on a null object reference at com.example.feelingfit.ActivitiesFragment.onViewCreated(ActivitiesFragment.java:85)

Which is this line : completedTick.setVisibility(View.INVISIBLE);

`view.findViewById(R.id.completedTick)` is returning `null`. Figure out why. — Stephen C, May 30 '19 at 09:03
Try to declare the `findViewById` into the `onCreateView` and tell me if you re getting null or not. — Abedin.Zhuniqi, May 30 '19 at 09:05
Its still null, updated the question to show the updates I made to the code — androidnewbie, May 30 '19 at 09:39

coroutineDispatcher · Accepted Answer · 2019-05-30T09:59:01.633

5

First of all, your completedTick is null. Try putting the completedTick = view.findViewById(R.id.completedTick); in your OnViewCreated above this code:

if(activityCompleted == false || activityCompleted == null ) {
        completedTick.setVisibility(View.INVISIBLE);
    }else{
        completedTick.setVisibility(View.VISIBLE);
    }

And also, replace the view.INVISIBLE with View.INVISIBLE

Edit + Aditional Information:

If you occur again the NullPointerException please refer to this link.

Edit 2: Rewrite your code inside the onViewCreated method like this:

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

    return inflater.inflate(R.layout.fragment_activities, container, false);

}

@Override
public void onViewCreated(@NonNull final View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
 loginPref = getContext().getSharedPreferences("loginPref", Context.MODE_PRIVATE);
        activityPref = getContext().getSharedPreferences("activityPref", Context.MODE_PRIVATE);
        activityCompleted = activityPref.getBoolean("activityCompleted", true);

        initialiseRecyclerView(view);
        retrieveActivities();

        if(activityCompleted == false || activityCompleted == null ) {
            completedTick.setVisibility(View.INVISIBLE);
        }else{
            completedTick.setVisibility(View.VISIBLE);
        }
}

Edit number 3: Since it is crashing again on the same use case I assume your R.id.completedTickImage is not inside your fragment_activities

edited May 30 '19 at 09:59

answered May 30 '19 at 09:06

coroutineDispatcher

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1

I think this will do the job because his declarations need to be good. By the way brravo shqipe mvjen mire qe ka njerz qe punojn ne kete drejtim. – Abedin.Zhuniqi May 30 '19 at 09:12
1

that's my passion :) – coroutineDispatcher May 30 '19 at 09:12
I did exactly what you suggested but now it gives a null pointer on this line: if(activityCompleted == false || activityCompleted == null ) { – androidnewbie May 30 '19 at 09:17
1

ok I will update my answer now – coroutineDispatcher May 30 '19 at 09:18
Copied and pasted that in, still a null pointer......Im gonna scream :'( – androidnewbie May 30 '19 at 09:51
1

@androidnewbie please check my Edit number 3 – coroutineDispatcher May 30 '19 at 09:59
You're right.....its a recyclerView so the fragment_activitie sjust holds the recyclerview the content inside the view is in a different layout file....What do i do? – androidnewbie May 30 '19 at 10:03
1

Just pass your `ImageView` code inside the fragment that actually holds it. – coroutineDispatcher May 30 '19 at 10:05
This fragment does hold it but its a recyclerview so theres an adapter, the adapter holds the view for each recycler viewholder. – androidnewbie May 30 '19 at 10:10
1

If that ImageView is inside the `Recyclerview`, you should add that logic inside the `ViewHolder` class in your adapter. – coroutineDispatcher May 30 '19 at 10:11
1

Thank you Starvro, I managed to get it working with your help. Much appreicated. – androidnewbie May 30 '19 at 12:16
You are welcome. Good luck in the development world – coroutineDispatcher May 30 '19 at 12:52

score -1 · Answer 2 · edited May 30 '19 at 09:43

-1

Do the operation of CompleteTick.setVisibility inside onActivityCreated() method and also replace the view.INVISIBLE to View.INVISIBLE

edited May 30 '19 at 09:43

coroutineDispatcher

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answered May 30 '19 at 09:23

Porosh Mondal

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Null Pointer Debugging

2 Answers2