Getting view id of Button to change properties of fragment view component

Question

I am trying to reuse a View(.xml file) which is displayed through the use of a fragment. The problem is, since I'm reusing the view, I need to rename the TextView's text value based on the lesson name selected by user.

public class StudentMultiplicationFragment extends Fragment{

    Button btnLesson1, btnLesson2, btnLesson3, btnLesson4, btnLesson5, btnLesson6;

    public StudentMultiplicationFragment() {
        // Required empty public constructor

    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.frag_studentmultiplication, container, false);
        btnLesson1 = view.findViewById(R.id.multiplication_lesson1);
        btnLesson2 = view.findViewById(R.id.multiplication_lesson2);
        btnLesson3 = view.findViewById(R.id.multiplication_lesson3);
        btnLesson4 = view.findViewById(R.id.multiplication_lesson4);
        btnLesson5 = view.findViewById(R.id.multiplication_lesson5);
        btnLesson6 = view.findViewById(R.id.multiplication_lesson6);

        btnLesson1.setOnClickListener(new goToLessonStartFragment(btnLesson1.getText().toString()));
        btnLesson2.setOnClickListener(new goToLessonStartFragment(btnLesson2.getText().toString()));
        btnLesson3.setOnClickListener(new goToLessonStartFragment(btnLesson3.getText().toString()));
        btnLesson4.setOnClickListener(new goToLessonStartFragment(btnLesson4.getText().toString()));
        btnLesson5.setOnClickListener(new goToLessonStartFragment(btnLesson5.getText().toString()));
        btnLesson6.setOnClickListener(new goToLessonStartFragment(btnLesson6.getText().toString()));
        return view;
    }

    private class goToLessonStartFragment implements View.OnClickListener{
        private String lessonName;

        public goToLessonStartFragment(String lessonName){
            this.lessonName = lessonName;
        }

        @Override
        public void onClick(View v) {
            LessonStartFragment lessonStartFragment = new LessonStartFragment();

            FragmentTransaction transaction = getFragmentManager().beginTransaction();
            transaction.replace(R.id.fragment_container, lessonStartFragment);
            transaction.addToBackStack(null);
            transaction.commit();
        }
    }
}

I tried

LessonStartFragment lessonStartFragment = new LessonStartFragment();
TextView tv =  lessonStartFragment.getView().findViewById(v.getId());
tv.setText(lessonName);

But it returns

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference

I suppose that the id I get from v.getId() doesn't match the actual id in fragments's view components.

Every button (btnLesson1,btnLesson2,btnLesson3...so on..) has a title which is set on button's text. I am trying to set its text to the fragment's(LessonStartFragment) Textview.

How can I go about it?

I'd appreciate any help.

Thanks.

As the `NullPointerException` says it's already `lessonStartFragment.getView()` which returns `null` and not later in the parameter of `findViewById()`. — Michael Troger, Mar 29 '18 at 11:45
lessonStartFragment is initiated. OncreateView() will not be invoked and the view is null — Jyoti JK, Mar 29 '18 at 11:47

score 0 · Answer 1 · answered Mar 29 '18 at 12:18

0

Try to typecast Buttons like this:-

 btnLesson1 = (Button)view.findViewById(R.id.multiplication_lesson1);
 btnLesson2 = (Button)view.findViewById(R.id.multiplication_lesson2);
 btnLesson3 = (Button) view.findViewById(R.id.multiplication_lesson3);
 btnLesson4 = (Button) view.findViewById(R.id.multiplication_lesson4);
 btnLesson5 = (Button)view.findViewById(R.id.multiplication_lesson5);
 btnLesson6 = (Button)view.findViewById(R.id.multiplication_lesson6);

answered Mar 29 '18 at 12:18

Ankita

1,129
1
8
15

Thanks for trying. I appreciate it but the problem isn't with casting the view elements. It's with a null view returned by `getView()` I was able to set the TextView of another Fragment's view by using Bundles from this question https://stackoverflow.com/questions/12739909/send-data-from-activity-to-fragment-in-android – heisenberg Mar 29 '18 at 12:45

Getting view id of Button to change properties of fragment view component

1 Answers1