Syntax for Vector of QPushbuttons added to FlowLayout

[Swati777999]

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

1. Where does QScrollArea fit in your widget hierarchy? (Remember that QScrollArea is a widget)
flowLayout ->addWidget(scrollArea); flowLayout is the child Layout.

2. Why do you call childWidget->setLayout(flowLayout); multiple times?
It's by mistake I wrote it. childWidget is the widget for flowLayout. Refer the following code.

    {   int n=20;
    QWidget *parentWidget =new QWidget(this);
    QGridLayout *parentLayout =new QGridLayout(parentWidget);
    parentWidget->setLayout(parentLayout);

    FlowLayout *flowLayout = new FlowLayout();
    parentLayout->addLayout(flowLayout,1,0);  //Adding child layout to parentlayout


    QWidget *childWidget = new QWidget(); //Child Widget for flowLayout
    parentLayout->addWidget(childWidget); //Adding childWidget to parent layout


    QVector <QPushButton *> buttons(n);
    QScrollArea *scrollArea = new QScrollArea(parentWidget);
    flowLayout ->addWidget(scrollArea);


    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);
     }

    childWidget->setLayout(flowLayout);  //setting Layout for the childWidget

    scrollArea->setWidget(childWidget);
    scrollArea->widget()->setEnabled(true);
  
  this->show();
}

I get the following result after making the change. I don't know what the first box is.

[JKSH]

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

1. Where does QScrollArea fit in your widget hierarchy? (Remember that QScrollArea is a widget)
flowLayout ->addWidget(scrollArea); flowLayout is the child Layout.

Your code puts things in this order:

1. scrollArea inside flowLayout
2. flowLayout inside childWidget
3. childWidget inside scrollArea

So which of these objects is meant to be the one "outside"?

I suggest you update your diagram and include QScrollArea in the diagram.

[Swati777999]

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

So which of these objects is meant to be the one "outside"?
I suggest you update your diagram and include QScrollArea in the diagram.

Here's the updated diagram for scrollArea, notice that the scrollArea Widget is in pink color.

[JKSH]

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

Here's the updated diagram for scrollArea, notice that the scrollArea Widget is in pink color.

• According to your diagram, scrollArea is inside childWidget
• According to your code, childWidget is inside scrollArea.

Which one is correct?

Notes:

• I said this before: QScrollArea is a QWidget. You can't put a QScrollArea between your FlowLayout and your buttons.
• In case it's not obvious: QPushButton is also a QWidget.
• Your design is extremely complicated. I suggest you reduce the number of widgets and layouts.

[Swati777999]

@JKSH

I want to set the scrolling functionality for the array of pushbuttons. That's the reason why I put scrollArea inside the flowLayout.

[Pl45m4]

@Swati777999

And where do you want to have your flowLayout?
Your design is really confusing.

How about putting a widget with a flowLayout containing your buttons in your ScrollArea?!
Still don't know if that is what you are trying to achieve.
From you figure, it looks like you have a least 1 or 2 (parent) widgets and layouts more than necessarily needed.

[JKSH]

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

I want to set the scrolling functionality for the array of pushbuttons. That's the reason why I put scrollArea inside the flowLayout.

Then you should:

1. Put the flowLayout in a container/child widget
2. Put that container/child widget in the scrollArea

But before that, simplify your design and remove the widgets and layouts that you don't need. Both myself and @Pl45m4 have asked you to do this. Please don't ignore our words.

[Swati777999]

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

How about putting a widget with a flowLayout containing your buttons in your ScrollArea?!

I don't know if my layout design is the correct one. I should be able to navigate to the buttons at the bottom from the top buttons by scrolling. This is my objective. How can it be achieved?

[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