QT QcoreApplication postEvent（）行为

Question

I have written this simple QT mainwindow, only if I pass QString argument to the QKeyEvent, it prints the key, I expect the key to be printed even without QString argument?

section 1 in below code does not seem to work (I don't get the key printed in the QLineEdit field; while section 2 works and "1" is printed! is this normal behavior? what happens to the event when its posted in first section of the code?

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)

{
    ui->setupUi(this);
    this->ui->lineEdit->setFocus();

    Qt::Key key = Qt::Key_1;
    // 1
    QKeyEvent *event = new QKeyEvent (QEvent::KeyPress, key ,Qt::NoModifier); 
    QCoreApplication::postEvent(QWidget::focusWidget(), event); // Does not work! No key is set in the widget
    //
    //2 
    QKeyEvent *event2 = new QKeyEvent(QEvent::KeyPress, key, Qt::NoModifier, QKeySequence(key).toString());
    QCoreApplication::postEvent(QWidget::focusWidget(), event2); // this one works! 

}

Answer 1

Not all key-events have a text representation (delete, curser movement, shortcuts, ...). For those who have one, the QKeyEvent class stores it in its text. You have to provide that text, otherwise its a "textless" event.

QLineEdit will just add the text, and not deduce it from the event type (as can be seen here )