android – sqlite table not created when app is updated

Question:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.predmet_zapis);
    dbHelper = new DBHelper(this);

    ed1 = (EditText) findViewById(R.id.et_predmet);
    bt1 = (Button) findViewById(R.id.but1);
    bt1.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            bd = dbHelper.getWritableDatabase();
            ContentValues cv = new ContentValues();
            String chisl1 = ed1.getText().toString();
            cv.put("chisl", chisl1);
            long rowID = bd.insert("mypoints", null, cv);
            Log.d("LOG_TAG", "row inserted, ID = " + rowID);
            dbHelper.close();
        }
    });
}

public class DBHelper extends SQLiteOpenHelper {

public DBHelper(Context context) {
    // конструктор суперкласса
    super(context, "myDB", null, 1);
}

@Override
public void onCreate(SQLiteDatabase db) {
    // создаем таблицу с полями
    Log.d("123","cоздана БД");
    db.execSQL("create table mypoints ("
            + "id integer primary key autoincrement,"
            + "chisl text"+");");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}
}

I'm trying to create a database, but it's not being created. Writes "no such table: mypoints".

I deleted the application from the phone, reinstalled it – it worked, but after I decided to change the name of the table, it stopped working with the same error, why is that?

Answer:

onCreate is called when there is no database. When updating the application, the database already exists and onCreate is not called, therefore a new table is not created.

If you decide to change the structure of the database, then you need to increase the database version number in the parent constructor call:

super(context, "myDB", null, 2);

And add logic to the onUpgrade function: what to do to bring the old database to the new structure:

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if(oldVersion < 2) {
        db.execSQL("alter table mytable rename to mypoints;");
    }
}