java.lang.NullPointerException in a fragment

Question

I am creating a custom listView on a fragment ..Attendance is a activity with swipable tabs i want custom list to appear on fragment_attendance_mark

this code was working fine in an activity ... but there is some issue when i tried to do the same on a swipable fragment ...

04-21 19:21:45.859: W/dalvikvm(18052): threadid=1: thread exiting with uncaught exception (group=0x2b542210)
04-21 19:21:45.879: E/AndroidRuntime(18052): FATAL EXCEPTION: main
04-21 19:21:45.879: E/AndroidRuntime(18052): java.lang.NullPointerException
04-21 19:21:45.879: E/AndroidRuntime(18052):    at com.example.markitberry.AttendanceMarkFragment.displayListView(AttendanceMarkFragment.java:66)
04-21 19:21:45.879: E/AndroidRuntime(18052):    at com.example.markitberry.AttendanceMarkFragment.onCreateView(AttendanceMarkFragment.java:35)
04-21 19:21:45.879: E/AndroidRuntime(18052):    at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500)
04-21 19:21:45.879: E/AndroidRuntime(18052):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
04-21 19:21:45.879: E/AndroidRuntime(18052):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
04-21 19:21:45.879: E/AndroidRuntime(18052):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
04-21 19:21:45.879: E/AndroidRuntime(18052):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)

Fragment_attandance_mark.java

public class AttendanceMarkFragment extends Fragment {

    MyCustomAdapter dataAdapter = null;
    ListView listView ;
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_attendance_mark, container, false);
        listView = (ListView) rootView.findViewById(R.id.listView1);

        //View rootView = inflater.inflate(R.layout.fragment_attendance_mark, container, false);

     // Generate list View from ArrayList
        displayListView();
            checkButtonClick(rootView);
        return rootView;
    }

    private void displayListView() {

        // Array list of countries
        ArrayList<AttendanceMarkListRow> stateList = new ArrayList<AttendanceMarkListRow>();

        AttendanceMarkListRow _AttendanceMarkListRow = new AttendanceMarkListRow("Ravi", "Male", "7 Aug",4,false,2);
        stateList.add(_AttendanceMarkListRow);
        _AttendanceMarkListRow = new AttendanceMarkListRow("Ravi", "Male", "7 Aug",4,false,2);
        stateList.add(_AttendanceMarkListRow);
        _AttendanceMarkListRow = new AttendanceMarkListRow("Div", "Male", "4 Aug",2,false,2);
        stateList.add(_AttendanceMarkListRow);
        _AttendanceMarkListRow = new AttendanceMarkListRow("Hari", "Male", "1 Aug",1,false,2);
        stateList.add(_AttendanceMarkListRow);
        _AttendanceMarkListRow = new AttendanceMarkListRow("Suu", "Male", "3 Aug",5,false,2);
        stateList.add(_AttendanceMarkListRow);
        _AttendanceMarkListRow = new AttendanceMarkListRow("Dhaka", "Male", "5 Aug",0,false,2);
        stateList.add(_AttendanceMarkListRow);
        _AttendanceMarkListRow = new AttendanceMarkListRow("Chu", "Male", "8 Aug",4,false,2);
        stateList.add(_AttendanceMarkListRow);
        _AttendanceMarkListRow = new AttendanceMarkListRow("Nikita", "Female", "9 Aug",4,false,2);
        stateList.add(_AttendanceMarkListRow);
        _AttendanceMarkListRow = new AttendanceMarkListRow("Ravi Ranjan", "Male", "0 Aug",4,false,2);
        stateList.add(_AttendanceMarkListRow);

