Android arrayList检索数据

Question

我有两节课：

question model.Java

   package com.invertemotech.quizapp;



 public class QuestionModel {

public QuestionModel(String questionString, String answer ,String optA, 
 String optB, String optC , String optD) {
    QuestionString = questionString;
    Answer = answer;
    OptA = optA;
    OptB = optB;
    OptC = optC;
    OptD= optD;

}

public String getQuestionString() {

        return QuestionString;
}

public void setQuestionString (String questionString) {
        QuestionString = questionString;
}

public void setOptA(String optA) {
    OptA = optA;
}

public String getOptA() {

    return OptA;
}


public void setOptB(String optB) {
    OptB = optB;
}

public String getOptB() {
    return OptB;
}

public String getOptC() {
    return OptC;
}

public void setOptC(String optC) {
    OptC = optC;
}

public String getOptD() {
    return OptD;
}

public void setOptD(String optD) {
    OptD = optD;
}


public String getAnswer() {
    return Answer;
}

public void setAnswer(String answer)
{
    Answer = answer;
}

private String QuestionString;
private String OptA;
private String OptB;
private String OptC;
private String OptD;
private String Answer;


}

main activity.Java

   package com.invertemotech.quizapp;

 import android.support.v7.app.AppCompat Activity;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.KeyEvent;
  import android.view.View;
  import android.widget.Button;
  import android.widget.EditText;
  import android.widget.ProgressBar;
  import android.widget.RadioButton;
  import android.widget.RadioGroup;
  import android.widget.TextView;
  import android.widget.Toast;

  import java.util.ArrayList;
   import java.util.Collections;
   import java.util.Random;

  import cn.pedant.SweetAlert.SweetAlertDialog;

   public class MainActivity extends AppCompatActivity {

   ArrayList<QuestionModel> questionModelArraylist;

    TextView questionLabel, questionCountLabel, scoreLabel ;
   //    EditText answerEdt;
   //    TextView txtQuestion;
   RadioButton option1, option2 , option3 ;
   Button submitButton;
   ProgressBar progressBar;
   QuestionModel currentQuestion;

   int currentPosition = 0;
   int numberOfCorrectAnswer = 0;


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


    questionCountLabel = findViewById(R.id.noQuestion);
    questionLabel = findViewById(R.id.question);
    scoreLabel = findViewById(R.id.score);
    option1 = findViewById(R.id.option1);
    option2 = findViewById(R.id.option2);
    option3 = findViewById(R.id.option3);
   //        option4 = findViewById(R.id.option4);
    submitButton = findViewById(R.id.submit);
    progressBar = findViewById(R.id.progress);

    questionModelArraylist = new ArrayList<>();
    questionModelArraylist.add(new QuestionModel("Which company is the 
    largest manufacturer of network equipment ?", "IBM", "A: IBM",  "B: 
    CICSO", "C: 
      DELL" , "D: HP"));
    questionModelArraylist.add(new QuestionModel("Which of the following is 
    NOT an operating system ?", "Bios", "A: BIOS", "B: LINUX", "C: WINDOWS" 
    , "D: MAC"));
    questionModelArraylist.add(new QuestionModel("Who is the first cricketer 
    to score an international double century in 50-over match ?", "Sachin 
     Tendulkar", "A: Sachin Tendulkar", "B: Brian Lara", "C: Rohit Sharma" , 
    "D: Rahul Dravid"));
    questionModelArraylist.add(new QuestionModel("Who is the founder of 
    Apple Inc. ?", "Steve", "A: Bill Gates", "B: Steve Jobs", "C: Suresh" , 
    "D: Mark"));

    questionModelArraylist.add(new QuestionModel("Which is the biggest 
    largest city in the world ?", "Reno", "A: Shanghai", "B: Vienna", "C: 
    Reno" , "D: Hong Kong"));


    Collections.shuffle(questionModelArraylist , new Random());
    currentQuestion = questionModelArraylist.get(currentPosition);

    setData();

