Syntax for Vector of QPushbuttons added to FlowLayout

[Swati777999]

@Pl45m4 said in Syntax for Vector of QPushbuttons added to FlowLayout:

inside this class. Remove it and call this->setCentralWidget(....) instead (assuming Window is a QMainWindow class).

this->setCentralWidget(....) this gives me error as this is an object of Window class which is a subclass of QWidget.
setCentralWidget(.....) can be applied to the object of QMainWindow.

[Swati777999]

@JKSH said in Syntax for Vector of QPushbuttons added to FlowLayout:
Your flowWidget is too narrow -- that's why the flow layout can't put buttons side-by-side. Give it a larger minimum width.
Remember: The width of the QScrollArea is not the same as the width of the widget it holds

This works like a charm! Thanks a ton! I was thinking it to be the fault of my design and made it too complicated.

Just a doubt about the number of buttons appearing/row.

Window::Window
{
QMainWindow *a= new QMainWindow(this);

QWidget *flowWidget = new QWidget();
FlowLayout *flowLayout = new FlowLayout();
flowWidget->setLayout(flowLayout);
flowWidget ->setMinimumSize(1200,1200);
int n=20;
QVector <QPushButton *> buttons(n);

for (int ii=0;ii<n;ii++)
{
    QPushButton * pb = new QPushButton(); // creating buttons

       pb->setMinimumSize(200,200);
       buttons.push_back(pb); // adding buttons to qvector

       flowLayout->addWidget(pb);
}

QScrollArea *scroll =new QScrollArea();
scroll->setWidget(flowWidget);

a->setCentralWidget(scroll);
a->show();
}

This is the result I get in flowLayout window.

From the figure, I get 5 buttons per row but as per the following lines , shouldn't I be getting 6 buttons/row ( 1200/200=6)

flowWidget ->setMinimumSize(1200,1200); // size of widget
pb->setMinimumSize(200,200); //size of buttons

[Christian Ehrlicher]

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

From the figure, I get 5 buttons per row but as per the following lines , shouldn't I be getting 6 buttons/row ( 1200/200=6)

And you see that the widgets have some margins between them? So why should 6 widgets with 200x each + margins fit into 1200px??

[Swati777999]

@Christian-Ehrlicher That's right but by intuition/observation, I can say that, in the above figure, one more button can easily fit in. What do you think?

[JKSH]

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

by intuition/observation, I can say that, in the above figure, one more button can easily fit in.

Apply the same intuition to your previous case:

Then, apply the same explanation that I gave you in my previous post.

Then, explain to us what's happening.

This works like a charm! Thanks a ton! I was thinking it to be the fault of my design and made it too complicated.

Great!

Complicated design does not cause code to stop working. However, it does make life very difficult for you.

Window::Window
{
QMainWindow *a= new QMainWindow(this);

You are making your design extremely complicated again... You don't need a Window plus a QMainWindow plus a QScrollArea.

Before you proceed any further, simplify your design first!

[Swati777999]

@JKSH said in Syntax for Vector of QPushbuttons added to FlowLayout:

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

by intuition/observation, I can say that, in the above figure, one more button can easily fit in.

Apply the same intuition to your previous case:

Then, apply the same explanation that I gave you in my previous post.
Then, explain to us what's happening.

In this case , the setminimumsize() for the widget is not used ,that's why the buttons take a vertical layout.

You are making your design extremely complicated again... You don't need a Window plus a QMainWindow plus a QScrollArea.Before you proceed any further, simplify your design first!

With the objects of QMainWindow,QScrollArea , I am getting the desired result as I have suppressed /commented window.show(); in main.cpp

Follow main.cpp below:

#include <QApplication>

#include "window.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    Window window;
#if defined(Q_OS_SYMBIAN)
    window.showMaximized();
#else
    //window.show();
#endif
    return app.exec();
}

[jsulm]

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

I am getting the desired result as I have suppressed /commented window.show(); in main.cpp

Because your Window creates and shows a new QMainWindow! Why?!
I think you was already told several times that there is no need to create two windows.
Why don't you remove

QMainWindow *a= new QMainWindow(this);

and show Window?

