Non-repeating randomly generated questions - android-studio

Question

I'm trying to generate random questions into a quiz. Currently everything is fine but the questions are repeating, how would you keep them from repeating? I've read several articles but I just don't quite understand how to implement the code.
public class CplusQuiz extends AppCompatActivity {
Button answer1, answer2, answer3, answer4;
TextView score, question;
private Questions mQuestions = new Questions();
private String mAnswer;
private int mScore = 0;
private int mQuestionLength = mQuestions.mQuestions.length;
Random r;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_cplus_quiz);
r = new Random();
answer1 = (Button) findViewById(R.id.answer1);
answer2 = (Button) findViewById(R.id.answer2);
answer3 = (Button) findViewById(R.id.answer3);
answer4 = (Button) findViewById(R.id.answer4);
score = (TextView) findViewById(R.id.score);
question = (TextView) findViewById(R.id.question);
score.setText("Nerd Level: " + mScore);
updateQuestion(r.nextInt(mQuestionLength));
answer1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(answer1.getText() == mAnswer) {
mScore++;
score.setText("Score: "+ mScore);
updateQuestion(r.nextInt(mQuestionLength));
}
else {
gameOver();
}
}
});
answer2.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(answer2.getText() == mAnswer) {
mScore++;
score.setText("Score: "+ mScore);
updateQuestion(r.nextInt(mQuestionLength));
}
else {
gameOver();
}
}
});
answer3.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(answer3.getText() == mAnswer) {
mScore++;
score.setText("Score: "+ mScore);
updateQuestion(r.nextInt(mQuestionLength));
}
else {
gameOver();
}
}
});
answer4.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(answer4.getText() == mAnswer) {
mScore++;
score.setText("Score: "+ mScore);
updateQuestion(r.nextInt(mQuestionLength));
}
else {
gameOver();
}
}
});
}
private void updateQuestion(int num) {
question.setText(mQuestions.getQuestion(num));
answer1.setText(mQuestions.getChoice1(num));
answer2.setText(mQuestions.getChoice2(num));
answer3.setText(mQuestions.getChoice3(num));
answer4.setText(mQuestions.getChoice4(num));
mAnswer = mQuestions.getCorrectAnswer(num);
}
private void gameOver() {
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(CplusQuiz.this);
alertDialogBuilder
.setMessage("Epic Fail... Your nerd level is " + mScore + " ")
.setCancelable(false)
.setPositiveButton("Start Over",
new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int i) {
startActivity(new Intent(getApplicationContext(), CplusQuiz.class));
finish();
}
})
.setNegativeButton("EXIT TO MAIN",
new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int i) {
startActivity(new Intent(getApplicationContext(), MainActivity.class));
finish();
}
});
AlertDialog alertDialog = alertDialogBuilder.create();
alertDialog.show();
}
}
Questions.java file
package com.example.max.quiz;
/**
* Created by max on 4/24/2017.
*/
public class Questions {
public String mQuestions[] = {
"WHO IS THE FASTEST OF THESE VIDEO GAME CHARACTERS?",
"IN THE GAME HALO, WHAT IS THE NAME OF MASTER CHIEF'S AI SIDEKICK?",
"WHICH BAD GUY WAS INTRODUCED IN SUPER MARIO BROTHERS 2?",
"WHAT VIDEO GAME CONSOLE HAS THE HIGHEST NUMBER OF VIDEO GAME CONSOLE SALES OF ALL TIME?",
"WHICH OF THESE DO YOU NOT DO IN WE LOVE KATAMARI, THE SEQUEL TO KATAMARI DAMACY?",
"WHICH OF THESE BANDS IS NOT FEATURED IN GUITAR HERO III: LEGENDS OF ROCK?",
"HOW MANY UNLOCKABLE CHARACTERS CAN BE FOUND IN SUPER SMASH BROTHERS?",
"WHAT WAS NINTENDOS FIRST TRY AT AN ARCADE GAME?",
"WHICH DOES NOT HAVE WIFI?",
"WHAT VIDEO GAME CONSOLE HAS THE HIGHEST NUMBER OF VIDEO GAME CONSOLE SALES OF ALL TIME?",
};
private String mChoices[][] = {
{"Mario", "Sonic", "Donkey Kong", "The Paperboy"},
{"Cortana", "Arbiter", "343 Guilty Spark", "HAL"},
{"Koopa troopa", "Lakitu", "Shy Guy", "Goomba"},
{"Xbox 360", "Nintendo 64", "Wii", "PlayStation 2"},
{"roll around under water", "roll around while on fire", "roll around on the moon", "roll around a sumo wrestler"},
{"Metallica", "Weezer", "Iron Maiden", "Lynyrd Skynyrd"},
{"1", "2", "3", "4"},
{"Super Mario Brothers", "Donkey Kong Jr.", "Donkey Kong", "Final Fantasy"},
{"Mario Kart DS", "Diddy Kong Racing DS", "Tony Hawk's American Sk8land", "Super Mario 64 DS"},
{"Xbox 360", "Nintendo 64", "Wii", "PlayStation 2"},
};
private String mCorrectAnswers[] = {"Sonic", "Cortana", "Shy Guy", "PlayStation 2","roll around on the moon", "Iron Maiden", "4", "Donkey Kong", "Super Mario 64 DS", "PlayStation 2" };
public String getQuestion(int a) {
String question = mQuestions[a];
return question;
}
public String getChoice1(int a) {
String choice = mChoices[a][0];
return choice;
}
public String getChoice2(int a) {
String choice = mChoices[a][1];
return choice;
}
public String getChoice3(int a) {
String choice = mChoices[a][2];
return choice;
}
public String getChoice4(int a) {
String choice = mChoices[a][3];
return choice;
}
public String getCorrectAnswer (int a) {
String answer = mCorrectAnswers [a];
return answer;
}
}