  //        setUpQuestion();

    submitButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            checkAnswer();
        }
    });



}
public void checkAnswer(){
    RadioGroup grp = findViewById(R.id.options);
    RadioButton answer = findViewById(grp.getCheckedRadioButtonId());
    String newAnswer = String.valueOf(answer.getText());

    if(newAnswer.equalsIgnoreCase(questionModelArraylist
    .get(currentPosition).getAnswer())){
            numberOfCorrectAnswer ++;
            Log.d("Score", "Your score: "+            newAnswer);



        new SweetAlertDialog(MainActivity.this, 
   SweetAlertDialog.SUCCESS_TYPE)
                .setTitleText("Good job! Keep Going")
                .setContentText("Right Answer")
                .setConfirmClickListener(new 
   SweetAlertDialog.OnSweetClickListener() {
                    @Override
                    public void onClick(SweetAlertDialog sweetAlertDialog) {
                        currentPosition ++;

                        setData();
   //                            answerEdt.setText("");
                        sweetAlertDialog.dismiss();
                    }
                })
                .show();


    }else {

        new SweetAlertDialog(MainActivity.this, 
    SweetAlertDialog.WARNING_TYPE)
                .setTitleText("Wrong Answer")
                .setContentText("The right answer is : 
   "+questionModelArraylist.get(currentPosition).getAnswer())
                .setConfirmText("OK")
                .setConfirmClickListener(new 
    SweetAlertDialog.OnSweetClickListener() {
                    @Override
                    public void onClick(SweetAlertDialog sDialog) {
                        sDialog.dismiss();

                        currentPosition ++;

                        setData();
   //                            answerEdt.setText("");
                    }
                })
                .show();
    }





    int x = ((currentPosition+1) * 100) / questionModelArraylist.size();

    progressBar.setProgress(x);



}


public void setData(){


    if(questionModelArraylist.size()>currentPosition) {
   questionLabel.setText(questionModelArraylist
   .get(currentPosition).getQuestionString());

  option1.setText(questionModelArraylist.get(currentPosition).getOptA());

  option2.setText(questionModelArraylist.get(currentPosition).getOptB());

  option3.setText(questionModelArraylist.get(currentPosition).getOptC());
  //            
   option4.setText(questionModelArraylist.get(currentPosition).getOptD());


        scoreLabel.setText("Score :" + numberOfCorrectAnswer + "/" + 
  questionModelArraylist.size());
        questionCountLabel.setText("Question No : " + (currentPosition + 
  1));


    }else{


        new SweetAlertDialog(MainActivity.this, 
   SweetAlertDialog.SUCCESS_TYPE)
                .setTitleText("You have successfully completed the quiz")
                .setContentText("Your score is : "+ numberOfCorrectAnswer + 
 "/" + questionModelArraylist.size())
                .setConfirmText("Restart")
                .setConfirmClickListener(new SweetAlertDialog.OnSweetClickListener() {
                    @Override
                    public void onClick(SweetAlertDialog sDialog) {

                        sDialog.dismissWithAnimation();
                        currentPosition = 0;
                        numberOfCorrectAnswer = 0;
                        progressBar.setProgress(0);
                        setData();
                    }
                })
                .setCancelText("Close")
                .setCancelClickListener(new 
     SweetAlertDialog.OnSweetClickListener() {
                    @Override
                    public void onClick(SweetAlertDialog sDialog) {

                        sDialog.dismissWithAnimation();
                        finish();
                    }
                })
                .show();

    }

 }

}

我如何在ArrayList中限制。就像我在其中放入300个问题一样，我必须随机使用所有10个问题。每当应用程序打开时，所有问题都应该是随机的，但只有300个问题。它是android中的初级程序。

Answer 1

如果源列表具有唯一项，则可以使用以下逻辑：

public static List<String> getRandomList(List<String> list, int n) {
    List<String> copy = new LinkedList<String>(list);
    Collections.shuffle(copy);
    return copy.subList(0, n);
}