"Cannot resolve symbol" errors - Android Studio

Question

I am getting "cannot resolve symbol" on menu located under public boolean onCreateOptionsMenu(Menu menu). The same error shows up on action_settings located under public boolean onOptionsItemSelected(MenuItem item).

Here is the .java code:

package com.bignerdranch.android.geoquizz;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
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;

private Question[] mQuestionBank = new Question[] {
        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, false),
        new Question(R.string.question_asia, true),
};

    private int mCurrentIndex = 0;

    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();
    }

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

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

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

        mNextButton = (Button) findViewById(R.id.next_buton);
        mNextButton.setOnClickListener(new View.OnClickListener() {
                                           @Override
                                           public void onClick(View v) {
                                               updateQuestion();
                                           }
                                       });

        updateQuestion();

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.quiz, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item){
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

Here is my strings.xml code:

<resources>
    <string name="app_name">GeoQuizz</string>
    <string name="true_button">True</string>
    <string name="false_button">False</string>
    <string name="next_button">Next</string>
    <string name="action_settings">Settings</string>
    <string name="correct_toast">Correct!</string>
    <string name="incorrect_toast">Incorrect!</string>
    <string name="question_oceans">The Pacific Ocean is larger than the Atlantic Ocean.</string>
    <string name="question_mideast">The Suez Canal connects the Red Sea and the Indian Ocean.</string>
    <string name="question_africa">The source of the Nile River is in Egypt.</string>
    <string name="question_americas">The Amazon River is the longest river in the Americas.</string>
    <string name="question_asia">Lake Baikal is the world\'s oldest and deepest freshwater lake.</string>
</resources>

Answer 1

Make sure your quiz.xml is in the right directory -> res/menu folder

Answer 2

As the suggestion from here,

https://github.com/ribot/android-guidelines/blob/master/project_and_code_guidelines.md

First, you can set your id(with prefix 'menu_' to avoid confusing meaning) in your menu.xml

<menu>
    <item
        android:id="@+id/menu_setting"
        android:title="Done" />
</menu>

Second, Change the code in your onOptionsItemSelected() method

@Override
public boolean onOptionsItemSelected(MenuItem item){
    int id = item.getItemId();
    if (id == R.id.menu_setting) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}