does textview in fragment needs to be declared static

Question

i have started to learn android recently and i was looking at a fragment example in a video tutorial in the tutorial they haven't made the textview static but when i tried to implement fragment with some changes in the code i started to get null pointer exception my code looks like this

public class BlankFragment2 extends Fragment {

TextView tv;

public BlankFragment2() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_blank_fragment2, container, false);
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    tv= (TextView) getActivity().findViewById(R.id.txt2);
}



public void setName(String name){
    //tv=(TextView)getActivity().findViewById(R.id.txt2);
    if(tv == null){
        System.out.println("tv is null");
    }
    tv.setText("Hi "+name);
}
}

i am getting null pointer exception at settext unless i make the textview static can someone please explain why

this is not duplicate of what is NPE i know what NPE is and why it shows up my question here is that after initializing the textview in onActivityCreated why it is null again in setname function

@ADM this is definitely not a duplicate of what is NPE i know why NPE comes, i have updated the question to explain the problem in better way — pawn doe, Apr 18 '18 at 09:52
This does not make any difference Ultimately you are accessing a Null object which will gives you NPE. The root cause is `getActivity()` points to parent `Activity` and your view is part of fragment not activity. — ADM, Apr 18 '18 at 10:02
@ADM i also tried View view = getView(); then view.findViewById(R.id.txt2) still getting NPE — pawn doe, Apr 18 '18 at 10:04
Just use the solution right below. Read [Creating a Fragment](https://developer.android.com/guide/components/fragments.html#Creating). — ADM, Apr 18 '18 at 10:06

IntelliJ Amiya · Answer 1 · 2018-04-18T09:18:15.047

1

NullPointerException is thrown when an application attempts to use an object reference that has the null value.

FYI

You should return VIEW's object
Check findViewById(R.id.txt2 . Make sure you this ID present in XML.

Don't

tv= (TextView) getActivity().findViewById(R.id.txt2);

Do

 tv= (TextView) view.findViewById(R.id.txt2);

Try this way

     @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
             View view= inflater.inflate(R.layout.fragment_blank_fragment2, container, false);
             tv= (TextView) view.findViewById(R.id.txt2);
            return view;
        }

edited Apr 18 '18 at 09:18

answered Apr 18 '18 at 08:50

IntelliJ Amiya

74,896
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i tried, this also gives NPE – pawn doe Apr 18 '18 at 08:58
What's wrong with [getActivity().findViewById()](https://developer.android.com/reference/android/app/Activity.html#findViewById(int)) ? – 2Dee Apr 18 '18 at 08:58
@pawndoe check `findViewById(R.id.txt2);` . Id tx2 is valid or not? – IntelliJ Amiya Apr 18 '18 at 08:59
@pawndoe After change `Clean-Rebuild and run` – IntelliJ Amiya Apr 18 '18 at 09:04
did that still getting NPE – pawn doe Apr 18 '18 at 09:40
@IntelliJAmiya id txt2 is valid since making textview static solves NPE. problem is that after initializing textview in onActivityCreated it is again null in setname method – pawn doe Apr 18 '18 at 09:44
@pawndoe oh...sloppy mistake – IntelliJ Amiya Apr 18 '18 at 09:44
@IntelliJAmiya can you explain why it is null again in setname – pawn doe Apr 18 '18 at 09:48
@pawndoe I assume `String name` is null. Debug please. – IntelliJ Amiya Apr 18 '18 at 09:50
@IntelliJAmiya i tried to sysout name, it is not null instead the if(tv==null) in showname method returns true – pawn doe Apr 18 '18 at 09:55
@pawndoe you should check `if (TextUtils.isEmpty(name))` – IntelliJ Amiya Apr 18 '18 at 09:57
@IntelliJAmiya i suppose that would check if the name is empty or not but the problem here is that textview tv is null in setname method so calling settext on tv return NPE so i wanted to know why tv is null after i have initialized it in onActivityCreated method – pawn doe Apr 18 '18 at 10:03

score 1 · Answer 2 · edited Apr 18 '18 at 09:07

1

Not getActivity().findViewById(), it must be view.findViewById() because Activity.findViewById() will look for a View in the Activity layout, whereas view.findViewById() will look for the View in the Fragment layout.

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View inflatedView = inflater.inflate(R.layout.fragment_blank_fragment2, container, false);
    return inflatedView;
}

And in onViewCreated you can initialise your TextView

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    // here goes your intialisation using view
    tv= (TextView) view.findViewById(R.id.txt2);
}

Make sure you have a TextView with the id txt2 in fragment_blank_fragment2.xml

edited Apr 18 '18 at 09:07

2Dee

8,609
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answered Apr 18 '18 at 08:52

Vivek_Neel

1,343
1
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What's wrong with [getActivity().findViewById()](https://developer.android.com/reference/android/app/Activity.html#findViewById(int)) ? – 2Dee Apr 18 '18 at 08:56
` getActivity().findViewById() ` will search for the id in activity layout. will give NPE – Vivek_Neel Apr 18 '18 at 08:59
this is also giving NPE – pawn doe Apr 18 '18 at 09:00
1

Make sure that `R.id.txt2` exists in `R.layout.fragment_blank_fragment2` – Vivek_Neel Apr 18 '18 at 09:01
1

You should put that in your answer is what I mean... Hopefully you'll like my edit ;) Good answer though ! – 2Dee Apr 18 '18 at 09:08
since making the textview static solves the problem means that txt2 is present and accessible – pawn doe Apr 18 '18 at 09:27

score 0 · Answer 3 · answered Apr 18 '18 at 11:05

0

Sorry guys it was a stupid mistake on my side, in my mainactivity i wrote

BlankFragment2 frag2 = new BlankFragment2();
    frag2.setName(name);

i corrected it by writing

BlankFragment2 frag2=(BlankFragment2)getFragmentManager().findFragmentById(R.id.frag2);
    fragb.setName(name);

now it is working

answered Apr 18 '18 at 11:05

pawn doe

53
5

Glad to see you fixed that. – IntelliJ Amiya Apr 18 '18 at 12:01

does textview in fragment needs to be declared static

3 Answers3