Qt Creator module learning-event system (event filter)

Qt Creator module learning-event system (event filter)

For event filtering, the event() function can also be performed but only one at a time, so Qt has one event filter, which can filter multiple controls at a time.
Look at the example directly:

bool Widget::eventFilter(QObject *obj,QEvent *ev){
    
    
   QMouseEvent *env = static_cast<QMouseEvent *>(ev);
   
    if(obj==ui->label_2){
    
    
        if(ev->type()==QEvent::MouseMove)
        {
    
    
            ui->label_2->setText(QString("Mouse move:(%1,%2)").arg(env->x()).arg(env->y()));
            return true;
        }
        if(ev->type()==QEvent::MouseButtonPress)
        {
    
    
            ui->label_2->setText(QString("Mouse press:(%1,%2)").arg(env->x()).arg(env->y()));
            return true;
        }
        if(ev->type()==QEvent::MouseButtonRelease)
        {
    
    
            ui->label_2->setText(QString("Mouse release:(%1,%2)").arg(env->x()).arg(env->y()));
            return true;
        }
        else
        {
    
    
            return  QWidget::eventFilter(obj,ev);
        }
    }
    else
    {
    
    
        return  QWidget::eventFilter(obj,ev);
    }
}