Error: working with QThreads

SujaMM

I'm getting this error while ussing QThreads:

QObject: Cannot create children for a parent that is in a different thread.
(Parent is QNetworkAccessManager(0x15694420), parent's thread is QThread(0x15670d00), current thread is CaptureThread(0x156f0ea8)

I'm using an Api to save and get data from the Data Base, but when I try to save some information in the Thread I got that Error.

Can some help me out wiht this problem.

mcosta

Hi and welcome to devnet,

as the compiler says you're trying to create an Object passing a parent belonging to a different thread (usually is this).

Can you show your code??

SujaMM

Ok, this it's the header of the QThread.

#ifndef CAPTURETHREAD_H
#define CAPTURETHREAD_H

#include <QThread>
#include <QMutex>
#include <QWaitCondition>
#include <QJsonObject>
#include "api.h"
class CaptureThread : public QThread
{
    Q_OBJECT
public:
       explicit CaptureThread(Api *capi, QObject *parent = 0);
       void run();
       void pause();
       void resume();
       bool flagpause;
       bool Stop;
       int countTime;
       QMutex sync;
       QWaitCondition pauseCond;
       QString url;
       Api* api;
       QJsonObject jsonUser;
       QJsonObject jsonSession;
       int idTask;
signals:
       void counTimeChange(int countTime);
};

#endif // CAPTURETHREAD_H

Api it's the class with the methods to access the database through an api.

The implementation

#include "capturethread.h"
#include <QDesktopWidget>
#include <QApplication>
#include <QDir>
#include <QDate>

CaptureThread::CaptureThread(Api *capi, QObject *parent):
    QThread(parent)
{
    this->countTime = 0;
    this->api = capi;
}

void CaptureThread::run(){

    while (true) {
           api->createLog(api->jsonUser["id"].toInt(),api->jsonSession["id"].toInt());
           this->msleep(60000);
           QDesktopWidget* dw = QApplication::desktop();
           QPixmap pixmap = QPixmap::grabWindow( dw->winId(), 0, 0, dw->width(), dw->height() );

           QDir mDir(QDir::homePath());
           QString format = "jpg";
           QString filename = "/screenshot_" + QString::number(QDate::currentDate().year())+ "_"
                   +QString::number(QDate::currentDate().month())+ "_"
                   +QString::number(QDate::currentDate().day())+ "_"
                   +QString::number(QTime::currentTime().hour())+ "_"
                   +QString::number(QTime::currentTime().minute())+ "_"
                   +QString::number(QTime::currentTime().second());
           QString mPath = QDir::homePath() + "/user";
           if (!mDir.exists(mPath))
                mDir.mkpath(mPath);
           pixmap.save(mPath+filename+".jpg", format.toLatin1().constData());
           this->url = mPath+filename+".jpg";
           api->closeLog(api->jsonUser["id"].toInt(),api->jsonLog["id"].toInt(), url);
           this->countTime ++;
           emit counTimeChange(this->countTime);
           sync.lock();
           if(flagpause)
                 pauseCond.wait(&sync);
           sync.unlock();
       }
}

void CaptureThread::pause() {
        sync.lock();
        flagpause = true;
        sync.unlock();
}

void CaptureThread::resume() {
        sync.lock();
        flagpause = false;
        sync.unlock();
        pauseCond.wakeAll();
}

The main thread, the class task

 capThread = new CaptureThread(currentapi,this);
 . . . . 
 void Task::on_btnStart_clicked()
 {
     capThread->flagpause = false;
     capThread->resume();
     capThread->start();
 }

SujaMM

I fix this problem with signals and slots, but I firts create what a call a log, and after one minute a close that log.

I'm getting this error while closing the log

QEventLoop::exec: instance 0x8d4418 has already called exec()