QThread locks my gui ??

[LordQt]

Hello friends,

When I click my Gui B button it starts a QThread.

class CheckFile : public QThread
//**************************************************************************
{
	Q_OBJECT
	public:
		CheckFile(const QString &p_inFile,
                    const QString &p_notInsertedFile,
                    QObject* parent = 0);
		virtual ~CheckFile() { }
	public slots:
	protected:
        void run();
    private:
        QString qstr_inFile;
        QString qstr_notInsertedFile;
	private slots:
	signals:
 
        void setText(const QString &);
 
};

class CheckFile : public QThread
//**************************************************************************
{
	Q_OBJECT
	public:
		CheckFile(const QString &p_inFile,
                    const QString &p_notInsertedFile,
                    QObject* parent = 0);
		virtual ~CheckFile() { }
	public slots:
	protected:
        void run();
    private:
        QString qstr_inFile;
        QString qstr_notInsertedFile;
	private slots:
	signals:

        void setText(const QString &);

};

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in the implementation I parse a file and emit for every line a settext like this

void CheckFile::run()
{
QString str;
...
emit setText(str);
}

void CheckFile::run()
{
QString str;
...
emit setText(str);
}

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In the Slot function for my button clicked event I declare my connection for the Thread :

connect(thr_CheckFile, SIGNAL(setText(const QString& )), bodyEdit, SLOT(append(const QString&)));

connect(thr_CheckFile, SIGNAL(setText(const QString& )), bodyEdit, SLOT(append(const QString&)));

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after the text are append to my Qtextedit in my gui my window freeze that means I can not do anything and the memory using grows up

Any Suggestions ??

[^NyAw^]

Hi,

How do you start the QThread?

[LordQt]

Like this:

thr_CheckFile = new CheckFile(selectedItemFile,
                                  notInsertedFile,
                                  this);
 
connect(thr_CheckFile, SIGNAL(setText(const QString& )), bodyEdit, SLOT(append(const QString&)));
thr_CheckFile->start();

thr_CheckFile = new CheckFile(selectedItemFile,
                                  notInsertedFile,
                                  this);

connect(thr_CheckFile, SIGNAL(setText(const QString& )), bodyEdit, SLOT(append(const QString&)));
thr_CheckFile->start();

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[^NyAw^]

Hi,

Maybe the SLOT "append" is reciving too much data every time the SIGNAL is emmited.
Try using a QString variable and append the data into it. When the QThread finish you can set the text to the QTextEdit.

[LordQt]

Hmm I think I am not sure if I understand you.

I use a QString as parameter.... ?????

[^NyAw^]

Hi,

connect(thr_CheckFile, SIGNAL(setText(const QString&)), this, SLOT(appendString(const QString&)));
 
//Connect the Thread Finished signal
connect(thr_CheckFile, SIGNAL(finished()),this,SLOT(threadFinished())));
 
...
void yourClass::appendString(const QString& qString)
{
  //QString m_qString;  //Declared on yourClass
  m_qString.append(qString);
}
void yourClass::threadFinished()
{
  //When the Thread is finished we have all the data that want to show to QTextEdit
  bodyEdit.setText(m_qString);
}

connect(thr_CheckFile, SIGNAL(setText(const QString&)), this, SLOT(appendString(const QString&)));

//Connect the Thread Finished signal
connect(thr_CheckFile, SIGNAL(finished()),this,SLOT(threadFinished())));

...
void yourClass::appendString(const QString& qString)
{
  //QString m_qString;  //Declared on yourClass
  m_qString.append(qString);
}
void yourClass::threadFinished()
{
  //When the Thread is finished we have all the data that want to show to QTextEdit
  bodyEdit.setText(m_qString);
}

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Something like this maybe will help you.

[LordQt]

Ok thank you....

but I think I have to implement a Progressbar for big files ... ;O)))

[nix]

Hi,

I'm not an expert in Qt multi-threading but I think your problem comes from your connect() parameters. You try to send a signal from one thread to the gui's one, this can be dangerous if you don't take care of it.

When you send a signal from a thread to an other, try to use something like this :

connect(thr_CheckFile, SIGNAL(setText(const QString&)), this, SLOT(appendString(const QString&)), Qt::QueuedConnection);

connect(thr_CheckFile, SIGNAL(setText(const QString&)), this, SLOT(appendString(const QString&)), Qt::QueuedConnection);

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This will post the signal in the signal queue of the gui thread, and then, thread will manage it later as any other event from the GUI.

I already had the same problem as you, where a thread sends some signals to the gui in order to make a progress bar raise, with the Qt::QueuedConnection it's works fine. A piece of advice : I had some stange troubles with the connect() function when I used it in a thread, now I always specify the fifth parameters in this case (even if the default should work) and I don't have any surprises anymore.

I hope it can solve the locks of your GUI.

[wysota]

You don't need to use any threads here, use QProgressDialog or something similar.