QT SQLite “No query Unable to fetch row” when try to build for android

Hasibul Hasan Chowdhury

My code work fine for desktop but give this error when run on android emulator. Where is the problem ?

the_

@Hasibul-Hasan-Chowdhury
the USB crystall ball is broken, sorry

can you please give a little bit more information about how you try to open the database and execute your query (maybe the relevant piece of code?)

Hasibul Hasan Chowdhury

@the_ Thank you for your response. Here is my code
#include "databasemanager.h"

DatabaseManager::DatabaseManager()
{
openDB();
}

DatabaseManager::~DatabaseManager()
{
//close database after finish
db.close ();
}

QSqlDatabase DatabaseManager::getDB()
{
return db;
}

QSqlQuery *DatabaseManager::getQuery()
{
return query;
}

void DatabaseManager::openDB()
{
//load database driver on create
db = QSqlDatabase::addDatabase ("QSQLITE");

//loading existing databse
//db.setDatabaseName ("HCT_CMS.db");
db.setDatabaseName ("./HCT_CMS.db");

//opening database
db.open ();

//try connect to database
if(db.isOpen ()){
    qDebug() << "Database connected.";
} else {
    qDebug() << db.lastError ();
}

//query connected to specific database
query = new QSqlQuery(db);

}

Hasibul Hasan Chowdhury

@Hasibul-Hasan-Chowdhury
void Dialog::login_to_System()
{
//get user inputs
QString user_name = ui->txt_username->text ();
QString pass = ui->txt_password->text ();

//query statement for match username and password
const QString checkstmnt = "SELECT Username, Password FROM administrator WHERE "
                           "username = \'" + user_name + "\' AND password = \'" + pass + "\'";

//prepare statement
dbm->getQuery ()->prepare (checkstmnt);

//if execute query successful or match with database
if(dbm->getQuery ()->exec ()){

    //check if value is exists
    if(dbm->getQuery ()->next ()){

        //show the main window after successfully logged in to system
        MainWindow *mwindow = new MainWindow();
        mwindow->show ();

        //close the login window
        this->close ();

        //clear value
        user_name.clear ();
        pass.clear ();

    } else {
        QMessageBox::critical (this, "Error !!!", "Wrong username or password. Try again.");
    }
} else {
    QMessageBox::critical (this, "Error !!!", dbm->getQuery ()->lastError ().text ());
    qDebug() << dbm->getQuery ()->lastError ().text ();
}

}

the_

@Hasibul-Hasan-Chowdhury

before reading the rest of the code, your sql query is widely open for injections. please read how to use QSqlQuery::prepare() correctly.

NEVER pass user input directly to a sql query

J.Hilk

My usb-Crystalball tells me this:

db.setDatabaseName ("./HCT_CMS.db");

you don't have to permission to read/write on your Android device. Check your manifest and if you're using api 24+ check your App-Settings on your device after installlation.

the_

@Hasibul-Hasan-Chowdhury

Did you check if you already got an error message when trying to open the database?

@J-Hilk I have never written code for Android but when trying to open/write a sqlite db to a place without write perissions on windows it would tell somethin like "out of memory". Same for Android?

J.Hilk

@the_ said in QT SQLite “No query Unable to fetch row” when try to build for android:

@J-Hilk I have never written code for Android but when trying to open/write a sqlite db to a place without write perissions on windows it would tell somethin like "out of memory". Same for Android?

It's been a while since I wrote SQL for android.
But if memory serves me right, than there is no specific read/write access error. I believe I had no "our of memory" error but indeed the "unable to fetch row" one.

SGaist

Hi,

IIRC, the out of memory error is the error text returned by SQLite.

In any case, @J-Hilk is right, the path is wrong for Android.

QStandardPaths::writableLocation with QStandardPaths::AppDataLocation is the safest way.