java - 请帮助 : java. lang.IndexOutOfBoundsException : Invalid index 0, 大小为 0

Question

我做了一个多项选择的问答游戏。我从数据库中获取问题和多项选择题的答案。从数据库中检索并检查正确答案。我使用的数据库是sqlite数据库。我的异常代码:

11-03 17:43:11.108: E/AndroidRuntime(640): FATAL EXCEPTION: main
11-03 17:43:11.108: E/AndroidRuntime(640): java.lang.RuntimeException: Unable to start activity ComponentInfo{priscillia.benkyo/priscillia.benkyo.TestLevel1}: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
11-03 17:43:11.108: E/AndroidRuntime(640):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
11-03 17:43:11.108: E/AndroidRuntime(640):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
11-03 17:43:11.108: E/AndroidRuntime(640):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
11-03 17:43:11.108: E/AndroidRuntime(640):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
11-03 17:43:11.108: E/AndroidRuntime(640):  at android.os.Handler.dispatchMessage(Handler.java:99)
11-03 17:43:11.108: E/AndroidRuntime(640):  at android.os.Looper.loop(Looper.java:137)
11-03 17:43:11.108: E/AndroidRuntime(640):  at android.app.ActivityThread.main(ActivityThread.java:4745)
11-03 17:43:11.108: E/AndroidRuntime(640):  at java.lang.reflect.Method.invokeNative(Native Method)
11-03 17:43:11.108: E/AndroidRuntime(640):  at java.lang.reflect.Method.invoke(Method.java:511)
11-03 17:43:11.108: E/AndroidRuntime(640):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
11-03 17:43:11.108: E/AndroidRuntime(640):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-03 17:43:11.108: E/AndroidRuntime(640):  at dalvik.system.NativeStart.main(Native Method)
11-03 17:43:11.108: E/AndroidRuntime(640): Caused by: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
11-03 17:43:11.108: E/AndroidRuntime(640):  at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251)
11-03 17:43:11.108: E/AndroidRuntime(640):  at java.util.ArrayList.get(ArrayList.java:304)
11-03 17:43:11.108: E/AndroidRuntime(640):  at priscillia.benkyo.TestLevel1.onCreate(TestLevel1.java:46)
11-03 17:43:11.108: E/AndroidRuntime(640):  at android.app.Activity.performCreate(Activity.java:5008)
11-03 17:43:11.108: E/AndroidRuntime(640):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
11-03 17:43:11.108: E/AndroidRuntime(640):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)

TestLevel1.java

public class TestLevel1 extends Activity {
    List<Question> quesList;
    int score=0;
    int qid;
    Question currentQ;
    TextView txtQuestion;
    RadioButton rda, rdb, rdc, rdd;
    Button butNext;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test_level1);
        DatabaseHelper db=new DatabaseHelper(this);
        quesList=db.getAllQuestions();
        currentQ=quesList.get(qid);
        txtQuestion=(TextView)findViewById(R.id.soal);
        rda=(RadioButton)findViewById(R.id.radio0);
        rdb=(RadioButton)findViewById(R.id.radio1);
        rdc=(RadioButton)findViewById(R.id.radio2);
        rdd=(RadioButton)findViewById(R.id.radio3);
        butNext=(Button)findViewById(R.id.lanjutBtn);
        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.GetCorr_Ans()+" "+answer.getText());
                    if(currentQ.GetCorr_Ans().equals(answer.getText()))
                    {
                        score++;
                        Log.d("score", "Your score"+score);
                    }
                    if(qid<5){                    
                        currentQ=quesList.get(qid);
                        setQuestionView();
                    }else{
                        Intent intent = new Intent(TestLevel1.this, Result.class);
                        Bundle b = new Bundle();
                        b.putInt("score", score); //Your score
                        intent.putExtras(b); //Put your score to your next Intent
                        startActivity(intent);
                        finish();
                    }
                }
            });
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.test_level1, menu);
        return true;
    }
    private void setQuestionView()
    {
        txtQuestion.setText(currentQ.GetSoal_Desc());
        rda.setText(currentQ.GetPilihan_A());
        rdb.setText(currentQ.GetPilihan_B());
        rdc.setText(currentQ.GetPilihan_C());
        rdd.setText(currentQ.GetPilihan_D());
        qid++;
    }
}

请帮我解决这个问题......

Answer 1

我猜数据库没有返回任何内容:

quesList=db.getAllQuestions();

因此，获取第一项(索引 0)的下一行失败:

currentQ=quesList.get(qid);

在获取第一个元素之前，您应该测试列表中是否有任何项目:

if (quesList.size() > 0) {
    // you can now get items
}