My activity won't open while working with a SQLite database

Question

Currently following a YouTube tutorial regarding a Quiz App in Android that has SQLite integration. Link here: https://www.youtube.com/watch?v=pEDVdSUuWXE

I've been following him to the finest detail, but when I start my app on my emulator in Android Studio, the intended activity won't start when I press the button on the starting activity. Furthermore, my SQLite database won't insert the data hardcoded into it using the QuizActivity Java class.

Here is my code

QuizDBHelper.java

package com.faith.mobilequiz;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import com.faith.mobilequiz.QuizContract.*;

import java.util.ArrayList;
import java.util.List;

public class QuizDBHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "MobileQuiz.db";
    private static final int DATABASE_VERSION = 1;

    private SQLiteDatabase db;

     public QuizDBHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
         this.db = db;

        final String SQL_CREATE_QUESTIONS_TABLE = "CREATE TABLE " +
                QuestionsTable.TABLE_NAME + " ( " +
                QuestionsTable._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                QuestionsTable.COLUMN_QUESTION + " TEXT, " +
                QuestionsTable.COLUMN_OPTION1 + " TEXT, " +
                QuestionsTable.COLUMN_OPTION2 + " TEXT, " +
                QuestionsTable.COLUMN_OPTION3 + " TEXT, " +
                QuestionsTable.COLUMN_ANSWER_NUMBER + " INTEGER " +
                ")";

         db.execSQL(SQL_CREATE_QUESTIONS_TABLE);
         fillQuestionsTable();

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
          db.execSQL("DROP TABLE IF EXISTS " + QuestionsTable.TABLE_NAME);
          onCreate(db);
    }

    private void fillQuestionsTable() {
        Question q1 = new Question("A is correct", "A", "B", "C", 1);
        addQuestion(q1);
        Question q2 = new Question("B is correct", "A", "B", "C", 2);
        addQuestion(q2);
        Question q3 = new Question("C is correct", "A", "B", "C", 3);
        addQuestion(q3);
        Question q4 = new Question("A is correct again", "A", "B", "C", 1);
        addQuestion(q4);
        Question q5 = new Question("B is correct again", "A", "B", "C", 2);
        addQuestion(q5);
    }

    private void addQuestion(Question question) {
        ContentValues cv = new ContentValues();
        cv.put(QuestionsTable.COLUMN_QUESTION, question.getQuestion());
        cv.put(QuestionsTable.COLUMN_OPTION1, question.getOption1());
        cv.put(QuestionsTable.COLUMN_OPTION2, question.getOption2());
        cv.put(QuestionsTable.COLUMN_OPTION3, question.getOption3());
        cv.put(QuestionsTable.COLUMN_ANSWER_NUMBER, question.getAnswerNum());
        db.insert(QuestionsTable.TABLE_NAME, null, cv);
    }

    public List<Question> getAllQuestions() {
         List<Question> questionList = new ArrayList<>();
         db = getReadableDatabase();
         Cursor c = db.rawQuery("SELECT * FROM " + QuestionsTable.TABLE_NAME, null);

         if(c.moveToFirst()) {
             do {
                 Question question = new Question();
                 question.setQuestion(c.getString(c.getColumnIndex(QuestionsTable.COLUMN_QUESTION)));
                 question.setOption1(c.getString(c.getColumnIndex(QuestionsTable.COLUMN_OPTION1)));
                 question.setOption2(c.getString(c.getColumnIndex(QuestionsTable.COLUMN_OPTION2)));
                 question.setOption3(c.getString(c.getColumnIndex(QuestionsTable.COLUMN_OPTION3)));
                 question.setAnswerNum(c.getInt(c.getColumnIndex(QuestionsTable.COLUMN_ANSWER_NUMBER)));
                 questionList.add(question);
             } while(c.moveToNext());
         }

         c.close();
         return questionList;


