Parent and Child Window Communication

[Harini]

As i'm trying to create a connection b/w parent and child window facing a problem with the following errors & warnings


/home/stesalit/Desktop/tasks/multi-windw-back/info.cpp:8: error: invalid use of incomplete type ‘struct Ui::Info’
/home/stesalit/Desktop/tasks/multi-windw-back/info.h:7: error: forward declaration of ‘struct Ui::Info’

/home/stesalit/Desktop/tasks/multi-windw-back/info.cpp:14: warning: possible problem detected in invocation of delete operator:


Here are my .h and .cpp files in attachments.Can any one please help me in sorting out the issue????

[anda_skoa]

Ui::Info should have been define in ui_info.h

This is a generated file, its source file should be info.ui
Check that the form declared in it is called Info.

Btw, posting screenshots of code is suboptimal. either attach the project as a ZIP or post the code in code tags

Oh and it helps if a thread's subject is actually about the problem :-)

Cheers,
_

[Harini]

Thanks a lot for ur suggestion AS I'm new to Qt,I dont know how to define Ui::Info in ui_info.h can u please explain me...

[anda_skoa]

I assume you have created the files using "New File" and selected "Designer Form Class".
That will usually generate the files and proper names.

My guess is that you have a Form file called info.ui but that you have changed the name of the top level item in it.
If so you can either change it back to "Info" or change the usage of "Info" in info.h and info.cpp to whatever name you have now chosen.

Cheers,
_

[Harini]

Thank you sir @ anda_skoa

But here I'm getting only parent window am not getting any child.There is no communication b/w parent and child. Here is my code can please suggest me anything

#ifndef INFO_H
#define INFO_H
 
#include <QMainWindow>
 
namespace Ui {
    class info;
}
 
class info : public QMainWindow {
    Q_OBJECT
public:
    info(QWidget *parent = 0);
    ~info();
 
protected:
    void changeEvent(QEvent *e);
 
private:
    Ui::info *ui;
};
 
 
#endif // INFO_H

#ifndef INFO_H
#define INFO_H

#include <QMainWindow>

namespace Ui {
    class info;
}

class info : public QMainWindow {
    Q_OBJECT
public:
    info(QWidget *parent = 0);
    ~info();

protected:
    void changeEvent(QEvent *e);

private:
    Ui::info *ui;
};


#endif // INFO_H

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#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include <info.h>
#include <QtGui>
 
namespace Ui {
    class MainWindow;
}
 
class MainWindow : public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
 
protected:
    void changeEvent(QEvent *e);
 
private:
    Ui::MainWindow *ui;
    void setSignals();
     void process();
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <info.h>
#include <QtGui>

namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();

protected:
    void changeEvent(QEvent *e);

private:
    Ui::MainWindow *ui;
    void setSignals();
     void process();
};

#endif // MAINWINDOW_H

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#include <QtGui/QApplication>
#include "info.h"
#include "ui_info.h"
 
info::info(QWidget *parent) :
    QMainWindow(parent)
    //ui(new Ui::info)
{
    ui->setupUi(this);
}
 
info::~info()
{
    delete ui;
}
 
void info::changeEvent(QEvent *e)
{
    QMainWindow::changeEvent(e);
    switch (e->type()) {
    case QEvent::LanguageChange:
        ui->retranslateUi(this);
        break;
    default:
        break;
    }
}

#include <QtGui/QApplication>
#include "info.h"
#include "ui_info.h"

info::info(QWidget *parent) :
    QMainWindow(parent)
    //ui(new Ui::info)
{
    ui->setupUi(this);
}

info::~info()
{
    delete ui;
}

void info::changeEvent(QEvent *e)
{
    QMainWindow::changeEvent(e);
    switch (e->type()) {
    case QEvent::LanguageChange:
        ui->retranslateUi(this);
        break;
    default:
        break;
    }
}

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#include <QtGui/QApplication>
#include "mainwindow.h"
#include "info.h"
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

#include <QtGui/QApplication>
#include "mainwindow.h"
#include "info.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

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#include "mainwindow.h"
#include "ui_mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
     setSignals();
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::changeEvent(QEvent *e)
{
    QMainWindow::changeEvent(e);
    switch (e->type()) {
    case QEvent::LanguageChange:
        ui->retranslateUi(this);
        break;
    default:
        break;
    }
}
void MainWindow::setSignals(){
    connect(ui->next,SIGNAL(clicked()),this,SLOT(process()));
    //connect(ui->close,SIGNAL(clicked()),this,SLOT(close()));
}
 
void MainWindow::process(){
        info *i;
        i = new info;
        this -> hide();
        i -> show();
}

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
     setSignals();
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::changeEvent(QEvent *e)
{
    QMainWindow::changeEvent(e);
    switch (e->type()) {
    case QEvent::LanguageChange:
        ui->retranslateUi(this);
        break;
    default:
        break;
    }
}
void MainWindow::setSignals(){
    connect(ui->next,SIGNAL(clicked()),this,SLOT(process()));
    //connect(ui->close,SIGNAL(clicked()),this,SLOT(close()));
}

void MainWindow::process(){
        info *i;
        i = new info;
        this -> hide();
        i -> show();
}

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[anda_skoa]

This probably not compiling (missing include of info.h in the main window source file, and probably crashing because info's source file does not create an instance of the UI class (commented out) but accesses it.

