TableLayout in the centralwindow

[Swati777999]

@jsulm
I get this message with my existing code. I don't understand what it exactly means.

"QWidget::setLayout: Attempting to set QLayout "" on MainWindow "", which already has a layout"

[Swati777999]

@JonB
I used
centralWidget()->setLayout(layout); instead of
this ->setLayout(monitorGLayout);

At least, I can see something working but the newest layout overlaps the existing layout with the following message
QWidget::setLayout: Attempting to set QLayout "" on QWidget "", when the QLayout already has a parent
flashing on the screen of Application output.

I don't understand how this syntax is able to reflect changes - centralWidget()->setLayout(layout);

[Thank You]

@Swati777999
As @JonB said

QMainWindow::setCentralWidget(QWidget *widget) with just a plain QWidget you create,

• Create a widget suppose "myWidget"
• Create a layout
• Add other widgets to the layout
• Set layout to myWidget
• set myWidget as centralWidget

QWidget *myWidget = new QWidget();
QGridLayout *tableLayout = new QGridLayout();


// suppose you want to add button to it 
/  https://doc.qt.io/qt-5/qgridlayout.html#addWidget-1 

QPushButton * button = new QPushButton("hello");
tableLayout->addWidget(button,0,0);


myWidget->setLayout(tableLayout);
QMainWindow::setCentralWidget(myWidget);

[Swati777999]

@Thank-You

Thanks for your answer.

My task is to show a table (which is just a view).

You've added an interactive widget to your layout which is a push-button but I just want to display the table in the format shown above. How can that be achieved?

[jsulm]

@Swati777999 said in TableLayout in the centralwindow:

How can that be achieved?

Using https://doc.qt.io/qt-5/qtablewidget.html or https://doc.qt.io/qt-5/qtableview.html maybe?

[Thank You]

@Swati777999
In place of QPushButton just use either QTableView or QTableWidget and edit the positions of rows and columns in addWidget(widget, Row, Column)
Widget can be anything like table , button , label anything. So you can create instance of it and just put it in place of widget something like

tableLayout->addWidget(firstTable,0,0);
tableLayout->addWidget(secondTable,2,0);
tableLayout->addWidget(thirdTable,0,2);

where firstTable secondTable and thirdTable are your tables

Just One tip:
If you are working with simple data then choosing QTableWidget would be easier and if you are working with some big data and want to use model then go for QTableView

https://doc.qt.io/qt-5/qtablewidget.html
https://doc.qt.io/qt-5/qtableview.html

[Swati777999]

@Thank-You

Thanks, it helped me for creating a basic layout.

I am now trying for the view of the table; like resizing and making division for creating rows and columns.

[Swati777999]

@Thank-You

for making the size of the table to fit to the size of the widget, I used the following
myWidget->adjustSize();

but it does not produce the result

[jsulm]

@Swati777999 Did you put myWidget in a layout?

[Swati777999]

@jsulm No
I have used QMainWindow::setCentralWidget(myWidget);

[Thank You]

@Swati777999

This is final output you are gonna see

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include<QTableWidget>
#include<QGridLayout>
#include<QVBoxLayout>
#include<QLabel>



QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
    QWidget *myWidget;
    QGridLayout *tableLayout;
    QTableWidget *firstTable, *secondTable,*thirdTable;
    QWidget *compoundWidget;
    QVBoxLayout *compoundLayout;
    QLabel *titleOfCompound;
};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

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

    myWidget = new QWidget();
    // this is our main widget which we will set as central widget
    tableLayout = new QGridLayout();
    // this is layout for our myWidget which is like grid as it's name suggests

    firstTable = new QTableWidget();
    secondTable = new QTableWidget();
    thirdTable = new QTableWidget();
    // these are just basic tables which are also widgets.


    compoundWidget = new QWidget();
    // compoundWidget is also a widget but we will add more widgets inside it. In this case we are inserting table and label
    compoundLayout = new QVBoxLayout(compoundWidget);
    // This is layout for compoundWidget

    titleOfCompound = new QLabel("This is title");
    // this is just for showing you that we can put any widgets inside another widget

    compoundLayout->addWidget(titleOfCompound);
    compoundLayout->addWidget(thirdTable);
    // this puts table and title to compoundWidget

    compoundWidget->setLayout(compoundLayout);
    // this sets compoundLayout to compoundWidget : Remember we have added two widgets in compoundLayout so they will be shown

    tableLayout->addWidget(firstTable,0,0);
    // we want first table to be at first so row = 0 ; column =0;
    tableLayout->addWidget(secondTable,2,0);
    // we want second table to be at left bottom so row = 2; column =0; // we can use any number. If there aren't widgets in middle it will adapt
    tableLayout->addWidget(compoundWidget,0,2);
    // we want compoundWidget consisting (label and table) binded by compound Layout to be at right so row = 0; column = 2;
    myWidget->setLayout(tableLayout);
    //setting main layout to our myWidget

    setCentralWidget(myWidget);
    // now setting that myWidget as our central or main widget
    // if we remove this line nothing will show up which means we are telling QMainWindow to set this as centralWidget
// You will not be able to see anything if you forget to add layout because we have added all our widget to layout


}

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

If you remove to set centralwidget then it will result in this

I haven't touched main.cpp

See this image

If this couldn't help you understand I can't

[Swati777999]

@Thank-You

Thank you so much. such an elaborate explanation!! I appreciate your efforts in explaining the concept.

I reached up to this by following your logic. Now, I've to resize the table inside the widget at (0,0) to its size and I've used QTableWidget to draw the table, so can't use resizeColumnToContents(int column) for resizing. Any suggestion for this change?

[Christian Ehrlicher]

@Swati777999 said in TableLayout in the centralwindow:

so can't use resizeColumnToContents(int column) for resizing.

Why? QTableWidget derives from QTableView: https://doc.qt.io/qt-5/qtableview.html#resizeColumnToContents

[Thank You]

@Swati777999

https://forum.qt.io/topic/26799/qtablewidget-shrink-to-fit/10
I guess you will get your answer here.
Don't use TableWidget for big datas. Just use it for learning purpose. It's so much functionality in tableview

[Swati777999]

@Christian-Ehrlicher I don't know, it gives an error in my code when I use it for QTableWidget.

[jsulm]

@Swati777999 said in TableLayout in the centralwindow:

it gives an error

Post the error and code causing it...

[Thank You]

@Swati777999
If that is not fully related to the original question posting another question would be helpful to newcomers.

I use it for QTableWidget.

QTableWidget or QTableView