[Qt-interest] the problem of QProgressDialog & QProgressBar

[John McClurkin]

Gan Xiebin wrote:
> Malyushytsky, Alex wrote:
>  > Because of    p_ShowSysInfoDlg->exec(); I guess.
>  >
>  > I don’t think event loop of application is running when you open another
>  > modal dialog.
>  >
> 
> John McClurkin wrote:
>  > Alex is correct. calling p_ShowSysInfoDialog->exec() blocks the
>  > application until it returns. If you want the progress dialog to show
>  > progress during the execution of the SysInfoDialog, create the progress
>  > dialog first on the heap and pass a pointer to the SysInfoDialog
>  > constructor. Then, in the SysInfoDialog exec function, update the
>  > progress dialog periodically and call QApplication::processEvents().
> 
>  > I forgot to add that you show() the progress dialog in the SysInfoDialog.
> 
> 
> Thanks Alex and John.
> 
> OK. The exec() blocks the application until it returns.
> But although I create the progress dialogue and pass a pointer to the 
> SysInfoDialog constructor,
> the GUI thread still blocks while I used wait() in the event loop, right ?
> What should I do ?
> Any reply is welcome. Thanks.
The worker threads will block, but the GUI thread should not. If all of 
the time is spent in the worker threads, you can have them send signals 
at intervals and connect those signals to slots in SysInfoDlg which will 
then update the progress bar.

> 
> -------------------------------------------------
> void MainWindow::SysInfoFunc()
> {
> 
>     progressDlg = new QProgressDialog("Operation in progress.", 
> "Cancel", 0, 100, this);
>    
>     SysInfoDlg *p_ShowSysInfoDlg = new SysInfoDlg(node, progressDlg);
>     p_ShowSysInfoDlg->exec();
> 
> }
> 
> ysInfoDlg::SysInfoDlg(Node *node, QProgressDialog *progressDlg, QWidget 
> *parent)
>     : QDialog( parent )
> {
>     this->progressDlg = progressDlg;
>     this->progressDlg->setValue(0);
> 
>     timer = new QTimer(this);
>     connect(timer, SIGNAL(timeout()), this, SLOT(performProgressDlg()));
>     timer->start(1000);
> 
>     this->progressDlg->show();
>     QApplication::processEvents();
> 
> // set text
>   textLabel = new QLabel();
> 
>   thread1.start();  // A task
>   thread2.start();  // Another task
> 
>   thread1.wait(); // wait for task finished, and set text to the label
>   thread2.wait(); // like thread1 ...
> 
>   textLabel->setText( ... );
> 
> // close dialog
>     timer->stop();
>     this->progressDlg->close();
> }
> 
> void SysInfoDlg::performProgressDlg()
> {
>     if(progressDlg->value() + 1 < progressDlg->maximum())
>     {
>         progressDlg->setValue(progressDlg->value() + 1);
>     }
>     else
>     {
>         timer->stop();
>         progressDlg->close();
>     }
>     progressDlg->show();
>     QApplication::processEvents();
> }
> 
> --------------------------------------------------------------------------------------