how to show and hide Qlabel continuously on mainwindow

[prasad1001]

Hello all,
I am new to Qt, please tell me how to show and hide the Qlabel message continuously on my mainwindow...

Here is my code..

MainWindow.cpp

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    label=ui->label;
 
display();
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::display()
{
    while(1)
    {
        label->show();
        sleep(1000);
        label->hide();
    }
}

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

display();
}

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

void MainWindow::display()
{
    while(1)
    {
        label->show();
        sleep(1000);
        label->hide();
    }
}

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when i run the program mainwindow is not comming...and no errors are comming..
Please help me..
Thank you.

[Lesiok]

First of all loop in MainWindow::display is "never ending story". Thus MainWindow constructor is blocking application.
Second UI need working event loop but You are blocking her. Read about QTimer.

[prasad1001]

Thank you for the reply....can u please provide with an example code..
I didn't get ur point..

Thanks in advance..

[Lesiok]

Method display should be defined as slot and looks like :

void MainWindow::display()
{
    label->setVisible(!label->isVisible());// Set the status of the opposite
    QTimer::singleShot(500,this,SLOT(display()));// call display() after 500 ms
}

void MainWindow::display()
{
    label->setVisible(!label->isVisible());// Set the status of the opposite
    QTimer::singleShot(500,this,SLOT(display()));// call display() after 500 ms
}

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[prasad1001]

Method display should be defined as slot and looks like :

void MainWindow::display()
{
    label->setVisible(!label->isVisible());// Set the status of the opposite
    QTimer::singleShot(500,this,SLOT(display()));// call display() after 500 ms
}

void MainWindow::display()
{
    label->setVisible(!label->isVisible());// Set the status of the opposite
    QTimer::singleShot(500,this,SLOT(display()));// call display() after 500 ms
}

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Thanks for the reply sir..

I was placed that method...but when i run my program..it is showing that..
"The program has unexpectedly finished."

Thanks in advance..

[ChrisW67]

Run your program in your debugger. When it crashes look at where it crashed in the back trace you will likely be given.