communicate data between two windows

Albator

Hello qt people,

I have two mainwindows.ui and in the first windows I make a 2+2 calculation and I display this result in my first window in a qlabel and I would like to be able to display this result in my second window! how do I do it?

//seconde_p2.cpp
#include "seconde_p2.h"

#include "mainwindow.h"

#include "ui_seconde_p2.h"


seconde_p2::seconde_p2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p2)
{
    ui->setupUi(this);
    
    int a,b,c;
    a=2;
    b=2;
    c=a+b;
    ui->lineEdit->setText(QString::number(c)); 


}

seconde_p2::~seconde_p2()
{
    delete ui;
}

//seconde_p3.cpp
#include "seconde_p3.h"
#include "seconde_p2.h"

#include "ui_seconde_p3.h"


seconde_p3::seconde_p3(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p3)
{
    ui->setupUi(this);
    
     // how use c here 
}

seconde_p3::~seconde_p3()
{
    delete ui;
}

SGaist

Hi,

You can use Signals and Slots, or a simple setter, or pass the value as a parameter of the constructor.

mrjj

Hi
One way is to give it to the window when you create it.
Change its constructor to accept extra parameter
and give it to it when constructed.

int c= xxxx
seconde_p3 * win3 = new seconde_p3(this, c):
win3->show();

Albator

This post is deleted!

Albator

I try getter/setter :

in my first windows second_p2

// seconde_p2.h

    //getter
    int get_c() const{return c;}
    //setter
    void set_c(int val);

protected :
    int c;

// seconde_p2.cpp
seconde_p2::seconde_p2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p2)
{
    ui->setupUi(this);

    c=3;


}

yes for this example setter is useless and in my seconde page alias seconde_p3 i have :

// seconde_p3.cpp

seconde_p3::seconde_p3(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p3)
{
    ui->setupUi(this);



seconde_p2* test = new seconde_p2();
test->get_c();
qDebug()<< test;



}

i have 0 error but ! in the console i can look this :
seconde_p2(0x1bf26bf8, name="seconde_p2")

and it's not my c=3 :(

Bonnie

@Albator said in communicate data between two windows:

i have 0 error but ! in the console i can look this :
seconde_p2(0x1bf26bf8, name="seconde_p2")

and it's not my c=3 :(

[EDITED]
Sorry, didn't understand your code until now...

qDebug()<< test->get_c();

That should output a "3"

Albator

yes it's exact ! thanks all for your help ! :)))

Albator

i have a little problem, for a int it's okay but to make a getter with a qvector<double> it doesn't work.

seconde_p2.h
 //getter
    int get_c() const{return c;}
    QVector<double> get_vector() const{return fer;}
    //setter
    //void set_c(int val);

protected :
    int c=6;
    QVector<double> fer;

// seconde_p2.cpp
seconde_p2::seconde_p2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p2)
{
    ui->setupUi(this);

    c=3;
    fer={ 1, 2, 3, 4, 5, 6, 7 };


}

and in the seconde_p3.cpp

seconde_p3::seconde_p3(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p3)
{
    ui->setupUi(this);

seconde_p2* test = new seconde_p2();
seconde_p2* test1 = new seconde_p2();

test->get_vector();
qDebug()<<"qvector<double> display"<< test->get_vector();

test1->get_c();
qDebug()<<"int display"<< test1->get_c();


}

in the console :

qvector<double> display QVector() // why he is empty ?
int display 3

Albator

This post is deleted!

mrjj

Hi
Should work as you put value in the vector, in the constructor.

what does test->get_vector();
do ?

maybe you return empty list there ?

Albator

@Albator said in communicate data between two windows:

QVector<double> get_vector() const{return fer;}

and fer is not empty, it works for c ...

Q139

Is it wrong to use global window pointers and access setters getters via pointer instead of signals&slots?

Albator

i want use getter in first but if i have not the choice maybe i will change my solution, it works for c so it should work for the qvector

mrjj

@Albator
yes must also work for Qvector same way as int.

Albator

@mrjj
that's what I think, but who knows where the pangolin is that's standing in the way of my code?

mrjj

@Albator
so while it returns empty list and the same time in same code and
in same run, it can return 3 for c ?
it seems impossible :)

Albator

@mrjj
in first i put my value :

seconde_p2::seconde_p2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p2)
{
    ui->setupUi(this);

    c=3;
    fer={ 1, 2, 3, 4, 5, 6, 7 };
    qDebug() << fer;


}

and in second i have a button who call the other windows :

void seconde_p2::on_page3_clicked()
{
    p3 = new seconde_p3(this);
    p3->show();
}

and for the final in the second_p3.cpp (my other window), i use my getter and display :

seconde_p3::seconde_p3(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p3)
{
    ui->setupUi(this);

seconde_p2* test = new seconde_p2();
seconde_p2* test1 = new seconde_p2();

test->get_data1();
qDebug()<<"qvector<double> display"<< test->get_data1();

test1->get_c();
qDebug()<<"int display"<< test1->get_c();


}

and tadaaaa : c is displayed correctly and fer is empty
my conclusion ? it's a sad day :(

Christian Ehrlicher

@Albator said in communicate data between two windows:

seconde_p2* test = new seconde_p2();
seconde_p2* test1 = new seconde_p2();

C++ basics - this are new local instances - it won't help at all. You have to pass the pointer from the other object to this class. This is basic c++ stuff - programming with Qt without this basic knowledge will not work.

Albator

@Christian-Ehrlicher
excuse me I try and thanks to your advices I advance and yes sometimes I miss my bases :)