QDialog don't show widgets, when method show() calling

Pradeep Kumar

hi,

And u said u need to get the dialog on perform of some task, can u specify the situation ?. when u need and based on that, u can call the dialog in slot.

Thanks,

oBOXPOH

Comrades! What I have got:

WaitingDialog dlg(this); //this - some custom widget
dlg.show();

// some code (without other dialogs)

I delete dlg.close(), but there is changed nothing.

WaitingDialog dlg = new WaitongDialog;
dlg->show();

// some code

I create dialog without parent and just show this dialog. In the beginning of execution (when Qt calls dialog) I see the dialog only with title, but when the execution of some code finished (I'm not close dlg (dlg->close()), the content of the dialog became visible.

In code I don't call to dialogs, just compute some values.

Strangely!

oBOXPOH

@SGaist said in QDialog don't show widgets, when method show() calling:

Hi,

Can you show the complete method code where you create that dialog ?

Code of the dialog:

WaitingDialog::WaitingDialog(QWidget *parent) :
    QDialog(parent, Qt::CustomizeWindowHint | Qt::WindowTitleHint)
{
    mainLayout = new QHBoxLayout;

    textLabel = new QLabel(tr("Processing..."));
    mainLayout->addWidget(textLabel);

    setLayout(mainLayout);

    setWindowTitle(tr("Waiting"));
}

WaitingDialog::~WaitingDialog(){}

Code of the method:

{
    ...

    WaitingDialog *dlg = new WaitingDialog;
    dlg->show();
    Sleep(10000);
}

In the beginning the dialog show only title. After 10 seconds I get management of parent (where I use this code) and content of the dialog (QLabel) in this dialog. I.e. get content only after Sleep!

Vinod Kuntoji

@oBOXPOH ,

What are you executing?

oBOXPOH

@Vinod-Kuntoji said in QDialog don't show widgets, when method show() calling:

@oBOXPOH ,

What are you executing?

Code of the method:

{
    ...

    WaitingDialog *dlg = new WaitingDialog;
    dlg->show();
    Sleep(10000);
}

Devopia53

@oBOXPOH

Never use the Sleep(). This is because the currently executing thread(aka. GUI) is blocking.

like this:

WaitingDialog *dlg = new WaitingDialog(this);
QTimer::singleShot(10000, [=, dlg]{ 
    /* Manage what you want here. */
    dlg->deleteLater(); 
});
dlg->setModal(true);
dlg->show();

Vinod Kuntoji

@oBOXPOH ,

Are you showing dialog inside thread?

oBOXPOH

I used Sleep() as example. If instead of Sleep() I want compute something during showing dialog, what can I do?

SGaist

Except that you will block the main thread and thus your dialog will not show until its too late.

If you have a long computational process running you should consider maybe using QtConcurrent and wire that properly with your GUI.

oBOXPOH

@Vinod-Kuntoji said in QDialog don't show widgets, when method show() calling:

@oBOXPOH ,

Are you showing dialog inside thread?

I show dialog, when something button was clicked. During this dialog some computing task must execute. When this task finish, this dialog must close.

Vinod Kuntoji

@oBOXPOH ,

Are you talking about progressbar?

oBOXPOH

@Vinod-Kuntoji said in QDialog don't show widgets, when method show() calling:

@oBOXPOH ,

Are you talking about progressbar?

Just about some dialog with text without any buttons. If it easier for you, yes, about progressbar.

mrjj

Hi

Just about some dialog with text without any buttons. If it easier for you, yes, about progressbar.

Its not so much about being easier.
Its a concrete class
http://doc.qt.io/qt-5/qprogressbar.html

Also
WaitingDialog *dlg = new WaitingDialog;
dlg->show();
Sleep(10000); <<< here u lag all of application. nothing can be drawn and u will first see dialog after 10 secs.

Sleep cannot be used to simulate a workload.

oBOXPOH

@mrjj said in QDialog don't show widgets, when method show() calling:

Hi

Just about some dialog with text without any buttons. If it easier for you, yes, about progressbar.

Its not so much about being easier.
Its a concrete class
http://doc.qt.io/qt-5/qprogressbar.html

Also
WaitingDialog *dlg = new WaitingDialog;
dlg->show();
Sleep(10000); <<< here u lag all of application. nothing can be drawn and u will first see dialog after 10 secs.

Sleep cannot be used to simulate a workload.

I know! I wrote Sleep() only for example. But even in this case dlg->show() doesn't show content of the dialog, shows only title and window.

mrjj

@oBOXPOH

Ok, but you description of your issue , sounds 100% when a poster loop/sleep the main thread and
other windows shows up as empty becuase there is no time to draw the child widgets.

dlg->show() doesn't show content of the dialog, shows only title and window.

Well do you call a loop or something else after you open the dialog ?

Clearly
WaitingDialog *dlg = new WaitingDialog;
dlg->show();

must work and i assume the widget IN the dialog is made with UI file so all should be ok ?

There is something you are not telling :)

Vinod Kuntoji

@oBOXPOH ,

WaitingDialog *dlg = new WaitingDialog;
dlg->exec();

connect(dlg,SIGNAL(aborted()),dlg,SLOT(stopDialog()));
connect(yourWidget,SIGNAL(executionComplete()),dlg,SLOT(stopDialog()));

void WaitingDialog::stopDialog() {
this->close();
emit aborted();
}

oBOXPOH

@Vinod-Kuntoji said in QDialog don't show widgets, when method show() calling:

@oBOXPOH ,

WaitingDialog *dlg = new WaitingDialog;
dlg->exec();

connect(dlg,SIGNAL(aborted()),dlg,SLOT(stopDialog()));
connect(yourWidget,SIGNAL(executionComplete()),dlg,SLOT(stopDialog()));

void WaitingDialog::stopDialog() {
this->close();
emit aborted();
}

It seems logical. I'll try. Thanks!

VRonin

I'll say what everybody else is afraid to say. Because this is not the solution Gotham deserves but it's the one it needs right now:
just add QApplication::processEvents(); after dlg.show();

mrjj

@VRonin
hehe first time i seen the evil QApplication::processEvents() served with a batman quote :))

oBOXPOH

@VRonin said in QDialog don't show widgets, when method show() calling:

I'll say what everybody else is afraid to say. Because this is not the solution Gotham deserves but it's the one it need right now:
just add QApplication::processEvents(); after dlg.show();

It's working! Thanks a lot! Great!