在真实设备

Question

我正在开发测验应用程序，其中用户可以在特定时间解决测验，但是当我在模拟器上运行应用程序时，它运行时没有错误，但在真实设备上运行应用程序时，它会引发跟随错误。

错误： -

    java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2683)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2744)
    at android.app.ActivityThread.-wrap12(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1493)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:6195)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:874)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:764)
    Caused by: java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
    at java.util.ArrayList.get(ArrayList.java:411)
    at com.gaurav.javascripttutorial.subactivities.QuizMainActivity.onCreate(QuizMainActivity.java:52)

代码： -

public class QuizMainActivity extends AppCompatActivity {

    private ProgressBar countDownTimer;
    private TextView timer;
    public int counter;

    List<Question> quesList;
    int score=0;
    int qid=0;
    Question currentQ;
    TextView txtQuestion;
    RadioButton rda, rdb, rdc;
    Button butNext;

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

        /**
         * Quiz coding
         */

        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);
        butNext=(Button)findViewById(R.id.nextButton);
        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(qid<22){
                    currentQ=quesList.get(qid);
                    setQuestionView();
                }else{
                    Intent intent = new Intent(QuizMainActivity.this, QuizResultActivity.class);
                    Bundle b = new Bundle();
                    b.putInt("score", score); //Your score
                    intent.putExtras(b); //Put your score to your next Intent
                    startActivity(intent);
                    finish();
                }
            }
        });

        /**
         * Timer Coding
         */
        countDownTimer = (ProgressBar) findViewById(R.id.progressBar);
        timer = (TextView) findViewById(R.id.timer);

        new CountDownTimer(1200000,1000){

            @Override
            public void onTick(long millisUntilFinished) {
                int progress = (int) (millisUntilFinished/120000)+1;
                countDownTimer.setProgress(countDownTimer.getMax()-progress);
                if (counter == 1080){
                    Toast.makeText(QuizMainActivity.this, "Only 2 minutes remaining, Please review the answers.", Toast.LENGTH_SHORT).show();
                }
               counter++;
                Log.d("Counter number", ""+counter);
            }

            @Override
            public void onFinish() {
                Toast.makeText(QuizMainActivity.this, "Sorry! Time is over, Try again", Toast.LENGTH_LONG).show();
                finish();
            }
        }.start();
    }

    @Override
    public void onBackPressed() {
        super.onBackPressed();
        finish();
    }

    private void setQuestionView()
    {
        txtQuestion.setText(currentQ.getQUESTION());
        rda.setText(currentQ.getOPTA());
        rdb.setText(currentQ.getOPTB());
        rdc.setText(currentQ.getOPTC());
        qid++;
    }
}

当程序运行并且错误抛出时，光标表示代码的以下行： -

currentQ=quesList.get(qid);

Answer 1

请检查gelAllQuestions（）函数。首先如果函数没有返回空列表，则应该进行null检查。之后，您可以使用isEmpty（）函数检查列表是否为空。

请确保数据库中有可用的数据。

Answer 2

创建List后，必须使用它的构造函数实现它。所以在使用List之前添加这一行：

    quesList = new ArrayList<>();