App Crashes on Listing 2.7

1

The app crashes and the issue seems to be this line of code

mQuestionTextView.setText(question);

When I gray it out the app will run. I look at the similar issues on this forum but can’t figure it out.

package com.example.grady.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 mFalseButton;

private Button mNextButton;
private TextView mQuestionTextView;

//question array
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, true),
    new Question(R.string.question_africa, true),
    new Question(R.string.question_americas, true),
    new Question(R.string.question_australia, true)
};

private int mCurrentIndex = 0;

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

    //load the question
    mQuestionTextView = (TextView) findViewById(R.id.question_text_view);
    int question = mQuestionBank[mCurrentIndex].getTextResId();
    //mQuestionTextView.setText(question);

    mTrueButton = (Button) findViewById(R.id.true_button);
    mTrueButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Toast.makeText(QuizActivity.this, R.string.correct_toast, Toast.LENGTH_SHORT).show();
        }
    });

    mFalseButton = (Button) findViewById(R.id.false_button);
    mFalseButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Toast.makeText(QuizActivity.this, R.string.incorrect_toast, Toast.LENGTH_SHORT).show();
        }
    });

}

}

XML:

?xml version=“1.0” encoding=“utf-8”?>

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/question_text_view"
    android:padding="24dp" />

<LinearLayout
    android:orientation="horizontal"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    >

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/true_button"
        android:text="@string/true_button"/>

    <Button
        android:text="@string/false_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/false_button"/>
</LinearLayout>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/next_button"
    android:text="@string/next_button"/>
2

Take a look at my code but ignore the life cycle stuff. Maybe it will help. Eventually you will need to increment and decrement the index so I mad separate methods for them. Let me know if this helps. Nick

package com.bignerdranch.android.geoquiz;

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

import static java.lang.System.*;

public class QuizActivity extends AppCompatActivity
{
private static final String TAG = “QuizActivity”;

// Make all the UI Wizards known in the Main Class
private TextView    mQuestionTextView;
private ImageButton mPrevButton;
private ImageButton mNextButton;
private Button      mTrueButton;
private Button      mFalseButton;

 // Create a Question Array
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),
        };
// Get the array length
private int maxCurrentIndex = mQuestionBank.length;
// Initialize the Current Index Value
private int mCurrentIndex = 0;

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    Log.d(TAG, "onCreate(Bundle) called");
    setContentView(R.layout.activity_quiz);

    // Instantiate the Text View, Load the initial text, Start an On-Click Listener
    mQuestionTextView = (TextView) findViewById(R.id.question_text_view);
    mQuestionTextView.setText(R.string.text_view);
    mQuestionTextView.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            incrementQuestion();
        }
    });

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

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

    mPrevButton = (ImageButton) findViewById(R.id.prev_button);
    mPrevButton.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            if(mCurrentIndex == 0) mCurrentIndex = maxCurrentIndex;
            decrementQuestion();
        }
    });

    mNextButton = (ImageButton) findViewById(R.id.next_button);
    mNextButton.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            incrementQuestion();
        }
    });
}

private void incrementQuestion()
{
    mCurrentIndex = (mCurrentIndex +1) % maxCurrentIndex;
    int question  = mQuestionBank[mCurrentIndex].getTextResId();
    mQuestionTextView.setText(question);
}

private void decrementQuestion()
{
    mCurrentIndex = (mCurrentIndex - 1) % maxCurrentIndex;
    int question  = mQuestionBank[mCurrentIndex].getTextResId();
    mQuestionTextView.setText(question);
}

private void checkAnswer(boolean userPressedTrue)
{
    boolean answerIsTrue = mQuestionBank[mCurrentIndex].isAnswerTrue();
    int messageResId;

    if (userPressedTrue == answerIsTrue)
    {
        messageResId = R.string.correct_toast;
    } else
    {
        messageResId = R.string.incorrect_toast;
    }
    Toast.makeText(this, messageResId, Toast.LENGTH_SHORT).show();
}

// LIFE CYCLE METHODS

// @Override
public void OnStart()
{
super.onStart();
Log.d(TAG, “onStart() called”);
}
// @Override
public void OnResume()
{
super.onResume();
Log.d(TAG, “onResume() called”);
}
// @Override
public void OnPause()
{
super.onPause();
Log.d(TAG, “onPause() called”);
}
// @Override
public void OnStop()
{
super.onStop();
Log.d(TAG, “onStop() called”);
}
// @Override
public void OnDestroy()
{
super.onDestroy();
Log.d(TAG, “onDestroy() called”);
}
}