[Qt-interest] the problem of QProgressDialog & QProgressBar

[John McClurkin]

John McClurkin wrote:
> Malyushytsky, Alex wrote:
>>  >> But the progress dialogue only shows after( or at the same time) 
>> THE SysInfo Dialogue.
>>  >> WHY??
>>
>> Because of    p_ShowSysInfoDlg->exec(); I guess.
>>
>> I don’t think event loop of application is running when you open 
>> another modal dialog.
>>
>>  
>>
>> Regards,
>>
>>     Alex
>>
>>  
>>
>> * *
>>
>> * *
>>
>> *From:* qt-interest-bounces at trolltech.com 
>> [mailto:qt-interest-bounces at trolltech.com] *On Behalf Of *Gan Xiebin
>> *Sent:* Monday, July 13, 2009 11:01 PM
>> *To:* qt-interest
>> *Subject:* Re: [Qt-interest] the problem of QProgressDialog & 
>> QProgressBar
>>
>>  
>>
>> Hi Alex,
>>
>> Thanks for reply.
>> I have a code like that,
>>
>> ----------------------
>> void MainWindow::SysInfoFunc()
>> {
>>     SysInfoDlg *p_ShowSysInfoDlg = new SysInfoDlg( );
>>     p_ShowSysInfoDlg->exec();
>> }
>>
>> SysInfoDlg::SysInfoDlg(QWidget *parent)
>>     : QDialog( parent )
>> {
>>   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( ... );
>>  
>> }
>> ------------------------------------
>>
>>
>> I must ensure that the application does not freeze.
>> I read the document carefully, and used QProgressDialog ...
>>
>> ---------------------------------------------
>> void MainWindow::SysInfoFunc()
>> {
>>
>>     progressDlg = new QProgressDialog("Operation in progress.", 
>> "Cancel", 0, 100, this);
>>     connect(progressDlg, SIGNAL(canceled()), this, 
>> SLOT(cancelProgressDlg()));
>>     timer = new QTimer(this);
>>     connect(timer, SIGNAL(timeout()), this, SLOT(performProgressDlg()));
>>     timer->start(0);
>>
>>     progressDlg->setValue(0);
>>        SysInfoDlg *p_ShowSysInfoDlg = new SysInfoDlg(node);
>>     p_ShowSysInfoDlg->exec();
>>
>>     progressDlg->setValue(progressDlg->maximum());
>>
>> }
>>
>> void MainWindow::cancelProgressDlg()
>> {
>>     timer->stop();
>>     progressDlg->close();
>> }
>>
>> void MainWindow::performProgressDlg()
>> {
>>     if(progressDlg->value() + 1 < progressDlg->maximum())
>>     {
>>         progressDlg->setValue(progressDlg->value() + 1);
>>     }
>>     else
>>     {
>>         timer->stop();
>>         progressDlg->close();
>>     }
>>
>>     qApp->processEvents();   }
>> --------------------------------
>>
>>
>> But the progress dialogue only shows after( or at the same time) THE 
>> SysInfo Dialogue.
>> WHY??
>>
>> P.S. : I used the model dialogue of QProgressDialog, but have no 
>> effect for me.
>>
>> Thanks.
> 
> 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.