promoted widgets using QT designer is not calling its constructor

[Ratheendrans]

Dear All,

I made a subclass of QLineEdit class and implemented its constructor and keyPressEvent event handler,then I promoted one of the instances of QLineEdit to subclass with QT Designer by right clicking and selecting the promote option. I am able to call keyPressEvent() method in my application. however the constructor of this subclass is never called.

header file.

class printlineEdit : public QLineEdit
{
    //Q_OBJECT
 
public:
//signals:
//      void escapePress();
public:
 
    printlineEdit(QWidget *parent = 0);
    void keyPressEvent( QKeyEvent *event );
    unsigned int ValuePut,val;
 
};

class printlineEdit : public QLineEdit
{
    //Q_OBJECT

public:
//signals:
//      void escapePress();
public:

    printlineEdit(QWidget *parent = 0);
    void keyPressEvent( QKeyEvent *event );
    unsigned int ValuePut,val;

};

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its corresponding c++ file.

printlineEdit::printlineEdit(QWidget *parent):QLineEdit(parent)
{
ValuePut=0;
//selectionStart ();
//setCursorPosition(0);
printf("Inside printline constr\n");
}
 
void printlineEdit::keyPressEvent(QKeyEvent *event)
{
    bool flag=0;
    QString ch("");
 
    switch(event->key())
    {
        case Qt::Key_Left:
            break;
        case Qt::Key_Right:
 
            break;
        case Qt::Key_Up:
            break;
        case Qt::Key_Down:
 
           break;
        case Qt::Key_Return:
           flag=1;
           printf("Enter Pressed\n");
           break;
      }
     }
}

printlineEdit::printlineEdit(QWidget *parent):QLineEdit(parent)
{
ValuePut=0;
//selectionStart ();
//setCursorPosition(0);
printf("Inside printline constr\n");
}

void printlineEdit::keyPressEvent(QKeyEvent *event)
{
    bool flag=0;
    QString ch("");

    switch(event->key())
    {
        case Qt::Key_Left:
            break;
        case Qt::Key_Right:

            break;
        case Qt::Key_Up:
            break;
        case Qt::Key_Down:

           break;
        case Qt::Key_Return:
           flag=1;
           printf("Enter Pressed\n");
           break;
      }
     }
}

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Now for the above code the constructor printlineEdit(QWidget *parent) is never called.

Kindly tell me how to implement a constructor in these scenario.

Ratheendran

[wysota]

How do you know it is never called?

[stampede]

Maybe other constructor for QLineEdit is called, have you tried to implement the other one ?

class printlineEdit : public QLineEdit
{
    //Q_OBJECT
 
public:
//signals:
//      void escapePress();
public:
 
    printlineEdit(QWidget *parent = 0);
    printlineEdit(const QString& text, QWidget *parent = 0);
...
...
// .cpp
printlineEdit::printlineEdit(const QString& text, QWidget *parent):QLineEdit(text,parent)
{
ValuePut=0;
//selectionStart ();
//setCursorPosition(0);
printf("Inside printline constr 2\n");
}

class printlineEdit : public QLineEdit
{
    //Q_OBJECT
 
public:
//signals:
//      void escapePress();
public:
 
    printlineEdit(QWidget *parent = 0);
    printlineEdit(const QString& text, QWidget *parent = 0);
...
...
// .cpp
printlineEdit::printlineEdit(const QString& text, QWidget *parent):QLineEdit(text,parent)
{
ValuePut=0;
//selectionStart ();
//setCursorPosition(0);
printf("Inside printline constr 2\n");
}

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[wysota]

uic only calls the constructor that takes a parent:

void setupUi(QWidget *Form)
    {
        if (Form->objectName().isEmpty())
            Form->setObjectName(QString::fromUtf8("Form"));
        Form->resize(400, 300);
        lineEdit = new printlineEdit(Form);
        lineEdit->setObjectName(QString::fromUtf8("lineEdit"));
        lineEdit->setGeometry(QRect(80, 40, 113, 20));
 
        retranslateUi(Form);
 
        QMetaObject::connectSlotsByName(Form);
    } // setupUi

void setupUi(QWidget *Form)
    {
        if (Form->objectName().isEmpty())
            Form->setObjectName(QString::fromUtf8("Form"));
        Form->resize(400, 300);
        lineEdit = new printlineEdit(Form);
        lineEdit->setObjectName(QString::fromUtf8("lineEdit"));
        lineEdit->setGeometry(QRect(80, 40, 113, 20));

        retranslateUi(Form);

        QMetaObject::connectSlotsByName(Form);
    } // setupUi

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[stampede]

uic only calls the constructor that takes a parent

You are right
Take a look into the ui_*.h file for this form, this way you'll know what is called for your line edit.

[Ratheendrans]

Thanks for your support.

I was able to figure out the issue.

I deleted the promoted widget and created them again,so the text message which I update in the constructor is now visible.

issue is caused because,I used ui designer to put the default text, once I compiled,then I removed the text from ui designer and implemented it in constructor using setText() method. This was creating the confusion.

Another thing I want to ask is there way to call a user defined constructor using the same method.

Ratheendran

[wysota]

No, Designer always calls the constructor with a parent argument.