InputStream 不想从文本文件 android studio 中读取

Question

我在 java 中使用 android 编程时遇到问题，因为它不想从文本文件中读取。问题是按钮没有添加我试图在异步类中执行的文本。此外，显示文本的按钮不起作用，因为当我按下按钮时，应用程序停止工作。

节目简介：

应用程序从一个从微调器发送到 gameAction 的值开始，然后它将调用文本文件上的名称，该名称将加载到数组列表中的字符串中，即 QuestionBox 类。最后它将在 GameAction 类中提出问题。

如果有不清楚的地方，请发表评论。任何帮助表示赞赏！请原谅我添加了很多代码，但由于不知道该怎么做，我添加了它。

public class QuestionBox extends AsyncTask<Object, Void, Object>{

private Context context;
private Callback callback;
private List<Question> mQuestions;
public QuestionBox(Context context,Callback callback)
{
    mQuestions = new ArrayList<Question>();
    this.callback=callback;
    this.context= context;

}
public  Callback getCallback(){

    return callback;
}


@Override
protected Object doInBackground(Object... params) {

InputStream iS = null;
    try {
        iS = context.getAssets().open("hogskoleprovet.txt");
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    //System.out.println("Hit kom du");
    BufferedReader reader = new BufferedReader(new InputStreamReader(iS));




    String question, answer, answerOne, answerTwo, answerThree, answerFour;



    try {
        while (reader.readLine() != null) {

            //reading some lines from resource file
            question = reader.readLine();
            answer = reader.readLine();
            answerOne = reader.readLine();
            answerTwo = reader.readLine();
            answerThree = reader.readLine();

            answerFour = reader.readLine();
            Question q = new Question(question, answer, answerOne, answerTwo, answerThree, answerFour);
            mQuestions.add(q);

            break;
        }
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    try {
        reader.close();
        System.out.println("Hit kom du3");
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    return 0;
}

public interface Callback{
    public void notify_result(List<Question> question_list);





    }





@Override
protected void onPostExecute(Object result) {
    // TODO Auto-generated method stub
    super.onPostExecute(result);


}






public int getQuestionsLeft() {
    return mQuestions.size();
}

public Question getRandomQuestion() {

    Random random = new Random();
    int index = random.nextInt(mQuestions.size());
    Question newQuestion = mQuestions.get(index);
    mQuestions.remove(index);
    return newQuestion;
}

}

这是字符串将被发送到的另一种方法：

公共类 gameAction 扩展 ActionBarActivity 实现 QuestionBox.Callback{

private QuestionBox mQuestionBox;
private Question mCurrentQuestion;
private Context context;
private Callback callback;

@Override
public void notify_result(List<Question> question_list) {

}



 protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_game_action);
    //Kod som kollar vad som skickades med när aktiviteten startades
    Intent callingIntent = getIntent();
    int index = callingIntent.getIntExtra("INDEX",0);

    //Bestäm filnamn beroende på vad som skickades med


    if(index==0){


        mQuestionBox =new QuestionBox(getApplicationContext(), this);
        mQuestionBox.execute("hogskoleprovet.txt");

    }
    else {
        if (index == 1 ) {
            mQuestionBox =new QuestionBox(getApplicationContext(), this);
            mQuestionBox.execute("hogskoleprovet.txt");



        } else if (index == 1) {
            mQuestionBox =new QuestionBox(getApplicationContext(), this);
            mQuestionBox.execute("hogskoleprovet.txt");



        } else if (index == 2) {
            mQuestionBox =new QuestionBox(getApplicationContext(), this);
            mQuestionBox.execute("hogskoleprovet.txt");



        }
    }







}


public void setNewQuestion()
{

    //Hämta en slumpmässig fråga från vår QuestionBox
    //och lagra den i mCurrentQuestion
    mCurrentQuestion = mQuestionBox.getRandomQuestion();


    //Se till så att textfält och knappar visar den aktuella
    //frågan

    TextView questionTextView = (TextView) findViewById(R.id.questionTextView);
    questionTextView.setText(mCurrentQuestion.getQuestion());


