Access the UI, from multiple windows.

SGaist

Hi,

The usual fix to this one is: don't create static QWidget based objects.

Loc888

@SGaist I dont know what you mean.

mrjj

@Loc888
Hi
You cannot have global Widgets as they are NOT
allow to be constructed before QApplication in main.
They must be pointers and you can first new them After application is created.

SGaist

If you have anything that looks like static MyClass thingy where MyClass is derived from QWidget, then remove it.

Loc888

@mrjj I tried by reference, and this happend:

Error: 'QWidget& QWidget::operator=(const QWidget&)' is private
Class &operator=(const Class &) Q_DECL_EQ_DELETE;
^

mingw48_32\include\QtWidgets\qwidget.h:728: in expansion of macro 'Q_DISABLE_COPY'
Q_DISABLE_COPY(QWidget)
^

It happend in this line Class &operator=(const Class &) Q_DECL_EQ_DELETE;

I try later with pointers, and will see what happend.

SGaist

For more information why, read this.

Loc888

@SGaist

Now i tried with pointers, error :

error: invalid operands of types 'Settings_Window*' and 'Settings_Window*' to binary 'operator*'
A* &Settings_Widget;
^

void MainWindow::Get_Window_Data(Settings_Window* A)
{

A* &Settings_Widget;

}

What i did wrong?

mrjj

@Loc888
Hi
Why not just
Settings_Window* MainWindow::Get_Window_Data()
{
return Settings_Widget; // Settings_Widget is * (pointer) ?
}

Loc888

@mrjj

It run at least, but is not working. If i check something, then press the button with this code, nothing happened. Probably is another copy.
I am tired, tomorrow i try something else.

Is this the way how i should use it?

MainWindow B;


if(B.Get_Window_Data()->ui->Checker_Box_01->isChecked())
{

    //Do something

}

mrjj

Hi
Yes but im old school and always check pointers
so i would do

MainWindow B; // this should not be a second instance but the one you (might) create in main.cpp

Settings_Window * win=B.Get_Window_Data();

if (!win) {
qDebug() << "NULL ptr from Get_Window_Data";
return;
}
if(win->ui->Checker_Box_01->isChecked())
{
    //Do something
}
if(win->ui->Checker_Box_XX->isChecked())
{
    //Do something
}

However, the UI variable is private so unless the using class is friend, its not allowed.
So you make make UI public ( bad design )
or provide access functions for the widgets.

jsulm

@Loc888 said in Access the UI, from multiple windows.:

B.Get_Window_Data()->ui->Checker_Box_01->isChecked()

From software design point of view this is so bad!
You should not expose internal details of your MainWindow like that.
Add public methods to MainWindow which return needed invormation without exposing internal implementation details.
Example:

class MainWindow...
{
public:
    bool isSomethingActivated()
    {
        return ui->Checker_Box_01->isChecked();
    }
}

MainWindow B;
if(B.isSomethingActivated())
{
    //Do something
}

Now, the user of MainWindow does not have to know anything about how the MainWindow is designed (what UI elements it has for example) - it just calls a public interface method to get the information. Usn't this much nicer? One more advantage of this approach: if you later change your MainWindow UI the caller of the MainWindow will not be affected.
Example:

class MainWindow...
{
public:
    bool isSomethingActivated()
    {
        // You decided that the condition should be different
        return ui->Checker_Box_01->isChecked() && ui->Checker_Box_02->isChecked();
    }
}

// No need to change the caller of MainWindow
MainWindow B;
if(B.isSomethingActivated())
{
    //Do something
}

mrjj

@jsulm
And we come full circle \o/
I told OP that 4 days ago, but he seems unwilling to
create access functions :)
Maybe seeing your good example, OP will feel the joy of good design
and do it the right way.

Loc888

@mrjj

It makes me a little bit mad, why everything need's to be complicated.
So, in main window can i use something like that:

  B.Get_Window_Data()->ui->Checker_Box_01->isChecked()

But in other window, i need to do it in other way?

jsulm

@Loc888 You should no access internal implementation details of one window (class) from another. It is not related to Qt, this are simply software design basics...
And what is complicated about it? Is my example really complicated? What you're trying to do is much more complicated and error prone. Why do you want to know in window A how window B is constructed? Why not simply define simple APIs to communicate between windows? To be honest code like what you're trying to write would not pass code reviews in the company where I'm working.

