Qt 参数计数不匹配QSqlQuery

连接到我的数据库时，我想将数据发送到数据库中（我使用PHPMyAdmin online），但出现了一个错误

参数计数不匹配

db = QSqlDatabase::addDatabase("QSQLITE");  //this is the driver for SQL Lite
    db.setPort(3306);
    db.setHostName("sql2.freemysqlhosting.net");
    db.setPassword("****");
    db.setUserName("name");
    db.setConnectOptions();
    db.setDatabaseName("name");
    if(!db.open())
        ui->label->setText("<font color='red'>Failed to connect to database.</font>");
    else
        ui->label->setText("<font color='green'>Connected to database.</font>");

我怎样才能解决这个问题

QSqlQuery qsr(db);
qsr.prepare("INSERT INTO mytab (machine_id, operator_id) VALUES(:machine_id, :operator_id)");
    qsr.bindValue(":machine_id",ui->lineEdit->text());
    qsr.bindValue(":operator_id",ui->lineEdit_Operator_ID->text());
    if(qsr.exec())
        QMessageBox::information(this, "State","Saved",QMessageBox::Ok);
    else
        QMessageBox::information(this, "State", qsr.lastError().text(),QMessageBox::Ok);