How to randomize questions without repetition from SQLite?

Question

I'm developing a simple quiz in my android studio. I'm using a database but I would like to randomize the questions every time the user clicks on the quiz button. I have created 5 sample questions so far.

Answer 1

I suggest doing:

Option1: If you don't want duplicate Questions

1. Use collections, since Sets doesn't allow duplicates and lists can be shuffled

2. Adapt (if not already) your class Question, so you can used in the Set and so not allowing duplicates...(by this override equals AND hashcode)

3. populate the Collection, shuffle it, get a random element of it

---

Option2: If you only want one of the questions at random

this is quite the same,

1. instead of using a set use a list...
2. omit step 2 since duplicated questions are no a big deal...
3. but still populate the Collection, shuffle it, get a random element of it

and there you are :)

Answer 2

Use Collections.shuffle on your List<Question>, then use an Iterator<Question> to pick out the questions as you click a button.

Assuming you implemented both equals and hashcode for your Question class, then a LinkedHashSet will remove the duplicates, so repetition won't happen.

Here is an Activity based on your class that should show these concepts.

public class QuizActivityMarketing extends Activity {

    private Iterator<Question> questionIterator;
    private TextView txtQuestion;
    private RadioButton rda, rdb, rdc, rdd;
    private Button butNext;

    private Question currentQ;
    private int score = 0;

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

        // Define your views
        txtQuestion = (TextView) findViewById(R.id.textView1);
        rda = (RadioButton) findViewById(R.id.radio0);
        rdb = (RadioButton) findViewById(R.id.radio1);
        rdc = (RadioButton) findViewById(R.id.radio2);
        rdd = (RadioButton) findViewById(R.id.radio3);
        butNext = (Button) findViewById(R.id.button1);

        // Get and randomize the questions
        DbHelperMarketing db = new DbHelperMarketing(this);
        final List<Question> questions = db.getAllQuestions();
        Collections.shuffle(questions);
        questionIterator = new LinkedHashSet<Question>(questions).iterator();

        // Setup the first question
        if (questionIterator.hasNext()) {
            currentQ = questionIterator.next();
            setQuestionView(currentQ);
        }

        // Hook up the button-clicking
        butNext.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                // Check the correct answer
                RadioGroup grp = (RadioGroup) findViewById(R.id.radioGroup1);
                RadioButton answer = (RadioButton) findViewById(grp.getCheckedRadioButtonId());
                Log.d("yourans", currentQ.getANSWER() + " " + answer.getText());
                if (currentQ.getANSWER().equals(answer.getText())) {
                    score++;
                    Log.d("score", "Your score" + score);
                }

                // Load the next question, if there are any
                if (questionIterator.hasNext()) {
                    currentQ = questionIterator.next();
                    setQuestionView(currentQ);
                } else { // Done asking questions
                    setQuestionView(null);

                    Intent intent = new Intent(QuizActivityMarketing.this, ResultActivity.class);
                    Bundle b = new Bundle();
                    b.putInt("score", score); //Your score
                    intent.putExtras(b); //Put your score to your next Intent
                    startActivity(intent);
                    finish();
                }
            }
        });
    }

    private void setQuestionView(Question currentQuestion) {
        if (currentQuestion != null) {
            txtQuestion.setText(currentQuestion.getQUESTION());
            rda.setText(currentQuestion.getOPTA());
            rdb.setText(currentQuestion.getOPTB());
            rdc.setText(currentQuestion.getOPTC());
            rdd.setText(currentQuestion.getOPTD());
        } else {
            txtQuestion.setText("");
            rda.setText("");
            rdb.setText("");
            rdc.setText("");
            rdd.setText("");
        }
    }

}