QLabel::clicked()

[sabeesh]

Hi,
I am using QT 4.2.2. I have a label in my main window. I want a "QLabel::clicked()" signal for my label, ie, i want to call a function when i click on a lable. How can I do that.

[vermarajeev]

Hi,
I am using QT 4.2.2. I have a label in my main window. I want a "QLabel::clicked()" signal for my label, ie, i want to call a function when i click on a lable. How can I do that.

There is no clicked signal in QLabel. What you can do is create your own QLabel class and override mousePressEvent to fire a clicked signal and catch it in your defined slot.

[sabeesh]

Hi,
Not clear!!!!!!!!!!!

[vermarajeev]

Hi,
Not clear!!!!!!!!!!!


myLabel::myLabel( const QString & text, QWidget * parent )
:QLabel(parent)
{
connect( this, SIGNAL( clicked() ), this, SLOT( slotClicked() ) );
}
void myLabel::mousePressEvent ( QMouseEvent * event )
{
emit clicked();
}
void myLabel::slotClicked()
{
qDebug()<<"Clicked";
}

[sabeesh]

Hi,
When I give this code, qt display some errors. Can you give me a small discreption aout this code. because, i am a new comer in QT!!!!!

[marcel]

When I give this code, qt display some errors.

How do you "give" the code?

That is a QLabel subclass.
You have to define your own class, and add those methods to it and also the signal.

That code is no not complete. It is just a suggestion.
You will have to embed it in your application.

Regards

[vermarajeev]

Ok, here is the full code

//.h

class myLabel : public QLabel
{
Q_OBJECT
public:
myLabel( const QString & text, QWidget * parent = 0 );
~myLabel(){}

signals:
void clicked();

public slots:
void slotClicked();

protected:
void mousePressEvent ( QMouseEvent * event ) ;

};
#endif

.cpp

myLabel::myLabel( const QString & text, QWidget * parent )
:QLabel(parent)
{
connect( this, SIGNAL( clicked() ), this, SLOT( slotClicked() ) );
}

void myLabel::slotClicked()
{
qDebug()<<"Clicked";
}

void myLabel::mousePressEvent ( QMouseEvent * event )
{
emit clicked();
}

In your mainWindows.cpp in the constructor add this


MainWindow::MainWindow(QWidget* parent)
: QMainWindow(parent)
{
myLabel* m_label = new myLabel(this);
}


I have not tested the code so please correct the code if you get any errors
Thanks

[jbarrena]

Hi there!!

And how is it possible for the Widget to catch the clicked signal from the label???

Thanks for the help!!!

Best regards!

[gun4boy]

code of vermarajeev works well for me ;)

[Sven]

Hi there!!

And how is it possible for the Widget to catch the clicked signal from the label???

Thanks for the help!!!

Best regards!



MainWindow::MainWindow(QWidget* parent)
: QMainWindow(parent)
{
myLabel* m_label = new myLabel(this);
}

If you use this example you can catch it like this:


MainWindow::MainWindow(QWidget* parent)
: QMainWindow(parent)
{
myLabel* m_label = new myLabel(this);
connect(myLabel, SIGNAL(clicked()), SLOT(myActionWhenMyLabelHasBeenClicked()));
}

[lotek]

Hi,

only one remark:

The "real click" will be better simulated if you will use the
mouseReleaseEvent(QMouseEvent *e) instead of mousePressEvent(QMouseEvent *e)


regards

me :)

[dogbear]

I agree with Lotek.
A mouse "click" is traditionally a full press-then-release event series.
Interpreting a click on a mouse press disallows the user from canceling the click when they drag the mouse away from the item, amongst other things.
Just my two-cents.
doggy

[gadlol]

And how to check which label has been clicked if have many????

[Talei]

Using above example if You connect multiple instances of myLabel object into one slot then within that slot You can use sender() to determine what myLabel object send the signal. To have full access You can cast it lik:


myLabel *Label = qobject_cast<myLabel *>( this->sender() );
Label->setText( QString( "This sender is: %1" ).arg( this->sender()->objectName() ) );

Label is pointer to the object that send signal.

[study24816]

thanks to this thread! I'm having the same problem with my project and this works just fine for me. But, in my application, besides emitting the signal after the mouse is clicked/released, I also need to know the coordinates of the clicked point. Is there any way to program this??
I'm new to Qt and is learning :D.

[d_stranz]

Did you read the docs on QMouseEvent? There are 7 different methods to give you information about the position of the mouse.

If the slot listening for the clicked() signal needs to know the mouse position, then change the clicked signal to send the position as an argument:



// myLabel.h
signals:
void clicked( const QPos & );

// myLabel.cpp:

void myLabel::mouseReleaseEvent( QMouseEvent * event )
{
emit clicked( event->pos() );
}

[study24816]

I think I've foudn the answer. the pointer *event to QMouseEvent stores the relevant information about the event mousepress/release. I gotta read more about QMouseEvent.

Thanks