Getting position of mouse click in a QLabel

问题

What is the best (as in simplest) way to obtain the pos of a mousePressedEvent in a QLabel? (Or basically just obtain the location of a mouse click relative to a QLabel widget)

EDIT

I tried what Frank suggested in this way:

bool MainWindow::eventFilter(QObject *someOb, QEvent *ev)
{
if(someOb == ui->label && ev->type() == QEvent::MouseButtonPress)
{
    QMouseEvent *me = static_cast<QMouseEvent *>(ev);
    QPoint coordinates = me->pos();
    //do stuff
    return true;
}
else return false;
}

However, I receive the compile error invalid static_cast from type 'QEvent*' to type 'const QMouseEvent*' on the line where I try to declare me. Any ideas what I'm doing wrong here?

回答1:

You could subclass QLabel and reimplement mousePressEvent(QMouseEvent*). Or use an event filter:

bool OneOfMyClasses::eventFilter( QObject* watched, QEvent* event ) {
    if ( watched != label )
        return false;
    if ( event->type() != QEvent::MouseButtonPress )
        return false;
    const QMouseEvent* const me = static_cast<const QMouseEvent*>( event );
    //might want to check the buttons here
    const QPoint p = me->pos(); //...or ->globalPos();
    ...
    return false;
}


label->installEventFilter( watcher ); // watcher is the OneOfMyClasses instance supposed to do the filtering.

The advantage of event filtering is that is more flexible and doesn't require subclassing. But if you need custom behavior as a result of the received event anyway or already have a subclass, its more straightforward to just reimplement fooEvent().