Android crashes to previous screen debug in the post

Question

I was adding a list view to my database when in the end the database list view windows opens and crashes

Do you have any idea what this crash code mean? I can add code later if you need it

(Edit still no luck finding anything that could throw this command) Can you check with a command any way?

Database form:

 package com.example.laivumusis;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import androidx.annotation.Nullable;
import com.example.laivumusis.KlausimuContracts.*;

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

public class KlausimynoDatabaseHelper extends SQLiteOpenHelper {

    private static final String DATABASE_NAME = "Klausimynas.db";
    private static final int DATABASE_VERSION = 1;

    private SQLiteDatabase db;

    public KlausimynoDatabaseHelper(@Nullable 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 " +
                KlausimuLentele.TABLE_NAME + " ( " +
                KlausimuLentele._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                KlausimuLentele.COLUMN_QUESTION + " TEXT, " +
                KlausimuLentele.COLLUMN_OPTION1 + " TEXT, " +
                KlausimuLentele.COLLUMN_OPTION2 + " TEXT, " +
                KlausimuLentele.COLLUMN_OPTION3 + " TEXT, " +
                KlausimuLentele.COLLUMN_ANSWER_NR + " INTEGER" +
                ")";


        db.execSQL(SQL_CREATE_QUESTIONS_TABLE);
        fillKlausimuLentele();

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + KlausimuLentele.TABLE_NAME);
        onCreate(db);
    }
    public boolean addData (String pasirinkimas1){
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(KlausimuLentele.COLLUMN_OPTION1, pasirinkimas1);

        long result = db.insert(KlausimuLentele.TABLE_NAME, null, contentValues);

                if (result == -1){
                    return false;
                }else{
                    return true;
                }
    }

    public Cursor getListContents() {
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor data = db.rawQuery("SELECT * FROM " + KlausimuLentele.TABLE_NAME,null );
        return data;
    }


    private void fillKlausimuLentele() {
        Klausimai q1 = new Klausimai("Kelintais metais buvo išleista java proogramavimo kalba?", "1991", "1995", "1989", 1);
        addQuestion(q1);
        Klausimai q2 = new Klausimai("Ar destytojas pasigailės mūsų?", "Priklauso nuo darbo", "Priklauso nuo pingų", "Prklauso nuo nuotaikos", 1);
        addQuestion(q2);
        Klausimai q3 = new Klausimai("Kai sunervina žaidimas koks geriausias būdas iš jo išeiti?", "Alt+F4", "Quit To desktop", "Ištraukti maitinimo laida",1);
        addQuestion(q3);
        Klausimai q4 = new Klausimai("A is correct again", "A", "B", "C", 1);
        addQuestion(q4);
        Klausimai q5 = new Klausimai("B is correct agian", "A", "B", "C", 2);
        addQuestion(q5);
    }

    private void addQuestion(Klausimai klausimai) {
        ContentValues cv = new ContentValues();
        cv.put(KlausimuLentele.COLUMN_QUESTION, klausimai.getKlausimas());
        cv.put(KlausimuLentele.COLLUMN_OPTION1, klausimai.getPasirinkimas1());
        cv.put(KlausimuLentele.COLLUMN_OPTION2, klausimai.getPasirinkimas2());
        cv.put(KlausimuLentele.COLLUMN_OPTION3, klausimai.getPasirinkimas3());
        cv.put(KlausimuLentele.COLLUMN_ANSWER_NR, klausimai.getAtsakymoNr());
        db.insert(KlausimuLentele.TABLE_NAME, null, cv);

    }

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

        if (c.moveToFirst()) {
            do {
                Klausimai klausimai = new Klausimai();
                klausimai.setKlausimas(c.getString(c.getColumnIndex(KlausimuLentele.COLUMN_QUESTION)));
                klausimai.setPasirinkimas1(c.getString(c.getColumnIndex(KlausimuLentele.COLLUMN_OPTION1)));
                klausimai.setPasirinkimas2(c.getString(c.getColumnIndex(KlausimuLentele.COLLUMN_OPTION2)));
                klausimai.setPasirinkimas3(c.getString(c.getColumnIndex(KlausimuLentele.COLLUMN_OPTION3)));
                klausimai.setAtsakymoNr(c.getInt(c.getColumnIndex(KlausimuLentele.COLLUMN_ANSWER_NR)));
                klausimuSarasas.add(klausimai);
            } while (c.moveToNext());
        }

        c.close();
        return klausimuSarasas;

    }
}

But i think the problem is in here because this is the form which crashes:

    package com.example.laivumusis;

import android.database.Cursor;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import java.util.ArrayList;

public class ViewListData extends AppCompatActivity {

    KlausimynoDatabaseHelper myDB;

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

        ListView listView = (ListView) findViewById(R.id.listView);
         myDB = new KlausimynoDatabaseHelper(this);

        ArrayList<String> theList = new ArrayList<>();
        Cursor data = myDB.getListContents();

        if (data.getCount() == 0) {
            Toast.makeText(ViewListData.this,"Database tuščias!",Toast.LENGTH_LONG).show();
        }else{
            while (data.moveToNext()){
                theList.add(data.getString(1));
                ListAdapter listAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1,theList);
                listView.setAdapter(listAdapter);
            }
        }
    }
}

Debug:

 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.laivumusis, PID: 3859
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference

Does this answer your question? [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — cutiko, May 08 '20 at 13:50

score 0 · Accepted Answer · answered May 08 '20 at 13:43

0

Your object seems to be null while converting to string. use the following to check if null:

if (obj !=null){
    //store in database

}

answered May 08 '20 at 13:43

mohammad jalili

187
2
10

1

Ok ill try find it – Lukas Kaščiukevičius May 08 '20 at 13:54

Android crashes to previous screen debug in the post

1 Answers1