Qt event emit inside thread not working properly

[sujith D]

void loaddepth::run(){
   
 
    QString file_name=this->filename;
    int day=this->day_no;
    int depth=this->deepth_no;
 
    QFile *file=new QFile(file_name);
    QTextStream in(file);
    file->open(QIODevice::ReadOnly | QIODevice::Text);
    const auto size = file->size();

     QStringList strList;
     bool flag=false;


        QStringList list;
        int line=0;
        int day_count=0;

        while(!in.atEnd()&&day_count<=day)
        {
            QString str=in.readLine().simplified();
            QStringList list=str.split(' ');

            if(list.count()==3){

                if(flag){
                    **emit readStatusChanged(this->file_no,list[0],list[1],list[2].toDouble());**

                }
 

 
            } else if(list.count()==1){

                if(list[0].toInt()!=depth&&flag==true){
                    qDebug()<<"b4 senting";
           }

                if(list[0].toInt()==depth){

                        flag=true;

                }

            }

   line++;
        }


}
 ******************************
connect(fileData1,SIGNAL(readStatusChanged(int,QString,QString,double)),this,SLOT(onReadStatusChanged(int,QString,QString,double)));

**event emits is not triggering inside the thread loop.**

[Christian Ehrlicher]

Did you check if the connect is successful and if you really emit the signal? Please show us where you connect the signal/slot connection.

[sujith D]

@Christian-Ehrlicher ya emit works only outside while loop. it doesn't work inside the loop.

connect(fileData1,SIGNAL(readStatusChanged(int,QString,QString,double)),this,SLOT(onReadStatusChanged(int,QString,QString,double)));

[Christian Ehrlicher]

@sujith-D said in Qt event emit inside thread not working properly:

ya emit works only outside while loop. it doesn't work inside the loop.

Again: how did you check that the signal is emitted? Did you added a breakpoint? Or a debug output?

And you still did not check the return value of connect() and did not show us the code around the connect on how you instantiate the class etc.

[sujith D]

@Christian-Ehrlicher

I do qDebug(), and its output.

[Christian Ehrlicher]

@sujith-D said in Qt event emit inside thread not working properly:

I do qDebug(), and its output.

Again: please show us more code, best a minimal example so we can try to reproduce it.

[sujith D]

@Christian-Ehrlicher
Calling thread from module2. Declared signals and slots in corresponding header files.
I don't know why the same event not working inside the loop during the file read.

Module2::Module2(QWidget *parent) :
    QWidget(parent),
    rect(0),
    ui(new Ui::Module2),
    scaleFactor(1),
    mapDim(1500)
{
    fileData1=new loaddepth(this);
 fileData1->filename=QCoreApplication::applicationDirPath()+"/../project3DUnderWater/0.txt";
fileData1->deepth_no=1;
connect(fileData1,SIGNAL(readStatusChanged(int,QString,QString,double)),this,SLOT(onReadStatusChanged(int,QString,QString,double)));
    connect(fileData1,SIGNAL(ReadFileCompleted(int,QJsonObject)),this,SLOT(onReadFileCompleted(int,QJsonObject)));
fileData1->start();

}

void Module2::onReadStatusChanged(int file_no,QString y,QString x,double z ){
    qDebug()<<"file_no"<<file_no;

}

void Module2::onReadFileCompleted(int file_no,QJsonObject json){

 qDebug() <<json;

}

---

module2 header file

#include<QProgressDialog>
namespace Ui {
class Module2;
}

class Module2 : public QWidget
{
    Q_OBJECT

public:
    explicit Module2(QWidget *parent = nullptr);
    ~Module2();
 
    loaddepth *fileData1;

private slots:
    void onReadStatusChanged(int,QString,QString,double);
    void onReadFileCompleted(int,QJsonObject);
};

---

Thread header file

#include<QtCore>
class loaddepth:public QThread
{
   Q_OBJECT
public:
    loaddepth(QObject *parent=0);
    void run() override;
    bool stop;
   QString  filename; int day_no;
   int deepth_no;
      QJsonObject obj;
int file_no;

signals:

        void readStatusChanged(int,QString,QString,double);
        void ReadFileCompleted(int,QJsonObject);

 
};

[Christian Ehrlicher]

This is working fine for me:

#include <QtCore>

class MyThread : public QThread
{
  Q_OBJECT
public:
  using QThread::QThread;

  void run() override
  {
    while (true) {
      emit emitSignal();
      QThread::sleep(2);
    }
  }

Q_SIGNALS:
  void emitSignal();
};

class MyObject : public QObject
{
  Q_OBJECT
public:
  MyObject(QObject *parent = nullptr)
    : QObject(parent)
  {
    MyThread *mt = new MyThread(this);
    connect(mt, &MyThread::emitSignal, this, &MyObject::mySlot);
    mt->start();
  }
private Q_SLOTS:
  void mySlot() { qDebug() << "Got signal!"; }
};

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

    MyObject obj;
    return app.exec();
}

#include "main.moc"

Btw: no need to create (and leak) a QFile object on the heap.