QKeyEvent

[sonuani]

hi,
If my QLineEdit text length is 0 and if i press enter.Then a message has to be dispayed.
I tried the below code.Its not working.
Whats wrong with the code??

QKeyEvent keyy(QEvent::FocusIn,0,Qt::KeypadModifier,"0",false,1);
 
if((Varname->text().length()==0) && (keyy.key() == Qt::Key_Enter))
{
}

QKeyEvent keyy(QEvent::FocusIn,0,Qt::KeypadModifier,"0",false,1);

if((Varname->text().length()==0) && (keyy.key() == Qt::Key_Enter))
{
}

To copy to clipboard, switch view to plain text mode 

[jpn]

See QLineEdit::returnPressed().

[sonuani]

Hi,
I did like the below code.But still its not working.

connect( Lineeditname, SIGNAL( returnPressed() ),            
		this, SLOT( Display() ) );
 
void Classname::Display()
{
	if(Lineeditname->text().length()==0) 
	{}
}

connect( Lineeditname, SIGNAL( returnPressed() ),            
		this, SLOT( Display() ) );

void Classname::Display()
{
	if(Lineeditname->text().length()==0) 
	{}
}

To copy to clipboard, switch view to plain text mode 

[jpn]

What does "not working" mean? Does the slot get called?

[sonuani]

I m getting a msg "No such slot named display" in the command prompt and nothing is happening in the UI

[jpn]

Did you declared Display() as slot? Did you add required Q_OBJECT macro? For more details, see Signals and Slots.

[momesana]

Try out the following example by saving it as a single file called main.cpp and compiling and executing it.

#include <QtGui>
 
class MainWindow : public QMainWindow
{
       Q_OBJECT
      public:
                 MainWindow(QWidget* parent=0) : QMainWindow(parent)
               {
                    QWidget* cw = new QWidget;
                       QVBoxLayout* lo = new QVBoxLayout(cw);
                       QLabel* lb = new QLabel("Enter text below and press <b>Enter</b>");
                       lb->setWordWrap(true);
                     m_le = new QLineEdit;
                     connect(m_le, SIGNAL(returnPressed()), this, SLOT(display())); // What you need
                     m_tb = new QTextBrowser;
                     // layout
                     lo->addWidget(lb);
                     lo->addWidget(m_le);
                     lo->addWidget(m_tb);
                     // set central widget
                     setCentralWidget(cw);
                }
      private slots: // display() is a declared a slot!!!
               void display()
                {
                    if (m_le->text() == "")
                         QMessageBox::warning(this, "Empty string", "You have to enter something!");
                    else
                          m_tb->setText(m_le->text());
               }
      private:
                QLineEdit* m_le;
                QTextBrowser* m_tb;
};
 
int main(int argc, char *argv[])
{
   QApplication app(argc, argv);
   MainWindow mw;
   mw.show();
   return app.exec();
}
 
#include "main.moc"

#include <QtGui>

class MainWindow : public QMainWindow
{
       Q_OBJECT
      public:
                 MainWindow(QWidget* parent=0) : QMainWindow(parent)
               {
                    QWidget* cw = new QWidget;
                       QVBoxLayout* lo = new QVBoxLayout(cw);
                       QLabel* lb = new QLabel("Enter text below and press <b>Enter</b>");
                       lb->setWordWrap(true);
                     m_le = new QLineEdit;
                     connect(m_le, SIGNAL(returnPressed()), this, SLOT(display())); // What you need
                     m_tb = new QTextBrowser;
                     // layout
                     lo->addWidget(lb);
                     lo->addWidget(m_le);
                     lo->addWidget(m_tb);
                     // set central widget
                     setCentralWidget(cw);
                }
      private slots: // display() is a declared a slot!!!
               void display()
                {
                    if (m_le->text() == "")
                         QMessageBox::warning(this, "Empty string", "You have to enter something!");
                    else
                          m_tb->setText(m_le->text());
               }
      private:
                QLineEdit* m_le;
                QTextBrowser* m_tb;
};
      
int main(int argc, char *argv[])
{
   QApplication app(argc, argv);
   MainWindow mw;
   mw.show();
   return app.exec();
}

#include "main.moc"

To copy to clipboard, switch view to plain text mode 

[sonuani]

hi,
I tried adding Q_OBJECT to my program.
I got the below linker errors.Wt is wrong here?Am i suppose to add anything??

code:

class classname : public QDialog ,Ui_dialog
{ 
	Q_OBJECT
}

class classname : public QDialog ,Ui_dialog
{ 
	Q_OBJECT
}

To copy to clipboard, switch view to plain text mode 

Linker Errors:

classname .obj : error LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __thiscall classname ::metaObject(void)const " (?metaObject@classname @@UBEPBUQMetaObject@@XZ)

classname .obj : error LNK2001: unresolved external symbol "public: virtual void * __thiscall classname ::qt_metacast(char const *)" (?qt_metacast@classname @@UAEPAXPBD@Z)

classname .obj : error LNK2001: unresolved external symbol "public: virtual int __thiscall classname ::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@classname @@UAEHW4Call@QMetaObject@@HPAPAX@Z)

[jpn]

You must re-run qmake after adding or removing Q_OBJECT. It will generate required moc rules to your makefile (or visual studio project file). Also, make sure the header file you added Q_OBJECT macro is listed in .pro file.