Syntax for Vector of QPushbuttons added to FlowLayout

[Swati777999]

@JKSH and @Pl45m4

Yes, check the revised code as below:

{
QWidget *flowWidget = new QWidget(this);
FlowLayout *flowLayout = new FlowLayout();
flowWidget->setLayout(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);
}

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

It gives me following output :

scrollArea inside another window .

If I declare scroll widget as below:
QScrollArea *scroll =new QScrollArea();
I get a blank window.

If I declare scroll widget as follows:
QScrollArea *scroll =new QScrollArea(flowWidget);
my program crashes.

[JKSH]

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

Yes, check the revised code as below:

Good! It is much cleaner now.

scrollArea inside another window .

That's because your scrollArea is a child widget but you did not put it inside a layout.

Questions:

1. In your latest code, who is scrollArea's parent?
2. Do you need scrollArea to be a child widget? In other words, does scrollArea need a parent?
3. How would you make scrollArea a top-level widget?

[Swati777999]

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

That's because your scrollArea is a **child widget** but you did not put it inside a **layout.
If I write flowLayout ->addWidget(scroll); , my program ends forcefully.

Questions:
1. In your latest code, who is scrollArea's parent?
Ans: the mainwindow (I've set its parent to be this . As mentioned above, if I set it's parent to be flowWidget,my program crashes.

2. Do you need scrollArea to be a child widget? In other words, does scrollArea need a parent?
Ans : It's like the main window is the parent ; its child is flowWidget whose children are buttons , scroll is to be applied to flowWidget such that scroll functionality works for all the buttons simultaneously.

Note : I should be able to navigate to the buttons at the bottom from the top buttons by scrolling. This is my objective.

3. How would you make scrollArea a top-level widget?
Ans: It was just a part of my experimentation, as it is not working neither for scroll->setWidget(flowWidget) nor for QScrollArea *scroll = new QScrollArea (flowWidget);

I hope it makes much sense now/

[Pl45m4]

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

I hope it makes much sense now

Not really, at least not to me.

For what purpose is the FlowWidget now?
Can't you just assign the flowLayout to your mainWindow?

Note: scrollArea can handle one entire widget (with all of its sub-widgets and layouts). As far as I understood, your buttons are on multiple widgets, am I right?!
Don't know how your "scroll from top buttons down to bottom buttons" should work. At least when the entire widget is as big as the parent window.

Edit:
Quick fix: set your main widget (whatever it might be, maybe scrollArea?!) as centralWidget with setCentralWidget(.....), so the content covers your whole mainWindow.

[Swati777999]

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

For what purpose is the FlowWidget now?

Can't you just assign the flowLayout to your mainWindow?
Yes, this is what I did at the first place but I followed the suggestion of @JKSH for implementing the scrollArea for all button widgets.

Then you should:
Put the flowLayout in a container/child widget
Put that container/child widget in the scrollArea

So, I put the entire flowlayout inside a flowWidget.

Note: scrollArea can handle one entire widget (with all of its sub-widgets and layouts). As far as I understood, your buttons are on multiple widgets, am I right?!
Yes, my buttons are arrays of widgets. I want to enable scrolling property just the way I use this link of this forum ; to be able to navigate from top to bottom of this page where the contents of my windows are buttons.

Don't know how your "scroll from top buttons down to bottom buttons" should work. At least when the entire widgets is as big as the parent window.

I want to navigate to the bottom of the mainwindow through the scrollbar where the contents of the mainWindow are buttons , just like the following picture; scrollbar in the bottom and right side. In the figure, there are 20 push buttons but I can only view 12 out of them in my window.

[Pl45m4]

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

where the contents of the mainWindow are buttons

The content (= centralwidget) of your mainWindow should be your scrollArea then. And inside this scrollArea you place the widget with your buttons.

[Swati777999]

@Pl45m4
The content (= centralwidget) of your mainWindow should be your scrollArea then. And inside this scrollArea you place the widget with your buttons.
Okay, Let me write the whole function according to your suggestion.

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

QWidget *flowWidget = new QWidget();
FlowLayout *flowLayout = new FlowLayout();
flowWidget->setLayout(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);

}

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

a->setCentralWidget(scroll);


a->show();

setWindowTitle(tr("Flow Layout"));
}

I obviously,get 2 windows from the above code, Window1 corresponding to this by default window which is blank.
Window2 is as shown below

scroll Area is applied to the window but the flowLayout seems not to be working and the widgets take vertical Layout. Can you help me to fix this?

[Pl45m4]

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

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

QWidget *flowWidget = new QWidget();
FlowLayout *flowLayout = new FlowLayout();
flowWidget->setLayout(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);

}

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

a->setCentralWidget(scroll);

a->show();

That's not what I suggested....

The window with the title flowLayout IS your MainWindow, right?! Why you created another one ?

I obviously,get 2 windows from the above code, Window1 corresponding to this by default window which is blank.

Yes, not very surprising from above code...

Window::Window()

What is this class? Your first mainWindow? Then you dont need to create another QMainWindow *a= new QMainWindow(this);
inside this class. Remove it and call this->setCentralWidget(....) instead (assuming Window is a QMainWindow class).

[JKSH]

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

scroll Area is applied to the window but the flowLayout seems not to be working and the widgets take vertical Layout. Can you help me to fix this?

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

[Swati777999]

@Pl45m4 said in Syntax for Vector of QPushbuttons added to FlowLayout:
Actually, I'm using the example file of flowLayout given in the section of Examples in Qt Creator where class Window used [subclass of QWidget].

The window with the title flowLayout IS your MainWindow, right?! Why you created another one ?
As you can see, there are two windows with names as flowLayout and FlowLayout . My mainwindow should be Flow Layout for which I wrote the following code:
I needed to add scroll functionality to the following code.

    #include<QScrollArea>	
    Window::Window
{
    FlowLayout *flowLayout = new FlowLayout(this);
    int n=20;
    QVector <QPushButton *> buttons(n);

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

           flowLayout->addWidget(pb);
      }
this ->show();
}

What is this class? Your first mainWindow? Then you dont need to create another QMainWindow *a= new QMainWindow(this);
inside this class. Remove it and call this->setCentralWidget(....) instead (assuming Window is a QMainWindow class).
I used QMainWindow *a= new QMainWindow(this); because it seemed to be working partially.

[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...