[solved]I have a problem about the Qthread

[joeQ]

First my error is

QObject: Cannot create children for a parent that is in a different thread.
(Parent is QNativeSocketEngine(0xbbb9d0), parent's thread is QThread(0xbb1768),
current thread is QThread(0xbbc198)

and it is a running time error.and i also asked someone,he said, it is about my Qt version,and ,it will not have the problem when use the Qt 3.8,but my Qt is 5.4.0 . is it real about the Qt version? Thank you very much!

my code is:

main.cpp

#include <QCoreApplication>
#include "myserver.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    MyServer server;
    server.ServerStart();

    return a.exec();
}

myserver.h

#ifndef MYSERVER_H
#define MYSERVER_H

#include <QObject>
#include <QTcpServer>
#include <QTcpSocket>
#include <QAbstractSocket>
#include <QDebug>

class MyServer : public QTcpServer//inherit QTcpServer
{
    Q_OBJECT
public:
    explicit MyServer(QObject *parent = 0 );
    void ServerStart();
protected:
    void incomingConnection(int handl);
};

#endif // MYSERVER_H

myserver.cpp

#include "myserver.h"
#include "myclient.h"
MyServer::MyServer(QObject *parent):QTcpServer(parent)
{

}

void MyServer::ServerStart()
{
    if( this->listen(QHostAddress::Any,1234))
    {
        qDebug()<<"Connectioned!";
    }
    else
    {
        qDebug()<<"no Connection";
    }
}

void MyServer::incomingConnection(int handl)
{
    MyClient *client = new MyClient(this);
    client->setSocket(handl);
}

myclient.h

#ifndef MYCLIENT_H
#define MYCLIENT_H

#include <QObject>
#include <QTcpSocket>
#include <QThreadPool>

class MyClient : public QObject
{
    Q_OBJECT
public:
    explicit MyClient(QObject *parent = 0);
    void setSocket(int socketDescriptior);
signals:

public slots:
    void connected();
    void disconnected();
    void readyRead();
    void TaskResult(int Number);
private:
    QTcpSocket *socket;
    QThreadPool *threadPool;
};

#endif // MYCLIENT_H

myclient.cpp

#include <QThreadPool>
#include "myclient.h"
#include "mytask.h"

MyClient::MyClient(QObject *parent) : QObject(parent)
{
    QThreadPool::globalInstance()->setMaxThreadCount(5);
    //this->threadPool = new QThreadPool(this);
    //this->threadPool->setMaxThreadCount(5);
}

void MyClient::setSocket(int socketDescriptior)
{
    this->socket = new QTcpSocket(this);
    connect(socket,SIGNAL(connected()),this,SLOT(connected()));
    connect(socket,SIGNAL(disconnected()),this,SLOT(disconnected()));
    connect(socket,SIGNAL(readyRead()),this,SLOT(readyRead()));
    this->socket->setSocketDescriptor(socketDescriptior);
    qDebug()<<"Client connected!";
}

void MyClient::connected()
{
    qDebug()<<"Client connected event!";
}

void MyClient::disconnected()
{
    qDebug()<<"Client disconnected event!";
}

void MyClient::readyRead()
{
    qDebug()<<socket->readAll();
    MyTask *task = new MyTask();
    task->setAutoDelete(true);
    connect(task,SIGNAL(Result(int)),this,SLOT(TaskResult(int)),Qt::DirectConnection);
    QThreadPool::globalInstance()->start(task);
    //this->threadPool->start(task);
}

void MyClient::TaskResult(int Number)
{
    QByteArray buffer;
    buffer.append(tr("\r\nTask Result : "));
    buffer.append(QString::number(Number));
    this->socket->write(buffer);
}

mytask.h

#ifndef MYTASK_H
#define MYTASK_H
#include <QRunnable>
#include <QObject>
#include <QDebug>

class MyTask : public QObject,public QRunnable
{
    Q_OBJECT
public:
    MyTask();
signals:
    void Result(int iNumber);

protected:
    void run();
};

#endif // MYTASK_H

mytask.cpp

#include "mytask.h"

MyTask::MyTask()
{

}

void MyTask::run()
{
    qDebug()<<"Tesk Run...";
    int iNumber = 0;
    for(int i=0; i<100; ++i)
    {
        iNumber += i;
    }
    qDebug()<<"Task done!";
    emit Result(iNumber);
}

[mcosta]

@joeQ said:

QObject: Cannot create children for a parent that is in a different thread.
(Parent is QNativeSocketEngine(0xbbb9d0), parent's thread is QThread(0xbb1768),
current thread is QThread(0xbbc198)

The message is clear; to try to understand you can print the Thread identifiers.
The only strange thing I see in your code is

connect(task,SIGNAL(Result(int)),this,SLOT(TaskResult(int)),Qt::DirectConnection);

try to not use a DirectConnection, better QueuedConnection or Auto (the default)

[joeQ]

Very,Very,Very,Thank you.I am sorry about my error,and I am a new person about to learn Qt.ok, my problem is done. i will see document to know why.Thank you!

[mcosta]

How did you solved??

Posting the solution can help other people with the same problem

[joeQ]

@mcosta You told me,the problem is at here
connect(task,SIGNAL(Result(int)),this,SLOT(TaskResult(int)),Qt::DirectConnection);
so,i modified it
connect(task,SIGNAL(Result(int)),this,SLOT(TaskResult(int)));
and I see the document and i know why.
the document said:

*Qt::DirectConnection	
The slot is invoked immediately when the signal is emitted. The slot is executed *in the signalling thread*. 

*Qt::QueuedConnection	  
The slot is invoked when control returns to the event loop of the receiver's thread. The slot is executed in the receiver's thread.

*Qt::AutoConnection	
(Default) If the receiver lives in the thread that emits the signal, Qt::DirectConnection is used. Otherwise, Qt::QueuedConnection is used. The connection type is determined when the signal is emitted.

when i used the DirectConnection,the slot was executed in the signalling thread,and the signalling thread is another thread,and in mytask.cpp,so,I was wrong at here.

is it right about my said?

[mcosta]

Yes, Thank you