Answer 1

Here's a solution in JavaScript - you can follow the logic and the hopefully apply the concepts to your Java project. There's a running demo in this Plunkr https://plnkr.co/edit/KcHh63ou25LZDaZ79iwI?p=preview
Basically what we're doing is creating an initial array of all the possible questions, and an empty array of questions we're going to include on the quiz. We decide how many questions to include, in this example 5, and then loop that number of times.
On each iteration, we get the current length of the array holding all the possible questions, and pick a random number between 0 and the number of questions left in the array, then we push the question at that index value onto our array of quiz questions, and slice that question out of our array of possible questions so it's not there to get picked a second time.
Then we iterate again, now the source question array is one shorter, we get it's new length, pick a new random number and grab that question, add it to our quiz array, slice it out of our source questions array.
Lather, rinse, repeat.
questionsSource = [{
"question": "What is your favourite colour?",
"answer": "blue",
}, {
"question": "What is the average airspeed of a coconut laden swallow?",
"answer": "African or European Swallow?",
}, {
"question": "Question 3?",
"answer": "Answer 3",
}, {
"question": "Question 4?",
"answer": "Answer 4",
}, {
"question": "Question 5?",
"answer": "Answer 5",
}, {
"question": "Question 6?",
"answer": "Answer 6",
}, {
"question": "Question 7?",
"answer": "Answer 7",
}, {
"question": "Question 8?",
"answer": "Answer 8",
}]
questionsLeft = questionsSource;
questionsPicked = [];
questionsInQuiz = 5; // how many questions you want to look up
for (i = 0; i < questionsInQuiz; i++) {
questionsLeftInArray = this.questionsLeft.length;
randNumber = Math.floor(Math.random() * questionsLeftInArray);
// pick a random number between 0 and the number of questions left in the array.
this.questionsPicked.push(questionsLeft[randNumber]);
// add the randomly selected question to the questionsPicked array.
this.questionsLeft.splice(randNumber, 1);
// remove that question from the remaining questions so it can't be picked again.
}
console.log("QuestionsSource", questionsSource);
console.log("questionsPicked", questionsPicked);
output = JSON.stringify(questionsPicked, null, 4)
document.write(output);