why i am getting runtime error " QObject: Cannot create children for a parent that is in a different thread." ?

Qt embedded developer

i want to start and stop interrupt at 15 second interval when receive interrupt.
but i am getting runtime error
" QObject: Cannot create children for a parent that is in a different thread.
(Parent is QApplication(0x7efcfb20), parent's thread is QThread(0xc50bf8), current thread is QThread(0x68f006c8) "

How to resolve this error ?

#include "MainWindow.h"
#include "ui_MainWindow.h"
#include <QDebug>
#include <QTimer>
void gpo_handler()
{

    uint8_t itstatus;

    MainWindow m;


        // if( GPO_Activated == 1 )
        // {
        //GPO_Activated = 0;

           // qDebug()<<"RF write \n";
           // printf("RF write \n");
if(m.bStatus == true)
{
    if(m.elapsetime.elapsed()>15000)
    {
    BSP_NFCTAG_ConfigIT(0,ST25DV_GPO_ENABLE_MASK | ST25DV_GPO_RFWRITE_MASK );// field is on and off
     m.bStatus =false;
    }
}
    ST25_RETRY(BSP_NFCTAG_ReadITSTStatus_Dyn(0, &itstatus ));



        if( (itstatus & ST25DV_ITSTS_DYN_RFWRITE_MASK) == ST25DV_ITSTS_DYN_RFWRITE_MASK )
        {
            BSP_NFCTAG_ConfigIT(0,0);// field is on and off
            qDebug()<<"RF write \n";

            m.bStatus = true;
            m.elapsetime.start();

            //sleep(15);
           // BSP_NFCTAG_ConfigIT(0,ST25DV_GPO_ENABLE_MASK | ST25DV_GPO_RFWRITE_MASK );// field is on and off
        }


}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    // const ST25DV_PASSWD st25dv_i2c_password = {.MsbPasswd = 0, .LsbPasswd=0};
    bStatus = false;
     /* Init of the Type Tag 5 component (ST25DV-I2C) */
      if(BSP_NFCTAG_Init(0) != NFCTAG_OK);


     /* Present configuration password */
     //  BSP_NFCTAG_PresentI2CPassword(0, st25dv_i2c_password );

     /* Set GPO Configuration */

    BSP_NFCTAG_ConfigIT(0,ST25DV_GPO_ENABLE_MASK | ST25DV_GPO_RFWRITE_MASK );// field is on and off

   //  BSP_NFCTAG_ConfigIT(0,ST25DV_GPO_ENABLE_MASK | ST25DV_GPO_RFWRITE_MASK );// no
   //  BSP_NFCTAG_ConfigIT(0,ST25DV_GPO_ENABLE_MASK | ST25DV_GPO_RFGETMSG_MASK ); // No
   //  BSP_NFCTAG_ConfigIT(0,ST25DV_GPO_ENABLE_MASK | ST25DV_GPO_RFINTERRUPT_MASK ); // No
   //  BSP_NFCTAG_ConfigIT(0,ST25DV_GPO_ENABLE_MASK | ST25DV_GPO_RFPUTMSG_MASK );// NO
   //  BSP_NFCTAG_ConfigIT(0,ST25DV_GPO_ENABLE_MASK | ST25DV_GPO_RFACTIVITY_MASK );// field is on

     while(ST25DV_GPO_Init() != NFCTAG_OK);

     while(ST25DV_GPO_interrupt_init(&gpo_handler) != NFCTAG_OK);

   //  ST25DV_GPO_DeInit();


}

MainWindow::~MainWindow()
{
    delete ui;
}

jsulm

@Qt-embedded-developer said in why i am getting runtime error " QObject: Cannot create children for a parent that is in a different thread." ?:

MainWindow m;

Why do you create an instance of MainWindow in your gpo_handler()?!

Qt embedded developer

@jsulm to start and stop interrupt at 15 second while receive interrupt.

jsulm

@Qt-embedded-developer said in why i am getting runtime error " QObject: Cannot create children for a parent that is in a different thread." ?:

to start and stop interrupt at 15 second while receive interrupt.

You should contact the already existing MainWindow instance instead of creating a new MainWindow every time gpo_handler() is called...

Qt embedded developer

@jsulm How to create MainWindow instance in MainWindow class ? Please provide example

jsulm

@Qt-embedded-developer You create your MainWindow instance in main() already, right?
I suggest to do this:

MainWindow* mainWindowInstance{nullptr};

void gpo_handler()
{
    uint8_t itstatus;
    if (!mainWindowInstance) return;
    if(mainWindowInstance.bStatus == true)
...
}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    mainWindowInstance = this;

Qt embedded developer

@jsulm said in why i am getting runtime error " QObject: Cannot create children for a parent that is in a different thread." ?:

mainWindowInstance.bStatus

i got below error while i write above code

error: 'nullptr' was not declared in this scope
MainWindow* mainWindowInstance{nullptr};
^

jsulm

@Qt-embedded-developer What compiler do you use?!
C++11 compiler should know what nullptr is, but you also can simply use 0.