However, MainWindow:rocess() looks right though.

Do you get any runtime warning?

Cheers,
_

[Harini]

@ anda_skoa

Thanks a lot for ur reply


I dint get any error or warning and now I included info.h in main window source file but still facing the same problem.

[Harini]

Hii every one

I want to create a parent and child window. From the parent window i want to call the child window by using signal and slots so here in the ui form i want to customize the slot editor with process().
Here is my signal and slot connection code line which I want to do...

connect(ui->next,SIGNAL(clicked()),this,SLOT(process()));

connect(ui->next,SIGNAL(clicked()),this,SLOT(process()));

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How can i do this?? can any one please help me???

[toufic.dbouk]

You add your intended slot in the header file where the slot will be invoked under public sots.

class nameQueryThread ...
{
 
public:
     nameQueryThread(...);
      ...
signals:
 
public slots:
    void process();
};

class nameQueryThread ...
{
 
public:
     nameQueryThread(...);
      ...
signals:

public slots:
    void process();
};

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From the parent window i want to call the child window by using signal and slots

What do you mean ?
In your slot process create and call the * child window *
in your cpp file

void window::process()
{
// do your code here 
// create and call your child window
}

void window::process()
{
// do your code here 
// create and call your child window
}

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[anda_skoa]

Can you attach the project as ZIP file?

Cheers,
_

[Harini]

@ anda_skoa


yea sure here is my zip file in attachments please solve it

[Harini]

@ toufic.dbouk

Thank you


Here is my project in zip file can u please check it out and suggest me something if i have done any mistake???

[saman_artorious]

You have defined process() as a private member in your MainWindow class again. instead define it as a public slots as below:

class MainWindow : public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
 
protected:
    void changeEvent(QEvent *e);
 
public slots:
    void process();
private:
    Ui::MainWindow *ui;
    void setSignals();
};

class MainWindow : public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();

protected:
    void changeEvent(QEvent *e);

public slots:
    void process();
private:
    Ui::MainWindow *ui;
    void setSignals();
};

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[Harini]

@ saman_artorious


Thank you for u'r suggestion


I did as u suggested but still I'm not getting the process slot in the signal and slot area of the form.please help me.....

[saman_artorious]

@ saman_artorious


Thank you for u'r suggestion


I did as u suggested but still I'm not getting the process slot in the signal and slot area of the form.please help me.....

I am checking your code, it is possible to do that:

void MainWindow::setSignals(){
    connect(ui->next,SIGNAL(clicked()),this,SLOT(process()));

void MainWindow::setSignals(){
    connect(ui->next,SIGNAL(clicked()),this,SLOT(process()));

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so what is the problem!? you have access to your SLOT inside connect. (don't forget to include QObject)

[toufic.dbouk]

Your code is okay.
your application crashes upon clicking the next button because you are creating an info object and showing it but in your info.cpp you dont initailse the UI.

info::info(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::info)
{
    ui->setupUi(this);
}

info::info(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::info)
{
    ui->setupUi(this);
}

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.

The slot process() gets executed upon clicking next so your connect statement works.
Now do whatever you want in that slot.
Something like:

void MainWindow::process()
{
   // this->hide(); /*if you wanna use the hide function you have to take care of info's parent.*/
    info *i = new info(this);
    i->show();
}

void MainWindow::process()
{
   // this->hide(); /*if you wanna use the hide function you have to take care of info's parent.*/
    info *i = new info(this);
    i->show();
}

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Good Luck.

[anda_skoa]

MainWindow:rocess() is a slot, but it is not declared in a slots section

private slots:
   void process();

private slots:
   void process();

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Which of course the application tells you when you start it.

In programming it is generally a good idea to fix errors that are reported by the build and the program.

Cheers,
_

[anda_skoa]

Oh great, I just wasted time on a double poster.

Merging thread as an educational example and making sure the perpertators is recognized as such.

[Harini]

@ anda_skoa

Sorry sir ,I dint get u

[toufic.dbouk]

My previous post shows how to solve the problem. And as mentioned above by anda_skoa your slot process() is declared in the header file not as a Slot. You should declare it under the public or private slots.


Good Luck.