CODEWITHSUNDEEP
androidsqlite
sarvesh chavan
sarvesh chavan

Reputation: 33

SQLiteDatabase object

I have a Helper class which extends SQLiteOpenHelper in that i have four method

onCreate(SQLiteDatabase sqLiteDatabase)

onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1)

addquestions()

addingeachquestions(Questions question)// I also have one class named as Questions

I declared a SQLiteDatabase object as "db" under my Helperclass but when i make "db=sqLiteDatabase" in my onCreate & onUpgrade method it works fine but when i don't make statement "db=sqLiteDatabase" in my onCreate & onUpgrade method then logcat windows says null pointer exception at line 

"db.insert(Helperclass.TABLE_NAME, null, values);"

Here is my code

Helperclass.java

public class Helperclass extends SQLiteOpenHelper {
SQLiteDatabase db;
Context context;
Helperclass helperclass;
private static final String DATABASE_NAME = "DATABASE1";
private static final int DATABASE_VERSION = 52;
private static final String TABLE_NAME = "TABLE1";
private static final String UID = "_ID";
private static final String QUESTION = "QUESTION";
private static final String OPT1 = "OPT1";
private static final String OPT2 = "OPT2";
private static final String OPT3 = "OPT3";
private static final String ANSWER = "ANSWER";
private static final String CREATE_TABLE =
        "CREATE TABLE " + TABLE_NAME + " (" + UID + " INTEGER PRIMARY KEY, " + QUESTION + " VARCHAR(255), " + OPT1 + " VARCHAR(255), " + OPT2 + " VARCHAR(255), " + OPT3 + " VARCHAR(255), " + ANSWER + " VARCHAR(255));";
private static final String DROP_TABLE = "DROP TABLE IF EXISTS " + TABLE_NAME;      


public Helperclass(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    this.context = context;
    Toast.makeText(context, "constructor called", Toast.LENGTH_SHORT).show();
}

@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
    db = sqLiteDatabase;  //when i mentions this it works fine but when i don't it gives error. Why i have to mention this?         
    sqLiteDatabase.execSQL(CREATE_TABLE);
     addquestions();
}

@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
    db = sqLiteDatabase;  //when i mentions this it works fine but when i don't it gives error.
   sqLiteDatabase.execSQL(DROP_TABLE);
    onCreate(sqLiteDatabase);
}

public void addquestions() {
    Questions q1 = new Questions("what is your hobby?", "singing", "dancing", "reading", "sining");
    this.addingeachquestions(q1);
    Questions q2 = new Questions("how are you?", "fine", "good", "sad", "good");
    this.addingeachquestions(q2);
    Questions q3 = new Questions("whats your name?", "sam", "jhon", "alice", "sam");
    this.addingeachquestions(q3);
    Toast.makeText(context, "addquestion method called", Toast.LENGTH_SHORT).show();
}

private void addingeachquestions(Questions question) {
    ContentValues values = new ContentValues();
    values.put(Helperclass.QUESTION, question.getQUESTION());
    values.put(Helperclass.OPT1, question.getOPTA());
    values.put(Helperclass.OPT2, question.getOPTB());
    values.put(Helperclass.OPT3, question.getOPTC());
    values.put(Helperclass.ANSWER, question.getANSWER());
    db.insert(Helperclass.TABLE_NAME, null, values);
}

Upvotes: 0

Views: 627

Answers (4)

Tulsi
Tulsi

Reputation: 719

It is because instance of SQLiteDatabase, db is NULL.

You have absolutely no need to add db = sqLiteDatabase; in onCretae(SQLiteDatabase sqLiteDatabase) and onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) instead use the following code.

if (db ==null){ 
    db = this.getWritableDatabase();
 }

Upvotes: 0

priyanka kataria
priyanka kataria

Reputation: 417

Initialize db while calling your helper class:-

Helperclass helperClassObj = new Helperclass(context);
db = helperClassObj.getWritableDatabase();

Upvotes: 0

Meenal
Meenal

Reputation: 2877

You have to get object of Db in "addingeachquestions" method like this :

SQLiteDatabase db = this.getWritableDatabase();

or

db = this.getWritableDatabase();

Upvotes: 0

ρяσѕρєя K
ρяσѕρєя K

Reputation: 132982

No need to add db = sqLiteDatabase; line in onCreate. call getWritableDatabase method to initialize dbobject before using it.like before calling insert method in addingeachquestions method call getWritableDatabase():

db=getWritableDatabase();
db.insert(Helperclass.TABLE_NAME, null, values);

Upvotes: 2

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