problems with running asyncTask in android studio java

问题

I have problems with asyncTask in android programming. I am trying to load a text file in a background thread which is asyncTask. First of all, in my application I send a variable from a class which is controlled by an array-list which is later controlled by a button in a xml-file to the asyncTask class because it chooses an index throug a spinner. When it comes to background thread class it fails since I do not know that part very well. If something was unclear please ask since I am beginner in android programming. Any help is appreciated!

Here is the code for sending a variable:

protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_game_action);

    Intent callingIntent = getIntent();
    int index = callingIntent.getIntExtra("INDEX",0);

    if(index==0){

        fileReader_async=new FileReader_async(getApplicationContext(), this);
        fileReader_async.execute("hogskoleprovet.txt");

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

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


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


        }
    }

    setNewQuestion();



}

Here is the async-Class:

package com.example.arnpet.ultimatehogskoleprovet;

import android.content.Context;
import android.os.AsyncTask;
import com.example.arnpet.ultimatehogskoleprovet.Question;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import javax.security.auth.callback.Callback;

public class FileReader_async extends AsyncTask {
private Context context;
private Callback callback;
private List<Question> mQuestions;
public FileReader_async(Context context,Callback callback)
{
    this.callback=callback;
}
@Override
protected Object doInBackground(Object... params) {
    InputStream iS = null;
    try {
        iS = context.getAssets().open("hogskoleprovet");
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    BufferedReader reader = new BufferedReader(new InputStreamReader(iS));

    mQuestions = new ArrayList<Question>();


    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();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return 0;
}
@Override
protected void onPostExecute(Object result) {
    // TODO Auto-generated method stub
    super.onPostExecute(result);
    callback.notify_result(mQuestions);
}
public interface Callback {

    public void notify_result(List<Question> question_list);


}
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;

}

}

Here is the error-log:

05-02 09:04:28.823  29549-29549/com.example.arnpet.ultimatehogskoleprovet E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.arnpet.ultimatehogskoleprovet, PID: 29549
java.lang.IllegalStateException: Could not execute method of the activity
        at android.view.View$1.onClick(View.java:3969)
        at android.view.View.performClick(View.java:4637)
        at android.view.View$PerformClick.run(View.java:19422)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5479)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at android.view.View$1.onClick(View.java:3964)
android.view.View.performClick(View.java:4637)
at android.view.View$PerformClick.run(View.java:19422)

            

来源：https://stackoverflow.com/questions/29999620/problems-with-running-asynctask-in-android-studio-java