NullPointerException

#1

package com.bignerdranch.android.geoquiz;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class QuizActivity extends AppCompatActivity {

private Button mTrueButton;
private Button mFalseButon;
private Button mNextBuuttonn;
private TextView mQuestionTextView;

private Question [] mQuestionBank = new Question[]{
        new Question(R.string.question_australia, true),
        new Question(R.string.question_oceans, true),
        new Question(R.string.question_mideast, false),
        new Question(R.string.question_africa, false),
        new Question(R.string.question_americas, true),
        new Question(R.string.question_asia, true),
};

private int mCurrentIndex = 0;


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

    mQuestionTextView = (TextView) findViewById(R.id.question_text_view);


    mTrueButton = (Button) findViewById(R.id.true_button);
    mTrueButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            checkAnswer(true);


        }
    });
    mFalseButon = (Button) findViewById(R.id.false_button);
    mFalseButon.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
           checkAnswer(false);

        }
    });

    mNextBuuttonn = (Button) findViewById(R.id.next_button);
    mNextBuuttonn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mCurrentIndex = (mCurrentIndex + 1) % mQuestionBank.length;
          updateQuestion();
        }
    });

    updateQuestion();

}

private void updateQuestion(){
    int question = mQuestionBank[mCurrentIndex].getTextResId();
    mQuestionTextView.setText(question);

}

private void checkAnswer (boolean userPressedTrue) {
    boolean answerIsTrue = mQuestionBank[mCurrentIndex].isAnswertrue();
    int messageResId = 0;
    if(userPressedTrue == answerIsTrue) {
        messageResId = R.string.correct_toast;
    }
    else {
        messageResId = R.string.incorrect_toast;
    }

    Toast.makeText(this, messageResId, Toast.LENGTH_SHORT).show();
}

}

Caused by: java.lang.NullPointerException
at com.bignerdranch.android.geoquiz.QuizActivity.updateQuestion(QuizActivity.java:70)
at com.bignerdranch.android.geoquiz.QuizActivity.onCreate(QuizActivity.java:64)