Handling multiple forms

[msmihai]

Hello everybody . I'm new to this forum ( because it's the first time for me using QT but i'm pretty sure i'll be using it regularly from now ) . I followed a couple of tutorials, wrote some simple GUI applications but I could'nt find an answer for my problem .

I have to ui's ( dlg1.ui and dlg2.ui ). dlg1.ui is the main window of my application(project type: MainWindow) , with the name Form1 , and dlg2.ui is another window( project type Widget ) .

Here is how my projects files look like .
main.cpp


#include <qapplication>
#include "app.h"

int main(int argc,char *argv[])
{
QApplication app(argc,argv);
App1 dialog;
dialog.show();
return app.exec();
}



app.h


#ifndef APP_H
#define APP_H

#include "ui_dlg1.h"
#include "ui_dlg2.h"

class App1:public QMainWindow,private Ui::Form1
{
Q_OBJECT
public:
App1();
public slots:
void button_clicked();
};

class App2:public QWidget,private Ui::Form2
{
Q_OBJECT
public:
App2(QWidget *parent = 0);
};

#endif


app.cpp


#include <QtGui>
#include "app.h"

App1::App1()
{
setupUi(this);
connect(pushButton,SIGNAL(clicked()),this,SLOT(but ton_clicked()));
}

App2::App2(QWidget *parent)
{
setupUi(this);
}

void App1::button_clicked()
{
App2 form2(this);
form2.show();
}



This code works just fine but when I press the button , Form2 appears for a very very short time and then it's being destroyed . Why this happens ? And how can I correct it so that Form2 shows as a modal window ( no interraction with Form1 being possible till Form2 is being closed ) .

Furthermore, how can I make two forms communicate with each other ? My idea was a global variabiles in app.cpp that each form can see .

I hope I was clear enough . Have a great day !

[caduel]

you create form2 on the stack. When the scope is left, it is destroyed (and thus disappears.)

You have two possibilites.
i) Make it a modal dialog (ie inherit from QDialog and call exec())
ii) allocate form2 on the heap (using new, and ideally passing a QObject parent object to make sure the object gets deleted in time)

HTH

[msmihai]

Thanks a lot caduel, i used dynamic allocation and it worked .
Still, i have one more question .
Let's say i Press de button, Form2 appears ( modally , that means i Form1 is disabled ).
I input some text into Form2's LineEdit and then i press a button, also on Form2. When I press the button, Form2 closes and Form1 becomes active again .

What I want to do now is to take the text from LineEdit on Form2 and show it somewhere in Form1 . I managed to get the actual text using a global variabile. But ... how can i detect that Form2 has closed ? For example, let's say in Form1 I also have a LineEdit. When I close Form2 , I want Form1 LineEdit to have the text from Form2 LineEdit .

How can I accomplish this ?

I tried the followind code:



void App1::button_clicked()
{
App2 *form2 = new App2(this);
form2->show();
QMessageBox msg;
msg.setText(text);
msg.exec();
}


hoping that the code after form2->show() would be executed after Form2 was closed.Unfortunately, the code executes as soon as Form2 appears on the screen.

[caduel]

override the okay() slot (if using a QDialog): store your lineedit's contents in your dialog.
at the call site (when exec() returned), call a getter-function to access that text. do not use globals for that. it is ugly and will cause you trouble. (e.g. you can not use two such dialogs that way).

[msmihai]

could you give me an example ? i'm relative new to QT ... I don't fully understand what you explain to me ... and no .. I have a QmainWindow and a QWidget.