create a Class inherits from two QObject subclasses

Hi,

How can I create a Class inherits from two QObject subclasses in Qt 4.3 ?

Eg:

Code:

---

class MyClass:: public Class1 , protected QThread 
{
   .......
}

---

Please help me.

It is not possible to inherit from 2 QObject classes. Instead inherit only the first one and make your class to be a wrapper around QThread - it doesn't have that many methods anyway. Create a QThread member and expose its API through your class.

EDIT: look at this... eclipse even tells you you can't inherit from two QObject's:

Hi,
I am not very clear with your answer. Can you please give an sample code for it ?

Hi,
How can I solve this problem?
Please help me

Code:

---

class MyClass : public Class1
{
Q_OBJECT
 
protected:
 MyThread *mThread;
 
public:
 MyClass(QObject* = NULL);
 ~MyClass();
 
  //expose QThread API
  void start() {
   mThread->start();
  } 
  .. you can add other QThread methods and slots here
}

---

Here MyThread is a QThread subclass.

Hi,
When I try this, at the time of running the program, Qt display an error like this

Quote:

---

First-chance exception at 0x67015e8a (QtCored4.dll) in Test.exe: 0xC0000005: Access violation reading location 0xcdcdcdd1.
Unhandled exception at 0x67015e8a (QtCored4.dll) in Test.exe: 0xC0000005: Access violation reading location 0xcdcdcdd1.

---

Please help me to solve this problem.

You're dereferencing an uninitialized pointer. Do you have something like

Code:

---

mThread = new MyThread(this);

---

anywhere in your code?

Hi
My code is like this

Code:

---

{
protected:
	QThread *mThread;
       ........
 
public:
    void start() {
		mThread->start();
	} 
	virtual void run();
 
}

---

and in my .cpp file the code is like this

Code:

---

void CTest::StartCapture (int DeviceNum ){
 
	capture = cvCaptureFromCAM( DeviceNum );
 
	if( !capture ) {
		 fprintf( stderr, "ERROR: capture is NULL \n" );
		 getchar();
	}
	mThread->start();
 
}
 
 
void CWebCamViewer::run() {
 
	while( true ) {
		// Get one frame
		qApp->processEvents();
				ImgFrame = cvQueryFrame( capture );
				if( !ImgFrame ) {
					fprintf( stderr, "ERROR: frame is null...\n" );
					getchar();
					break;
				}
				ReturnImg = IplImageToQImage(ImgFrame);
				hflip =  ReturnImg->transformed(QMatrix().scale(1,-1));
				hflip = hflip.scaled(320,240, Qt::IgnoreAspectRatio, Qt::FastTransformation);
				Picture->setPixmap(QPixmap::fromImage(hflip));
		}
}

---

Please help me to solve that problum.

Could you answer my question?

Hi,
No, I didn't give a line like this

Code:

---

mThread = new MyThread(this);

---

in my program

So most likely mThread is an uninitialized pointer which points to 0xcdcdcdd1. Don't you think you should have

Code:

---

mThread = new QThread(this);

---

somewhere?

Hi
When I give the command in my constructor

Code:

---

mThread = new QThread(this);

---

then Qt return an error like this

Quote:

---

.\Test.cpp(70) : error C2259: 'QThread' : cannot instantiate abstract class
due to following members:
'void QThread::run(void)' : is abstract
c:\qt\4.3.0\include\qtcore\qthread.h(87) : see declaration of 'QThread::run'

---

Ahh, indeed. QThread will be non-abstract in Qt 4.4 but until that you will have to implement QThread::run().

Hi,
In my code I had implement the run(). Please see the code , which one i previous declare.

in .h file

Code:

---

virtual void run();

---

and in .cpp file

Code:

---

void CTest::run() {
  .....
  .....
 }

---

is it correct?

A friendly advise would be to learn C++ before trying to use a comprehensive toolkit written in C++. Using Qt sure requires some knowledge of C++.

What you have shown above declares a method "virtual void run()" in a class which has QThread pointer as a member. That's not at all same than implementing QThread::run().

Notice the difference between:

Code:

---

class Foo : public QObject
{
protected:
  virtual void run() { ... }
 
  QThread* mThread;
};

---

and

Code:

---

class MyThread : public QThread
{
protected:
  virtual void run() { ... }
};
 
class Bar : public QObject
{
protected:
  MyThread* mThread;
};

---

Hi,
Its my mistake. Sorry.

I create a class like this

Code:

---

class MyThread : public QThread
{
 
  protected:
	  virtual void run(){
		  while(true){
		  qDebug()<<"Run";
                   } 
	  }
 
};

---

and in .h file

Code:

---

QThread *mThread;

---

and give the command in my constructor like this

Code:

---

mThread = new QThread(this);

---

but the error is like this

Code:

---

.\Test.cpp(70) : error C2259: 'QThread' : cannot instantiate abstract class
        due to following members:
        'void QThread::run(void)' : is abstract
        c:\qt\4.3.0\include\qtcore\qthread.h(87) : see declaration of 'QThread::run'

---

Please help me

QThread is abstract. You must instantiate your QThread subclass:

Code:

---

mThread = new MyThread(this);

---

Hi,
Ohhhh, It's my mistake. Sorry.
Thankyou for your help