QLabel text not updating

[mounipanditi]

Hi i want to update the text of QLabel when the key is pressed, i am unable to see the output on the UI when ever the Key is pressed.
Here i s my code

WIDGET.H

#ifndef WIDGET_H
#define WIDGET_H

#include<QtGui>
#include <QEvent>
#include<QTextEdit>
#include<QLabel>
#include<QWidget>
#include <QKeyEvent>

class Widget : public QWidget
{
    Q_OBJECT

public:

    Widget(QWidget *parent = 0);
   QLabel *lab;
    
protected:
    bool event(QEvent *);
};

#endif // WIDGET_H

WIDGET.CPP

#include "widget.h"
#include <QDebug>
#include<QLabel>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
        resize(1000,1000);
        qDebug() << "Constructor";
        QPalette palet=this->palette();
        QPixmap pix(":9.jpeg");
        QPixmap pix_scaled(pix.scaled(500,500,Qt::IgnoreAspectRatio, Qt::SmoothTransformation));
        palet.setBrush(QPalette::Window, QBrush(pix_scaled));
        setPalette(palet);
        setAutoFillBackground(true);

        lab=new QLabel;
        lab->setParent(this);
        lab->setGeometry(30,30,310,60);
        lab->setText("SETTING TEXTTT");
}

bool Widget::event(QEvent *e)
{
if(e->type()==QEvent::KeyRelease)
 {
          QKeyEvent *ke = static_cast<QKeyEvent *>(e);
          int keyValR = ke->key();
          qDebug() << "Released key value is : " << keyValR;

         switch(keyValR)
         {
             case Qt::Key_F1:
                  qDebug()<<"F1 Key Pressed";
                  lab->setText("KeyPressed is F1");
                  break;
            case Qt::Key_Q:
                  qDebug()<<"Q Key Pressed";
                  lab->setText("KeyPressed is Q");
                  break;
            default:
                   qDebug("No Key Pressed");
       
         }
    }
}

Here is the output image URL

https://s17.postimg.org/z9uo6n2in/Screenshot_from_2017_02_13_17_09_31.png

Please correct my Code if there are any mistakes

[dheerendra]

Code looks good to me at least. Can u try calling lab.update() function ? Also as a side note you can directly implement keyreleaseevent in widget class instead of going through event() function.

[m.sue]

Hi,
you can do such things in so-called event filter functions, similar to the function event, that you defined but with another signature, like:

bool Widget::eventFilter(QObject *obj, QEvent *e)
{
if(e->type()==QEvent::KeyRelease)
 {
          QKeyEvent *ke = static_cast<QKeyEvent *>(e);
          int keyValR = ke->key();
          qDebug() << "Released key value is : " << keyValR;

         switch(keyValR)
         {
             case Qt::Key_F1:
                  qDebug()<<"F1 Key Pressed";
                  lab->setText("KeyPressed is F1");
                  break;
            case Qt::Key_Q:
                  qDebug()<<"Q Key Pressed";
                  lab->setText("KeyPressed is Q");
                  break;
            default:
                   qDebug("No Key Pressed");
            }
       	// standard event processing
	return QObject::eventFilter(obj, e);
}

And you will have to call something like:
lab->installEventFilter(this) and
lab->removeEventFilter(this)
in contrctor and destructor of the Widget class.
-Michael

[mounipanditi]

@dheerendra

I have tried update() too but of no use and i want to share something more

If i exapnd the Widget size then i am able to see the updated text

Image before Update of Label Text
https://s17.postimg.org/z9uo6n2in/Screenshot_from_2017_02_13_17_09_31.png

Image after Update of Label Text
https://s14.postimg.org/aaamuwaqp/Screenshot_from_2017_02_13_17_34_50.png

To say i have just exapnded the size of Widget a pinch that's all

And i have already tried the approach of keyreleaseevent, but i want to find out why this approach is not working.

[mounipanditi]

@m.sue

thanks for replying me, i have tried what you have said but the control is not entering into the IF condition

if(e->type()==QEvent::KeyRelease)
{
  //Not entering into the condition
}

[m.sue]

Hi,
I looked at the event function and it is probably the same as using an event filter. But in your function event as in any virtual function you should use somewhere the base class implementation like
return QWidget::event(e)
at the end.
-Michael.

[mounipanditi]

@m.sue said in QLabel text not updating:

Thanks Michael it worked and the text is updating.