[Swati777999]

@JKSH Now, I'm trying out the second part of this design

You can see the bigger red-rectangle is what I was designing above. Now,I've to design the whole layout.Here's my code-

Window::Window()

{
QMainWindow *a= new QMainWindow(this);

QWidget *WindowWidget= new QWidget();
WindowWidget->setMinimumSize(2000,2000);

QVBoxLayout *WindowLayout = new QVBoxLayout(WindowWidget);
QScrollArea *scroll =new QScrollArea();

QLabel *WindowHeading = new QLabel("Experimenting with Scrollbar in Flow Layout");
WindowLayout->addWidget(WindowHeading);
WindowLayout->setAlignment(WindowHeading,Qt::AlignCenter);


QWidget *flowWidget = new QWidget();
FlowLayout *flowLayout = new FlowLayout();

int n=20;
QVector <QPushButton *> buttons(n);

for (int ii=0;ii<n;ii++)
{
    QPushButton * pb = new QPushButton(); // creating buttons

       pb->setMinimumSize(200,200);
       buttons.push_back(pb); // adding buttons to qvector

       flowLayout->addWidget(pb);

}
flowWidget->setLayout(flowLayout);
flowWidget ->setMinimumSize(1200,1200);
WindowLayout->addWidget(flowWidget);

//scroll->setWidget(flowWidget);

a->setCentralWidget(WindowWidget);
a->show();
}

can't see it working! :'(

[Swati777999]

@jsulm said in Syntax for Vector of QPushbuttons added to FlowLayout:

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

I am getting the desired result as I have suppressed /commented window.show(); in main.cpp

Because your Window creates and shows a new QMainWindow! Why?!
I think you was already told several times that there is no need to create two windows.

Why don't you remove
QMainWindow *a= new QMainWindow(this); ?
As already mentioned before, Window class is a sub-class of QWidget ,for setting scrolling option , I need the object of QMainWindow , that's the reason why I created the object a of QMainWindow.

[jsulm]

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

I need the object of QMainWindow

Then your Window should subclass QMainWindow, not QWidget...

[Swati777999]

@jsulm said in Syntax for Vector of QPushbuttons added to FlowLayout:

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

I need the object of QMainWindow

Then your Window should subclass QMainWindow, not QWidget...

Actually, I am making changes in the FlowLayout Example given in the Example section of QtCreator. That's why doing in this way.

[jsulm]

@Swati777999 If you mean this example https://code.qt.io/cgit/qt/qtbase.git/tree/examples/widgets/layouts/flowlayout?h=5.15 then I can't see where a QMainWindow instance is created. Window is simply a QWidget, but if you need QMainWindow you can inherit from it instead of QWidget.
Keep in mind that examples are exactly that: examples. You need to adopt them to your needs properly.

[Swati777999]

@jsulm said in Syntax for Vector of QPushbuttons added to FlowLayout:
@Swati777999 If you mean this example https://code.qt.io/cgit/qt/qtbase.git/tree/examples/widgets/layouts/flowlayout?h=5.15 then I can't see where a QMainWindow instance is created. Window is simply a QWidget, but if you need QMainWindow you can inherit from it instead of QWidget.

Yes , right , this example I was referring to. Window is a subclass of QWidget here and I created QMainWindow to utilise scroll property.

[jsulm]

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

Window is a subclass of QWidget here and I created QMainWindow to utilise scroll property

And this is the wrong approach.
Subclass QMainWindow and do not create any additional QMainWindow instances.

[Swati777999]

@jsulm got it. Let me try.

[Swati777999]

@jsulm said in Syntax for Vector of QPushbuttons added to FlowLayout:

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

Window is a subclass of QWidget here and I created QMainWindow to utilise scroll property

And this is the wrong approach.
Subclass QMainWindow and do not create any additional QMainWindow instances.
Done!

Window::Window()

{
QScrollArea *scroll =new QScrollArea();
QWidget *flowWidget = new QWidget();
FlowLayout *flowLayout = new FlowLayout();

int n=20;
QVector <QPushButton *> buttons(n);

for (int ii=0;ii<n;ii++)
{
    QPushButton * pb = new QPushButton(); // creating buttons
       pb->setMinimumSize(200,200);
       buttons.push_back(pb); // adding buttons to qvector
       flowLayout->addWidget(pb);

}

flowWidget ->setMinimumSize(1200,1200);
scroll->setWidget(flowWidget);
flowWidget->setLayout(flowLayout);
this->setCentralWidget(scroll);
this->show();
}

It's working fine with Window as the subclass of QMainWindow.