Loc888

@mrjj Listen, i show you my code, cuz i am getting a little bit crazy, i can't create it in main.cpp, becasuse then how can i show it?

In MainWindow.h i have

    Settings_Window* Get_Window_Data();

     Settings_Window* Settings_Widget = new Settings_Window;

MainWindow.cpp

Settings_Window* MainWindow::Get_Window_Data()
{

    return Settings_Widget;

}

Window1

MainWindow B;

Settings_Window S;


if(B.Get_Window_Data()->ui->Checker_01->isChecked())
{

  
}

Loc888

@jsulm I never gonna work for anybody from software design. I am doing it more like hobby.

Loc888

@mrjj This method is not working

Settings_Window* MainWindow::Get_Window_Data()
{

return Settings_Widget;

}

If i press the checkerbox, it should be setted to true

void Settings_Window::on_CheckerBox_clicked()
{

    B->Get_Window_Data()->ui->CheckerBox->setChecked(true);

}

Then when i go to window one, and press the button

void Window1::on_Button001_clicked()
{

MainWindow* B = new MainWindow;


if(B->Get_Window_Data()->ui->Auto_Reset_Data_Timer->isChecked())
{

    //do something

  }

}

I don't understand all your methods, so if anyone can, please correct this stuff, cuz i have enough.

mrjj

In what way not working ?
it just returns the pointer to your
Settings_Widget so only way it can fail is to return null.

I wonder here
void Window1::on_Button001_clicked()
{

MainWindow* B = new MainWindow; << you create new one. ?

so you dont have one already ?
Or is that on purpose ?
So each time you click you make a new window ?

Loc888

@mrjj I have another button to activate and show that window.

MainWindow* B = new MainWindow;

No,i have already one window.
I just use this to get MainWindow method, and try to set checkerBox as true but from ther.

If i copy the same code from that button, and paste it to Window1, it's working, but is not the way how it should work, i dont want to set it ther....

I mean:

MainWindow* B = new MainWindow;

B->Get_Window_Data()->ui->CheckerBox->setChecked(true);


if(B->Get_Window_Data()->ui->Auto_Reset_Data_Timer->isChecked())
{

    //do something

  }

When i say "Is not working", i mean when i click the button, checkBox should return true, and when i compare it in another window, checkBox returns false, i think because i set it to another copy... How,i don't know. It should return Settings_Widget in window1.

mrjj

Hi
Im sorry if we frustrated you. We just know from experience
what works bad over time so that is why we seem so keen to do it the right way.
Lets start over.
ok, so you have a normal main.cpp

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

  return a.exec();
}

so w is mainwindow
and it has the true Settings_Window embedded.

So we need Window1 to have access to MainWins Settings_Window and not a new copy.
So Window1 should NOT new one it self but get the one from Mainwin.

I assume Mainwindow also creates and show Window1
You can change its constructor to take a Settings_Window * and it can then store it for accessing.

Like

#include "Settings_Window.h"  // so it knows the TYPE ( make to use right name if not that)

class Window1 : public QMainWindow
{
    Q_OBJECT
Settings_Window *GivenToMe;
public:
    explicit Window1 (QWidget *parent = 0, Settings_Window *TheTrueOne) {
GivenToMe = TheTrueOne; // store the pointer for later
}
    ~Window1 ();
....
};

// then in MainWin where you show the Window1
void MainWindow::ShowSettings() {
Window1 * Win1= new Window1(this,   & S_Window ); // the & to make it pointer
Win1->show();
}

now inside
void Window1::SomeButtonClick() {
// you now have GivenToMe that is the Settings_Widget from MainWindow
now you can call public functions in it
if ( GivenToMe -> SomeFunc() ) ...

}

If you do not want to create public access functions but go directly via UI you have to make it public
so in Settings_Window.h

private:
Ui::Settings_Windowui;
must be
public:
Ui::Settings_Windowui;

to allow
if ( GivenToMe -> ui->CheckerBox->isChecked() ) ...

--

What we tried to make you do was to add public access function in mainwindow
so you would say
if ( GivenToMe ->GetSettingForX() ) ( and it just returns the ui->Checker_01->isChecked() )

but if you really not want that, then you can make ui public and the syntax you want is then possible
even if its not best practice/bad idea/design.

Hope this helps. :)