Need a little help with QPushButton & connect

mrmorph

I have just started working on a plugin for the program Daz Studio and I'm stuck on what I thought would be a simple process to get an event when a button is pressed. Alas that it does not work.

So I have in my main .cpp :

QPushButton* button1 = new QPushButton(tr("Button 1"));
mainLyt->addWidget(button1);
connect(button1, SIGNAL(clicked()), this, SLOT (doSomething()));

Then a function :

void DzSceneInfoPane::doSomething()
{
	QMessageBox* box = new QMessageBox();
	box->setWindowTitle("Hello");
	box->setText("You clicked !");
	box->show();		
}

And in my header files :

public slots:
	void			doSomething();

Apologies if my terminology is off, I'm new to C++.

Could anyone help ?

Also there does not seem to be a way to format code in this message.

SGaist

Hi and welcome to devnet,

For Signals and Slots to work you need an event loop running, usually through the call of QApplication's exec function. Do you have that ?

Yes there is, the forum uses Markdown, you can surround your code with three back ticks (three back ticks, new line(s) with code and again three back ticks after a new line after your last code line)

mrmorph

Hello there !

Thanks for your reply.

I edited my message, thanks for the tip.

Currently I am just playing with some examples so I am inserting code to see what it does layout-wise. Then later I can start proper.

I don't at this stage know how to get a loop running, but I will look into it.

SGaist

The shortest way to get started is to create a new widget project and you'll have everything you need.

mrmorph

Does my code above look right ?

In this code I am playing with there are already SIGNALS and SLOTS being used.

I'm just wondering if my code above is okay.

After spending a few hours trying to get one button to work I'm losing the will to live ;)

JKSH

@mrmorph said:

Does my code above look right ?

In this code I am playing with there are already SIGNALS and SLOTS being used.

I'm just wondering if my code above is okay.

Unfortunately, you haven't posted enough code for us to tell if your code is right or not.

Without seeing your code, my advice is:

Make sure your DzSceneInfoPane header contains the Q_OBJECT macro. If you don't, you can't define your own signals or slots.
Always pay attention to error and warning messages that you get. They contain valuable information about what's wrong.

After spending a few hours trying to get one button to work I'm losing the will to live ;)

I suggest following these tutorials. They are extremely simple, and use QPushButton:

https://doc.qt.io/archives/4.3/tutorial-t1.html -- This just makes a QPushButton that does nothing
https://doc.qt.io/archives/4.3/tutorial-t2.html -- This shows you how to connect a QPushButton to another class's slot

At the botton of Tutorial 1, it says "If you have typed in the source code manually, you will need to follow these instructions"... ignore that part.

mrmorph

Yes thank you, I think you are both right. I will have to start from fresh and learn step by step.

Thanks to you both for helping, I appreciate it :)

jsulm

You have a memory leak in:

void DzSceneInfoPane::doSomething()
{
    QMessageBox* box = new QMessageBox();
    box->setWindowTitle("Hello");
    box->setText("You clicked !");
    box->show();        
}

You never delete box.

mrmorph

I started fresh and am getting there in other areas, but this darned button is still a problem.

In the examples you kindly posted there is this :

#include <QApplication>
 #include <QPushButton>

 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);

     QPushButton hello("Hello world!");
     hello.resize(100, 30);

     hello.show();
     return app.exec();
 }

Which is fine, but the examples I am working from do not use main. Other wise I have set things up as suggested, but I get nada. Here's my code... edit the forum formatting does not seem to work today.

CPP :

#include "myfirstplugin.h"

#include <QtCore/QObject>
#include <QtGui/QPushButton>
#include <QtGui/QVBoxLayout>

#include "dzapp.h"
#include "dzbone.h"
#include "dzfacetmesh.h"
#include "dzhelpmgr.h"
#include "dzobject.h"
#include "dzscene.h"
#include "dzshape.h"
#include "dzskeleton.h"
#include "dzstyle.h"

#include "dzplugin.h"



myFirstPlugin::myFirstPlugin() : DzPane("Hello there") {

	QGroupBox *groupBox = new QGroupBox(tr("Exclusive Radio Buttons"));

	QRadioButton *radio1 = new QRadioButton(tr("&Radio button 1"));
	QRadioButton *radio2 = new QRadioButton(tr("R&adio button 2"));
	QRadioButton *radio3 = new QRadioButton(tr("Ra&dio button 3"));

	radio1->setChecked(true);

	QGridLayout *gLay = new QGridLayout(groupBox);

	gLay->addWidget(radio1);
	gLay->addWidget(radio2);
	gLay->addWidget(radio3);

    //Create QPushButton
	QPushButton *button1 = new QPushButton(tr("Button 1"));
	button1->setObjectName("button1");

    QMetaObject::connectSlotsByName(this);

	// Define the layout for the pane
	QVBoxLayout *mainLyt = new QVBoxLayout();
	mainLyt->addWidget(groupBox);
	mainLyt->addWidget(button1);
	mainLyt->addStretch(1);

	// Set the layout for the pane
	setLayout(mainLyt);

    showPane();

	connect(button1, SIGNAL(pressed()), this, SLOT(doThis()));
}


myFirstPlugin::~myFirstPlugin(){

}


void myFirstPlugin::doThis() {

	QMessageBox* box = new QMessageBox();
	box->setWindowTitle("Hello");
	box->setText("You clicked !");
	box->show();
}

And my header :

#ifndef MYFIRSTPLUGIN_H
#define MYFIRSTPLUGIN_H

#include "dzpane.h"
#include "dzaction.h"
#include <QtGui/QPushButton>

class myFirstPluginAction : public DzPaneAction {
    Q_OBJECT
public:
    myFirstPluginAction() : DzPaneAction("myFirstPlugin") {
    }
};

class myFirstPlugin : public DzPane {
    Q_OBJECT
public:
    myFirstPlugin();
    ~myFirstPlugin();

public slots:
	void			doThis();

private:
	QPushButton		*button1;

};



#endif // MYFIRSTPLUGIN_H

[edit: fixed coding tags, three back-ticks SGaist]

mrjj

hi
If you don't have a main then you most likely don't have

int main(int argc, char *argv[])
{
QApplication app(argc, argv);
return app.exec();
}

the app.exec() is an event loop and it makes signals and slot works.
So if its not running then no "click" will
ever work.

