Confusion between the usage of 'this' and 'parent'

[Swati777999]

@JKSH

Yes, I remember your advice of giving a dimension to my layout to make it appear on the screen, I was mistakenly putting row,column parameters while creating gridLay as a result of which I was getting errors repeatedly but now , I understood the concept.

gridLay->addWidget(button1,100,120,Qt::Alignment=0x0020);

The third argument gives me an error. How should the value of alignment be used?
Qt::Alignment=0x0020

[J.Hilk]

@Swati777999

gridLay->addWidget(button1,100,120,Qt::Alignment=0x0020);

100,120 does not mean the pixels on your screen, but row/column 100/120

try placing your first widget on column/row 0 and use the actual enum not the integer value as 4th paramter

gridLay->addWidget(button1,0,0,Qt::AlignTop);

[Swati777999]

@J-Hilk

After modifying the existing code, gridLay->addWidget(button1,0,0,Qt::AlignTop);
I can't find any change in my display. :(

[JKSH]

@Swati777999 said in Confusion between the usage of 'this' and 'parent':

My doubt is , even if I comment this->show() in layoutExample.cpp , the widgets in layoutExample.cpp still appear on the screen. How is it possible?

Because you called w.show().

After modifying the existing code, gridLay->addWidget(button1,0,0,Qt::AlignTop);
I can't find any change in my display. :(

First: Instead of QMainWindow, make your widget inherit QWidget. This makes things simpler.

Second: You only put one button in the layout. You should put ALL buttons in the layout. Remember to use different rows/columns for each button.

[Swati777999]

@JKSH

This is the LayoutExample.cpp

LayoutExample::LayoutExample(QWidget *parent)
    : QMainWindow(parent)
{
............
}

In place of QMainWindow, if I put QWidget, it gives an error. For example:

LayoutExample::LayoutExample(QWidget *parent)
    : QWidget(parent)
{
............
}

[Swati777999]

@JKSH said in Confusion between the usage of 'this' and 'parent':

@Swati777999 said in Confusion between the usage of 'this' and 'parent':

My doubt is , even if I comment this->show() in layoutExample.cpp , the widgets in layoutExample.cpp still appear on the screen. How is it possible?

Because you called w.show().

After modifying the existing code, gridLay->addWidget(button1,0,0,Qt::AlignTop);
I can't find any change in my display. :(

First: Instead of QMainWindow, make your widget inherit QWidget. This makes things simpler.

Second: You only put one button in the layout. You should put ALL buttons in the layout. Remember to use different rows/columns for each button.
This is the complete code, please refer to it.

LayoutExample.cpp

LayoutExample::LayoutExample(QWidget *parent)
    : QMainWindow(parent)

{   gridLay = new QGridLayout(this);
    box = new QWidget(this);
    button1=new QPushButton("Click Here",this);
    button2 = new QPushButton("Sign up",this);
    button1->move(200,200);
    button2->move(100,100);

    gridLay->addWidget(box,60,60);
    gridLay->addWidget(button1,0,0,Qt::AlignTop);
    gridLay->addWidget(button2,50,100,Qt::AlignBottom);

    this->setLayout(gridLay);
    this->show();


}

LayoutExample::~LayoutExample()
{
}

[JKSH]

@Swati777999 said in Confusion between the usage of 'this' and 'parent':

In place of QMainWindow, if I put QWidget, it gives an error.

You must update your .h file too.

gridLay->addWidget(box,60,60);
gridLay->addWidget(button1,0,0,Qt::AlignTop);
gridLay->addWidget(button2,50,100,Qt::AlignBottom);

You want to specify row/column number. Not pixel number.

I suggest you use a QVBoxLayout for now. It's simpler than QGridLayout.

[Swati777999]

@JKSH said in Confusion between the usage of 'this' and 'parent':

@Swati777999 said in Confusion between the usage of 'this' and 'parent':

You must update your .h file too.
Done! It works now!

gridLay->addWidget(box,60,60);
gridLay->addWidget(button1,0,0,Qt::AlignTop);
gridLay->addWidget(button2,50,100,Qt::AlignBottom);

You want to specify row/column number. Not pixel number.
Noted!

I suggest you use a QVBoxLayout for now. It's simpler than QGridLayout.
Okay

[Pl45m4]

@Swati777999

As I've said, because you still show your LayoutExample in your main with w.show().... and this will show the MainWindow widget and ALL its children including your buttons.

Edit:
@JKSH sry :) Missed the sentence in your reply where you also said that

[JKSH]

@Pl45m4 said in Confusion between the usage of 'this' and 'parent':

@JKSH sry :) Missed the sentence in your reply where you also said that

No prob! It's good to have multiple confirm the same thing