java中如何获取ArrayList中的下一个项目

Question

我遵循了一个关于使用 java android studio 编写测验应用程序的 YouTube 教程，在教程中，您将问题放入数组列表中，然后从中随机得到问题，这可能会导致多次得到相同问题的问题。我该如何解决这个问题？我想过不使用随机，而是使用函数来获取列表中的下一个项目，但它对我不起作用。是的，这是我的代码

package com.example.quiz20;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;

import com.google.android.material.bottomsheet.BottomSheetDialog;

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

public class MainActivity extends AppCompatActivity {
    private TextView questionTV,questionNumberTV;
    private Button option1Btn,option2Btn,option3Btn,option4Btn;
    private ArrayList<QuizModel> quizModelArrayList;
    Random random;
    int currentScore = 0 , questionAttempted = 0, currentPos;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        questionTV= findViewById(R.id.idTVQuestion);
        questionNumberTV=findViewById(R.id.idTVQuestionAttempted);
        option1Btn=findViewById(R.id.idBtnOption1);
        option2Btn=findViewById(R.id.idBtnOption2);
        option3Btn=findViewById(R.id.idBtnOption3);
        option4Btn=findViewById(R.id.idBtnOption4);
        quizModelArrayList = new ArrayList<>();
        random = new Random();
        getQuizQuestion(quizModelArrayList);
        currentPos = random.nextInt(quizModelArrayList.size());
        setDataToViews(currentPos);
        option1Btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(quizModelArrayList.get(currentPos).getAnswer().trim().toLowerCase().equals(option1Btn.getText().toString().trim().toLowerCase())){
                    currentScore++;
                }
                questionAttempted++;
                currentPos = random.nextInt(quizModelArrayList.size());
                setDataToViews(currentPos);

            }
        });

        option2Btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(quizModelArrayList.get(currentPos).getAnswer().trim().toLowerCase().equals(option2Btn.getText().toString().trim().toLowerCase())){
                    currentScore++;
                }
                questionAttempted++;
                currentPos = random.nextInt(quizModelArrayList.size());
                setDataToViews(currentPos);
            }
        });

        option3Btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(quizModelArrayList.get(currentPos).getAnswer().trim().toLowerCase().equals(option3Btn.getText().toString().trim().toLowerCase())){
                    currentScore++;
                }
                questionAttempted++;
                currentPos = random.nextInt(quizModelArrayList.size());
                setDataToViews(currentPos);
            }
        });

        option4Btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(quizModelArrayList.get(currentPos).getAnswer().trim().toLowerCase().equals(option4Btn.getText().toString().trim().toLowerCase())){
                    currentScore++;
                }
                questionAttempted++;
                currentPos = random.nextInt(quizModelArrayList.size());
                setDataToViews(currentPos);
            }
        });

    }

    private void showBottomSheet(){
        BottomSheetDialog bottomSheetDialog = new BottomSheetDialog(MainActivity.this);
        View bottomSheetView = LayoutInflater.from(getApplicationContext()).inflate(R.layout.score_bottom_sheet,(LinearLayout)findViewById(R.id.idLLScore));
        TextView scoreTV = bottomSheetView.findViewById(R.id.idTVScore);
        Button restartQuizBtn = bottomSheetView.findViewById(R.id.idBtnRestart);
        scoreTV.setText("you score is \n"+currentScore + "/4");
        restartQuizBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                currentPos = random.nextInt(quizModelArrayList.size());
                setDataToViews(currentPos);
                questionAttempted = 0;
                currentScore = 0;
                bottomSheetDialog.dismiss();
            }
        });
        bottomSheetDialog.setCancelable(false);
        bottomSheetDialog.setContentView(bottomSheetView);
        bottomSheetDialog.show();
    }

    private void setDataToViews(int currentPos){
        questionNumberTV.setText("Question Attempted : "+questionAttempted + "/4");
        if(questionAttempted == 4){
            showBottomSheet();
        }else {
            questionTV.setText(quizModelArrayList.get(currentPos).getQuestion());
            option1Btn.setText(quizModelArrayList.get(currentPos).getOption1());
            option2Btn.setText(quizModelArrayList.get(currentPos).getOption2());
            option3Btn.setText(quizModelArrayList.get(currentPos).getOption3());
            option4Btn.setText(quizModelArrayList.get(currentPos).getOption4());
        }


    }
    private void getQuizQuestion(ArrayList<QuizModel> quizModelArrayList) {
        quizModelArrayList.add(new QuizModel("in which year google released?","1998","2000","2004","1995","1998"));
        quizModelArrayList.add(new QuizModel("What does CPU stand for?","Core Processing Unit","Central Processing Unit","Command Processing Unit","Custom Processing Unit","Central Processing Unit"));
        quizModelArrayList.add(new QuizModel("what is the name of the first internet search engine?","Google","Yahoo","AOL","Archie","Archie"));
        quizModelArrayList.add(new QuizModel("Which Programming language is the most widely used?","JavaScript","JAVA","Python","PHP","JavaScript"));

    }
}

Answer 1

为了避免多次获得相同的选择，您可能需要在选择后将其从列表中删除。语法可能如下所示：

    Random rand = new Random();
    ArrayList <Type> list = new ArrayList<>();
    int selection = rand.nextInt(list.size() + 1);

    switch(selection)
    {
        case X:
            do the X stuff;
            list.remove(X);
            break;
    }

ArrayList 知道索引 X 位于什么位置，因此通过名称调用它会删除该条目。使用 ArrayList 的大小来创建随机数的界限也有助于保持其动态

注意这不是完整的代码

有关使用以下内容保留 ArrayList 内容的信息/示例list.clone()

https://www.tutorialspoint.com/clone-an-arraylist-in-java - 可以使用 java.util.ArrayList.clone() 方法克隆 ArrayList。此方法不带任何参数，但返回指定 ArrayList 实例的浅表副本。这意味着使用 ArrayList.clone() 方法创建的新 ArrayList 引用与原始 ArrayList 相同的元素，但不会重复这些元素。