如何从firebase firestore数据库中获得随机查询

Question

我正在制作一个问答应用程序，其中我有类别，当我选择一个类别时，问题开始来自firebase firestore数据库，在每个类别中，我在数据库中有10个问题，我希望所有问题都从firebase数据库加载，每次都以随机顺序出现，

但我的问题是，所有的问题都不是加载，有时加载5，有时加载7，这种随机顺序继续进行。

我对firebase数据库不太了解，下面是我尝试的代码

我的测验活动代码

public class QuizActivity extends AppCompatActivity {
ActivityQuizBinding binding;
ArrayList<Questions> qestions;
Questions question;
CountDownTimer timer;
FirebaseFirestore database;
int correctAnswer = 0;
int index = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

binding = ActivityQuizBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());
qestions = new ArrayList<>();
database = FirebaseFirestore.getInstance();
final   String cateGoryID = getIntent().getStringExtra("categoryID");
Random random = new Random();
final   int rand = random.nextInt(10);
database.collection("categories")
.document(cateGoryID)
.collection("questions")
.whereGreaterThanOrEqualTo("index",rand)
.orderBy("index")
.limit(5)
.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
@Override
public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
if (queryDocumentSnapshots.getDocuments().size()<5){
database.collection("categories")
.document(cateGoryID)
.collection("questions")
.whereLessThanOrEqualTo("index",rand)
.orderBy("index")
.limit(5)
.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
@Override
public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
for (DocumentSnapshot snapshot : queryDocumentSnapshots){
Questions questions = snapshot.toObject(Questions.class);
qestions.add(questions);
}
setNextQestions();
}
});

} else {
for (DocumentSnapshot snapshot : queryDocumentSnapshots){
Questions questions = snapshot.toObject(Questions.class);
qestions.add(questions);
}
setNextQestions();

}
}
});

resetTimer();
}
void resetTimer(){
timer = new CountDownTimer(30000,1000) {
@Override
public void onTick(long l) {
binding.timer.setText(String.valueOf(l/1000));
}
@Override
public void onFinish() {
}
};
}
public void CheckAnwer(TextView textView){
String selectAnswer = textView.getText().toString();
if(selectAnswer.equals(question.getAnswer())){
correctAnswer++ ;
textView.setBackground(getResources().getDrawable(R.drawable.option_right));
}
else{
showAnswer();
textView.setBackground(getResources().getDrawable(R.drawable.option_wrong));
}
}

@Override
public void onBackPressed() {
new AlertDialog.Builder(QuizActivity.this)
.setIcon(R.drawable.ic_baseline_person_24)
.setMessage("Are you sure want to Quit Game")
.setPositiveButton("yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
Intent in = new Intent(QuizActivity.this,MainActivity.class);
startActivity(in);
finish();
}
}).setNegativeButton("No", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
dialogInterface.dismiss();
}
}).create().show();
}

public void setNextQestions() {
if(timer != null){
timer.cancel();
}


timer.start();

if (index < qestions.size()) {
binding.qestioncounter.setText(String.format("%d/%d",(index+1),qestions.size()));
question = qestions.get(index);
binding.qestions.setText(question.getQestion());
binding.option1.setText(question.getOption1());
binding.option2.setText(question.getOption2());
binding.option3.setText(question.getOption3());
binding.option4.setText(question.getOption4());
}
}
void reset(){
binding.option1.setBackground(getResources().getDrawable(R.drawable.option_unselected));
binding.option2.setBackground(getResources().getDrawable(R.drawable.option_unselected));
binding.option3.setBackground(getResources().getDrawable(R.drawable.option_unselected));
binding.option4.setBackground(getResources().getDrawable(R.drawable.option_unselected));
}

void showAnswer(){
if (question.getAnswer().equals(binding.option1.getText().toString()))
binding.option1.setBackground(getResources().getDrawable(R.drawable.option_right));
else  if (question.getAnswer().equals(binding.option2.getText().toString()))
binding.option2.setBackground(getResources().getDrawable(R.drawable.option_right));
else  if (question.getAnswer().equals(binding.option3.getText().toString()))
binding.option3.setBackground(getResources().getDrawable(R.drawable.option_right));
else  if (question.getAnswer().equals(binding.option4.getText().toString()))
binding.option4.setBackground(getResources().getDrawable(R.drawable.option_right));
}
public void onClick(View view){
switch (view.getId()){
case R.id.option_1:
case R.id.option_2:
case R.id.option_3:
case R.id.option_4:
if(timer != null){
timer.cancel();
}
TextView selected = (TextView) view;
CheckAnwer(selected);
break;
case R.id.next_btn:
// reset();
if (index < qestions.size()){
reset();
index++;
setNextQestions();}
else {
Toast.makeText(this, "Quiz Finsished", Toast.LENGTH_SHORT).show();
Intent in = new Intent(QuizActivity.this,ResultActivity.class);
in.putExtra("correct_answer",correctAnswer);
in.putExtra("total",qestions.size());
startActivity(in);
}
break;



}
}

Answer 1

最简单的方法是在不使用随机的情况下加载所有问题，并在将所有问题添加到qestions数组列表后，对其进行洗牌。

for (DocumentSnapshot snapshot : queryDocumentSnapshots){
Questions questions = snapshot.toObject(Questions.class);
qestions.add(questions);
}
Collections.shuffle(questions);
setNextQestions();

做出这样的更改。

case R.id.next_btn:
setNextQestions();
break;

setNextQ估计方法

public void setNextQestions() {
if(timer != null){
timer.cancel();
}
timer.start();
if (index < qestions.size()) {
binding.qestioncounter.setText(String.format("%d/%d",(index+1),qestions.size()));
question = qestions.get(index);
binding.qestions.setText(question.getQestion());
binding.option1.setText(question.getOption1());
binding.option2.setText(question.getOption2());
binding.option3.setText(question.getOption3());
binding.option4.setText(question.getOption4());
index++;
}
else {
reset();
Toast.makeText(this, "Quiz Finsished", Toast.LENGTH_SHORT).show();
Intent in = new Intent(QuizActivity.this,ResultActivity.class);
in.putExtra("correct_answer",correctAnswer);
in.putExtra("total",qestions.size());
startActivity(in);
}
}