How to use loop on Listview- returning same list item

Question

I'm trying to create a quiz app page with swipe function. Each page shows a question and 3 optional answers. For the answers I'm using listview. Contents of listview are not looping. Every time I swipe pages, the answer list keep showing row of option-1. Please anyone help.

public class FActivity extends FragmentActivity {
    public static TextView mTitleView;
    public static TextView mQuestionView;
    public static ListView answerView;
    private static String[]singleRow;
    private static ArrayAdapter<String> arrayAdapter;
    public static int index = 6;

    CollectionPagerAdapter mCollectionPagerAdapter;

    static ViewPager mViewPager;
    private static final String TAG = "QuizActivity";


    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_collection);
        mCollectionPagerAdapter = new CollectionPagerAdapter(getSupportFragmentManager());


        populateListView();

        // Set up the ViewPager, attaching the arrayAdapter.
        mViewPager = (ViewPager)findViewById(R.id.pager);
        mViewPager.setAdapter(mCollectionPagerAdapter);

    }

      private String[] populateListView() {

    int row = 0;
    if (row < QuestionAndAnswer.Answer.getmAnswer().length) {
        singleRow = QuestionAndAnswer.Answer.getmAnswer()[row++];
        Log.d(TAG, Arrays.toString(QuestionAndAnswer.Answer.getmAnswer()[row]));
        arrayAdapter = new ArrayAdapter<>
                (this, //context
                R.layout.activity_f, //textView set up in xml
                singleRow    //name of array
                );
    }return singleRow;
}

    public static class CollectionPagerAdapter extends FragmentStatePagerAdapter implements com.example.michikoote.testa.CollectionPagerAdapter {

        public CollectionPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int m) {
            ObjectFragment fragment2 = new ObjectFragment();
            Bundle args = new Bundle();
            args.putInt(ObjectFragment.ARG_OBJECT, m + 1); //object is just an integer
            fragment2.setArguments(args);
            return fragment2;
        }

        @Override
        public int getCount() {
            // determine how many pages to show
            return index;
        }
    }


    public static class ObjectFragment extends Fragment {

        public static final String ARG_OBJECT = "";

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_collection_object, container, false);
            Bundle args = getArguments();


            mTitleView = (TextView) rootView.findViewById(R.id.page_number);
            mTitleView.setText((Integer.toString(args.getInt(ARG_OBJECT))) + "/" + index);

            mQuestionView = (TextView) rootView.findViewById(R.id.tv_question);
            mQuestionView.setText(Question.GetSingleQuestion());

            return rootView;
        }

    }

}

QuestionAndAnswer.java -class file

       public class QuestionAndAnswer {
        private static final String TAG = "MyActivity";

        public static int maxPagenumber;

        public static class Question {
            public static int q = 0;


            public static String GetSingleQuestion() {
                String[] mQuestion = {
                        "question1",
                        "question2",
                        "question3",
                        "question4",
                        "question5"
                };

                if (q > mQuestion.length-1) {
                }
                return mQuestion[q++];
            }

        }

        public static class Answer {

            public static String[][] getmAnswer() {
                return mAnswer;
            }

            private static String[][] mAnswer = {
                    {"option1-1", "option1-2", "option1-3"},
                    {"option2-1", "option2-2"},
                    {"option3-1", "option3-2", "option3-3"},
                    {"option4-1", "option4-2", "option4-4"},
                    {"option5-1", "option5-2"},
            };
        }
    }

activity_f.xml -layout

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
</TextView>

Kevin Crain · Accepted Answer · 2015-02-01 10:53:51Z

1

Change this below:

private void populateListView() {

    for (int row = 0;row < QuestionAndAnswer.Answer.getmAnswer().length; row++) {
        singleRow = Answer.getmAnswer()[row];
        //set Answer
        answerView = (ListView)this.findViewById(R.id.li_answers);
        answerView.setAdapter(arrayAdapter);
        Log.d(TAG, Arrays.toString(Answer.getmAnswer()[row]));
    }
    arrayAdapter = new ArrayAdapter<String>
            (this, //context
                    R.layout.activity_f, //textView set up in xml
                    singleRow    //name of array
            );


}

To this:

private void populateListView() {

    arrayAdapter = new ArrayAdapter<String>
                (this, //context
                        R.layout.activity_f, //textView set up in xml
                        singleRow    //name of array
                );

    for (int row = 0;row < QuestionAndAnswer.Answer.getmAnswer().length; row++) {
        singleRow = Answer.getmAnswer()[row];
        //set Answer
        answerView = (ListView)this.findViewById(R.id.li_answers);
        answerView.setAdapter(arrayAdapter);
        Log.d(TAG, Arrays.toString(Answer.getmAnswer()[row]));
    }  
}

answered Feb 1, 2015 at 10:53

Kevin Crain

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2 Comments

Ellen Spertus Over a year ago

Could you explain why the change should be made?

Kevin Crain Over a year ago

The change should be made because the arrayAdapter is null before you use setAdapter on the listview and thats why you get NullPointerException.

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