        // create an ArrayAdaptar from the String Array
        dataAdapter = new MyCustomAdapter(this.getActivity(), R.layout.list_row, stateList);
        ListView listView = (ListView) getView().findViewById(R.id.listView1);
        // Assign adapter to ListView
        listView.setAdapter(dataAdapter);

        listView.setOnItemClickListener(new OnItemClickListener() {

            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {
                // When clicked, show a toast with the TextView text
                AttendanceMarkListRow state = (AttendanceMarkListRow) parent.getItemAtPosition(position);
                Toast.makeText(getActivity().getApplicationContext(),
                        "Clicked on : " + state.getName(), Toast.LENGTH_LONG)
                        .show();
            }
        });
    }

    private class MyCustomAdapter extends ArrayAdapter<AttendanceMarkListRow> {

        private ArrayList<AttendanceMarkListRow> stateList;

        public MyCustomAdapter(Context context, int textViewResourceId,

        ArrayList<AttendanceMarkListRow> stateList) {
            super(context, textViewResourceId, stateList);
            this.stateList = new ArrayList<AttendanceMarkListRow>();
            this.stateList.addAll(stateList);
        }

        private class ViewHolder {
            TextView gender;
            TextView lastseen;
            CheckBox name;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            ViewHolder holder = null;

            Log.v("ConvertView", String.valueOf(position));

            if (convertView == null) {

                LayoutInflater vi = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);

                convertView = vi.inflate(R.layout.list_row, null);

                holder = new ViewHolder();
                holder.gender = (TextView) convertView.findViewById(R.id.gender);
                holder.lastseen = (TextView) convertView.findViewById(R.id.lastSeen);
                holder.name = (CheckBox) convertView
                        .findViewById(R.id.checkBox1);

                convertView.setTag(holder);

                holder.name.setOnClickListener(new View.OnClickListener() {
                    public void onClick(View v) {
                        CheckBox cb = (CheckBox) v;
                        AttendanceMarkListRow _state = (AttendanceMarkListRow) cb.getTag();


                        Toast.makeText(
                                getActivity().getApplicationContext(),
                                "Checkbox: " + cb.getText() + " -> "
                                        + cb.isChecked(), Toast.LENGTH_LONG)
                                .show();

                        _state.setSelected(cb.isChecked());
                    }
                });

            } else {
                holder = (ViewHolder) convertView.getTag();
            }

            AttendanceMarkListRow state = stateList.get(position);

            holder.gender.setText(state.getGender());
            holder.lastseen.setText(state.getLastSeen());
            holder.name.setText(state.getName());
            holder.name.setChecked(state.isSelected());
            holder.name.setTag(state);

            return convertView;
        }

    }

    private void checkButtonClick(View view) {

        Button myButton = (Button) view.findViewById(R.id.butBdaySelectNext);

        myButton.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                StringBuffer responseText = new StringBuffer();
                responseText.append("Selected Countries are...\n");

                ArrayList<AttendanceMarkListRow> stateList = dataAdapter.stateList;

                for (int i = 0; i < stateList.size(); i++) {
                    AttendanceMarkListRow state = stateList.get(i);

                    if (state.isSelected()) {
                        responseText.append("\n" + state.getName());
                    }
                }

                Toast.makeText(getActivity().getApplicationContext(), responseText,
                        Toast.LENGTH_LONG).show();
            }
        });
    }  

}

Answer 1

You're calling displayListView() from onCreateView() and you're calling getView() there. Now, onCreateView() hasn't yet returned the view so getView() returns null. Instead, pass the view as a parameter from onCreateView() to displayListView() .

Answer 2

The below probably causes NullPointerException .

ListView listView = (ListView) getView().findViewById(R.id.listView1);

So change to

 ListView listView ;
 public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.fragment_attendance_mark, container, false);
    listView = (ListView) rootView.findViewById(R.id.listView1);
 // Generate list View from ArrayList
        displayListView();
        checkButtonClick();
    return rootView;
}

Or as laalto suggested

displayListView(rootView);

Then

private void displayListView(View View) {

   ListView listView = (ListView) view.findViewById(R.id.listView1);
}

or

In onActivityCreated

 ListView listView = (ListView) getView().findViewById(R.id.listView1);

Edit:

  checkButtonClick(rootView);

Then

   private void checkButtonClick(View view) {

    Button myButton = (Button) view.findViewById(R.id.butBdaySelectNext);