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.