QThread Data Access Method

Hi all:

Just got a basic question concerning QThread. Say if my QThread Object is inside another inherited QMainwindow which also contains other non-Qt classes. If i start a the thread, what should i do to make the run() function of QThread to have access to the members in the calling inherited QMainwindow class? Thanks in advance!

schan117

call a public fuction in the thread class
ex:

Code:

---

public:
    void startThread();
     void run();
 
in void startThread() 
 {
       if(!isRunning()){
                start();
        }
}

---

so in the mainwindow class call
thread->startThread();

and it will automatically call the run() of the thread()

pass the thread's constructor a pointer to the data you want to access.
Make sure you guard (i.e. lock) against read/write conflicts when accessing the same data in different threads. Also note that QWidgets may only be accessed from the gui thread.

Quote:

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Originally Posted by schan117

If i start a the thread, what should i do to make the run() function of QThread to have access to the members in the calling inherited QMainwindow class? Thanks in advance!

---

You shouldn't do that because widget classes are not thread safe.

Hi all:

Thanks for the answers guys. So this means I can only pass to the thread a QWidget class but not some other classes? I am asking this because I want to QThread to access to the camera object of parent class to do capturing and display it on QLabel. Another way I think of is to use QTimer. Whats your ideas guys? Thanks!

schan117

No, QWidget is not thread-safe as well. You musn't call any of QWidget (or descendant) methods from within a worker thread. If you want to transfer data between the worker thread and the main thread, you have to use either events or signals.

So you mean what i should do is to setup the thread to emit a signal when inside run() of the QThread Class and connect it back to a slot of the parent class and from that access the data?

schan117

follow this example ... it suits exact requirement for u on QThread
http://doc.trolltech.com/4.0/network...uneclient.html