Android :: How do I randomize my quiz questions?

Question

I have a quiz application what show few questions from the SQLite Db, it has 50 questions, but it must be show 5 questions in the game part and will be randomize these.

I tired many times for the solution, but nothing :/

In the source code qid is the Db. ID primery key which is based on show the questions and find the answer.

Here is the Activity:

package com.example.quiz;

import java.util.List;
import java.util.Random;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.database.DatabaseUtils;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;

public class QuizActivity extends Activity {
    private static final DbHelper remote = null;
    List <Question> quesList;
    int score = 0;

    Question currentQ;
    TextView txtQuestion;
    RadioButton rda, rdb, rdc, rdd;
    Button butNext;

    int qid;
    int qNumber = 0;


    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_quiz);
        DbHelper db = new DbHelper(this);

        quesList = db.getAllQuestions();
        currentQ = quesList.get(qid);

        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);

        setQuestionView();

        butNext.setOnClickListener(new View.OnClickListener() { 

            @Override
            public void onClick(View v) {
                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);
                }

                if(qNumber < 5){    

                    currentQ = quesList.get(qid);
                    setQuestionView();
                }

                else

                {
                    Intent intent = new Intent(QuizActivity.this, ResultActivity.class);
                    Bundle b = new Bundle();
                    b.putInt("score", score); //Pontunk
                    intent.putExtras(b); //Pont tovább vivése a következő kérdéshez
                    startActivity(intent);
                    finish();
                }
            }
        });
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.quiz, menu);
        return true;
    }
    private void setQuestionView()
    {
        txtQuestion.setText(currentQ.getQUESTION());
        rda.setText(currentQ.getOPTA());
        rdb.setText(currentQ.getOPTB());
        rdc.setText(currentQ.getOPTC());
        rdd.setText(currentQ.getOPTD());

        Random rand = new Random(); 
        for(int i=0; i<5;i++){
        int r1 = rand.nextInt(50) + 1;
        qid = r1;
        }
        qNumber++;
    }
}

When qNumber's value more than 5, it redirect to the ResultsActivity. I tested it, and its work, show the random questions, but sometimes the program crashed. Where I wrong it, and why dont work the randomization normally?

Thanks for the help, and sorry my english knowledge!

Answer 1

You can fetch the random questions by running this query:

db.rawQuery("SELECT * FROM YOUR_TABLE ORDER BY RANDOM() LIMIT 5", null);

Answer 2

The most important thing to do is to check the crash information: that will tell you where to look.

However, I think I can see the problem. Your random number generator returns a value between 0 and 49 and then adds 1, placing a value in variable qid in the range 1 to 50. But a List is zero-based, so when you access element 50 it crashes. (And question 0 will never be accessed).