[Swati777999]

@jsulm

I am doing part-2 for the following layout :

blank display unfortunately!

{
QWidget *WindowWidget= new QWidget(this);
WindowWidget->setMinimumSize(2000,2000);

QVBoxLayout *WindowLayout = new QVBoxLayout(WindowWidget);


QLabel *WindowHeading = new QLabel("Experimenting with Scrollbar in Flow Layout");
WindowLayout->addWidget(WindowHeading);
WindowLayout->setAlignment(WindowHeading,Qt::AlignCenter);
QScrollArea *scroll =new QScrollArea();

QWidget *flowWidget = new QWidget();
flowWidget ->setMinimumSize(1200,1200);
FlowLayout *flowLayout = new FlowLayout();


int n=20;
QVector <QPushButton *> buttons(n);

for (int ii=0;ii<n;ii++)
{
    QPushButton * pb = new QPushButton(); // creating buttons

       pb->setMinimumSize(200,200);
       buttons.push_back(pb); // adding buttons to qvector

       flowLayout->addWidget(pb);

}
flowWidget->setLayout(flowLayout);
WindowLayout->addWidget(flowWidget);
scroll->setWidget(flowWidget);
this->setCentralWidget(WindowWidget);


this->show();
}

[Pl45m4]

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

blank display unfortunately!

Blank in which way?
How does your main.cpp look right now?

[JKSH]

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

In this case , the setminimumsize() for the widget is not used ,that's why the buttons take a vertical layout.

That's an incomplete answer.

1. You also get a "vertical layout" if you call flowWidget->setMinimumSize(100, 100). Why?
2. What is the minimum size that you need to get 2 buttons per row?

Now, I'm trying out the second part of this design

No, don't do this yet.

Before you proceed any further, simplify your design first!

With the objects of QMainWindow, QScrollArea, I am getting the desired result

You still have an extremely complicated way of getting the desired result. You need to know how to achieve your result after removing both Window and QMainWindow from your code.

Until you can achieve this, it is a bad idea to try out the second part of this design.

Your diagram is wrong. The QScrollArea is not the orange scrollbars. The QScrollArea is the big red rectangle. Does this make sense?

[Swati777999]

@JKSH said in Syntax for Vector of QPushbuttons added to FlowLayout:

@Swati777999 said in Syntax for Vector of QPushbuttons added to FlowLayout:

In this case , the setminimumsize() for the widget is not used ,that's why the buttons take a vertical layout.

That's an incomplete answer.

1. You also get a "vertical layout" if you call flowWidget->setMinimumSize(100, 100). Why?
2. What is the minimum size that you need to get 2 buttons per row?

Now, I'm trying out the second part of this design

No, don't do this yet.

Here's the simplified code for the entire design . I created a new project scrollAreaApp with the base class as QMainWindow
scrollAreaApp.cpp

#include "scrollareaapp.h"

ScrollAreaApp::ScrollAreaApp(QWidget *parent)
    : QMainWindow(parent)
{
    QWidget *flowWidget = new QWidget();
    FlowLayout *flowLayout = new FlowLayout();
    flowWidget->setLayout(flowLayout);
    flowWidget ->setMinimumSize(1200,1200);
    int n=20;
    QVector <QPushButton *> buttons(n);

    for (int ii=0;ii<n;ii++)
    {
        QPushButton * pb = new QPushButton(); // creating buttons

           pb->setMinimumSize(200,200);
           buttons.push_back(pb); // adding buttons to qvector

           flowLayout->addWidget(pb);

    }

    QWidget *WindowWidget= new QWidget(this);
    WindowWidget->setMinimumSize(1000,1000);

    QVBoxLayout *WindowLayout = new QVBoxLayout(WindowWidget);

    QLabel *WindowHeading = new QLabel("Experimenting with Scrollbar in Flow Layout");

    WindowLayout->addWidget(WindowHeading);
    WindowLayout->setAlignment(WindowHeading,Qt::AlignLeft);
    WindowLayout->addWidget(flowWidget);
    
    QScrollArea *scroll =new QScrollArea();
    scroll->setWidget(WindowWidget);
    this->setCentralWidget(scroll);
    this->show();
} 

I am getting the desired result.