So it seem you are trying to make plugin for another program.
Does this program expect it to be a DLL ?
Are the samples you are using, for building a plugin with qt?

when there is no main, then no much will happen when you run it.

mrmorph

No I don't have that.

But the samples I was working from are using SLOTS and SIGNALS without it.

It's a plugin yes - it's for Daz Studio, a graphics program.

It uses DLLs yes. I can successfully build the DLL and it loads and will show my widgets within the main program.

But whatever I try I can't get it to detect when I click on the button.

Maybe there is a library I am missing, but as far as I can tell I'm using all the same includes as the examples that have the working events.

mrjj

@mrmorph
Ok so the examples are for Qt ?
And all loads in Daz Studio and you can see the button etc?
I assume this
connect(button1, SIGNAL(pressed()), this, SLOT(doThis()));
is the button in question ?
try output if connect is ok.
bool status = connect(button1, SIGNAL(pressed()), this, SLOT(doThis()));
if (!status)
QMessageBox...

to see if the actual connect that fails

Do you have a link for the examples ?
Must be something simple missing.

mrmorph

Hi, thanks for trying to help.

And sorry yes, the samples are for Daz Studio yes and they work fine.

Everything loads yes and I can see the radio buttons and button - they are in a window... as in this snip...

Image to show it working in the main program...

button1 is the one I am trying to get to work yes.

I inserted this as suggested.

bool status = connect(button1, SIGNAL(pressed()), this, SLOT(doThis()));

	if (status) {
		QMessageBox* box = new QMessageBox();
		box->setWindowTitle("Hello");
		box->setText("Works");
		box->show();
	}
	else {
		QMessageBox* box = new QMessageBox();
		box->setWindowTitle("Hello");
		box->setText("Does not work");
		box->show();
	}

The connect appears to fail as I get 'Does not work'.

Thanks for formatting my previous code properly, I got the wrong key.

EDIT Opps, you wanted the samples. They are free here, but you would need to register. I don't think I can distribute the files myself.

http://www.daz3d.com/daz-studio-4-5-sdk

mrjj

@mrmorph said:
Hmm, one note

QPushButton *button1 = new QPushButton(tr("Button 1"));
you make new one but in .h you have one in class myFirstPlugin

so should it be
button1 = new QPushButton(tr("Button 1")); ?

also, since it fails, (the connect) we need to find out why

could you try the new syntax as it catch stuff compile time

connect(button1, &QPushButton::released, this, &myFirstPlugin::doThis);

mrmorph

Tried

button1 = new QPushButton(tr("Button 1"));

But still the same, does not work.

mrjj

@mrmorph
well was just a note. the real issues is why connect fails.
can you try the new syntax
connect(button1, &QPushButton::released, this, &myFirstPlugin::doThis);

mrmorph

Visual Studio does not like that.

For connect there is a 'no instance of overload function "myFirstPlugin::connect" matches the argument list......'

And &QPushButton::released is inaccessible...

BTW, I am using Qt 4.8.1 as that's what Daz Studio is using.

Sorry about the slow replies, it's not letting me post as I am a noob. Some 500 second limit.

mrjj

@mrmorph
oh. sorry. thought it was 5.0+
forget new syntax then.

since connect fails , there must be something wrong.
but all seems fine.
doThis is public slot. buttons1 is allocated.
just so I 100% sure , can u try the released signal instead?
connect(button1, SIGNAL(released()), this, SLOT(doThis()));
and see if still say "not works"

np. its spam protection but is indeed annoying sometimes.
ps. QMessageBox* box = new QMessageBox();
need a delete box; else its a leak but ok for now.

mrmorph

No problem, I should have mentioned I was on an older Qt.

Same thing with released().

Thanks for the tip about the MessagBox delete, someone else did mention it, but it was always just a temporary thing.

I wonder if I have to hook into something else that's in Daz Studio.

Just as an example, the sample I am working from as reference uses connect like this :

connect( dzScene, SIGNAL(sceneLoadStarting()), this, SLOT(blockRefresh()) );

Now it also has this include :

#include "dzscene.h"

The scene would be the main graphics window and other things. Perhaps there is some loop being started in there because it uses dzScene in the connect, not a widget or anything like I am using.

Maybe I need to include another library to get the loop for the widgets.

Just grabbing at straws.

mrjj

@mrmorph said:

connect( dzScene, SIGNAL(sceneLoadStarting()), this, SLOT(blockRefresh()) );

On the signal sceneLoadStarting call blockRefresh
so that is very like button.
Do you have access to a dzScene instance? Like the default scene ?
you could try to hook it up with your doThis and then load new scene or what ever
that signal means.

Whole SDK seems to be build with Qt so might have global event loop for plugins.
So I doubt you need anything else since it loads DLL.

But I don't like that connect fails. as even no event loop, the connect should not fail
as far as I know .
But syntax seems fine. so I wonder.

When you click on button, it does animate ? Meaning show being pressed ?

Also the default examples do work? I assume they use some gui too?

also, could you move connect over "showpane"
I assume pane shows then it says "not work" while pane is shown?