    }
}

This is for QuizActivity.java

package com.faith.mobilequiz;

import android.content.res.ColorStateList;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;

import java.util.Collections;
import java.util.List;

public class QuizActivity extends AppCompatActivity {
    private TextView textViewQuestion;
    private TextView textViewScore;
    private TextView textViewQuestionCount;
    private TextView textViewTimer;
    private RadioGroup rbGroup;
    private RadioButton rb1;
    private RadioButton rb2;
    private RadioButton rb3;
    private Button buttonConfirmNext;

    private ColorStateList textColorDefaultRb;

    private List<Question> questionList;
    private int questionCounter;
    private int questionCountTotal;
    private Question currentQuestion;

    private int score;
    private boolean answered;

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

        textViewQuestion = findViewById(R.id.txtQuestion);
        textViewScore = findViewById(R.id.txtScore);
        textViewQuestionCount = findViewById(R.id.txtQuestionCount);
        textViewTimer = findViewById(R.id.txtTimer);
        rbGroup = findViewById(R.id.radioGroup);
        rb1 = findViewById(R.id.radioBtn1);
        rb2 = findViewById(R.id.radioBtn2);
        rb3 = findViewById(R.id.radioBtn3);
        buttonConfirmNext = findViewById(R.id.btnConfirmNext);

        textColorDefaultRb = rb1.getTextColors();

        QuizDBHelper dbHelper = new QuizDBHelper(this);
        questionList = dbHelper.getAllQuestions();
        questionCountTotal = questionList.size();
        Collections.shuffle(questionList);

        showNextQuestion();

    }

    private void showNextQuestion() {
        rb1.setTextColor(textColorDefaultRb);
        rb2.setTextColor(textColorDefaultRb);
        rb3.setTextColor(textColorDefaultRb);
        rbGroup.clearCheck();

        if(questionCounter < questionCountTotal) {
            currentQuestion = questionList.get(questionCounter);

            textViewQuestion.setText(currentQuestion.getQuestion());
            rb1.setText(currentQuestion.getOption1());
            rb2.setText(currentQuestion.getOption2());
            rb3.setText(currentQuestion.getOption3());
            questionCounter++;
            textViewQuestionCount.setText("Question: " + questionCounter + "/" + questionCountTotal);
            answered = false;
            buttonConfirmNext.setText("Confirm");

        } else {
            finishQuiz();
        }
    }

    private void finishQuiz() {
        finish();
    }
}

Is it something wrong with the query?

Answer 1

Is it something wrong with the query?

No.

The code you have, as copied and tested is fine.

Using an activity MainActivity comprised just of a button that can be clicked to start the quiz activity starts the quiz activity with a question.

Using the back button to return to the Main Activity and clicking the button display the next question.

In the main activity I have :-

public class MainActivity extends AppCompatActivity {
    Button mQuizButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        mQuizButton = this.findViewById(R.id.quizbutton);
        mQuizButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i = new Intent(MainActivity.this,QuizActivity.class);
                startActivity(i);
            }
        });
    }
}

What the issue could well be, is that you haven't defined the QuizActivity in the manifest.

e.g. :-

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".QuizActivity">
    </activity>
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

i.e. the you'd need

    <activity android:name=".QuizActivity">
    </activity>

To define the QuizActivity as an activity that can then be started.

Furthermore, my SQLite database won't insert the data hardcoded into it using the QuizActivity Java class.

It wouldn't if the Database is only accessed in the QuizActivity,

• noting that simply instantiating the QuizDBHelper doesn't actually create the database,

it's not until an attempt is made to get a writeable or readable database (this can be implicit with the SQliteDatabase method or can be explicit by using getWritableDatabase or getReadableDatabase) that the database is created and that the onCreate method is invoked the hard coded questions are then added (it does add them).

So I believe that you simply need to edit the manifest file AndroidManifest.xml accordingly.

It might be best to delete the Apps data or uninstall the App before rerunning it.