    Button buttonOne = (Button) findViewById(R.id.buttonOne);
    buttonOne.setText(mCurrentQuestion.getOptionOne());


    Button buttonTwo = (Button) findViewById(R.id.buttonTwo);
    buttonTwo.setText(mCurrentQuestion.getOptionTwo());


    Button buttonThree = (Button) findViewById(R.id.buttonThree);
    buttonThree.setText(mCurrentQuestion.getOptionThree());

    Button buttonFour = (Button) findViewById(R.id.buttonFour);
    buttonFour.setText(mCurrentQuestion.getOptionFour());

    Button buttonNew = (Button) findViewById(R.id.buttonNew);

    buttonOne.setEnabled(true);
    buttonTwo.setEnabled(true);
    buttonThree.setEnabled(true);
    buttonFour.setEnabled(true);


    buttonNew.setVisibility(View.INVISIBLE);

    buttonOne.setText(mCurrentQuestion.getOptionOne());
    buttonTwo.setText(mCurrentQuestion.getOptionTwo());
    buttonThree.setText(mCurrentQuestion.getOptionThree());
    buttonFour.setText(mCurrentQuestion.getOptionFour());


}
public void quitTheGame(View v){

    Intent intent = new Intent (this, MainActivity.class);
    Button butttonQuit =  (Button) findViewById(R.id.buttonFive);
    startActivity(intent);

}




public void answerClick(View V)
{
    Button answerButton = (Button)V;
    Button buttonOne = (Button) findViewById(R.id.buttonOne);
    buttonOne.setText(mCurrentQuestion.getOptionOne());


    Button buttonTwo = (Button) findViewById(R.id.buttonTwo);
    buttonTwo.setText(mCurrentQuestion.getOptionTwo());


    Button buttonThree = (Button) findViewById(R.id.buttonThree);
    buttonThree.setText(mCurrentQuestion.getOptionThree());

    Button buttonFour = (Button) findViewById(R.id.buttonFour);
    buttonFour.setText(mCurrentQuestion.getOptionFour());

    Button buttonNew = (Button) findViewById(R.id.buttonNew);



    buttonOne.setEnabled(false);
    buttonTwo.setEnabled(false);
    buttonThree.setEnabled(false);
    buttonFour.setEnabled(false);


    buttonNew.setVisibility(View.VISIBLE);



}


public void newClick(View v){

    if(mQuestionBox.getQuestionsLeft()>0){
        setNewQuestion();

    }


    else
    {
        Context context = getApplicationContext();
        String text = "Slut på frågor!";
        int duration = Toast.LENGTH_SHORT;

        Toast toast = Toast.makeText(context, text, duration);
        toast.show();

    }

}






@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

}

这里是给正确选项提供答案的类：

包 com.example.arnpet.ultimatehogskoleprovet;

public class Question {

private String question;//Lagrar frågan

private String optionOne; //Lagrar svarsalternativ

private String optionTwo;

private String optionThree;

private String optionFour;

private String correctAnswer; //Lagrar det korrekta svaret

//控制者

public Question (String question, String optionOne, String optionTwo,
                 String optionThree, String optionFour, String correctAnswer)
{
    this.question = question;
    this.optionOne = optionOne;
    this.optionTwo = optionTwo;
    this.optionThree = optionThree;
    this.optionFour = optionFour;





}

public String getQuestion() {
    return question;
}

public String getOptionOne() {
    return optionOne;
}

public String getOptionTwo() {
    return optionTwo;
}

public String getOptionThree() {
    return optionThree;
}

public String getOptionFour() {
    return optionFour;
}

}

Answer 1

while (reader.readLine() != null)

在这里，您正在读取文件的一行并将其丢弃。不是你想要的，除非你的文件结构很奇怪，经常带有可忽略的垃圾行。

通常的循环如下所示：

while ((line = reader.readLine()) != null)

然后在受控块中使用line。

其次，这是您检查 null 的唯一地方，但您还有其他几个 readLine() 调用，其中任何一个都可以返回 null。因此，您稍后会在代码中冒一些 NPE 风险。