Question

I have a QLineEdit widget in my menubar which shows the text “search by ID” by default. How can I implement a MouseClicked event handler for the QLineEdit, such that when I click on the LineEdit widget, the default text is cleared and user can enter the text that he wants to search?.

so far

#ifndef SEARCH_H
#define SEARCH_H
#include<QLineEdit>

class search : public QLineEdit
{
        signals:
                void clicked();

        protected:
                void mousePressEvent(QMouseEvent *);
};
#endif

Answer 1

You just need to connect QLineEdit::mousePressEvent ( QMouseEvent * e ) signal with function. When this signal will be emited, clear QLineEdit in your function. Simply, isn’t it?

EDIT

Or if u have

void mousePressEvent(QMouseEvent *);

in your widget, all what you need is write definition for that method. When user press mouse over QLineEdit, this function will be invoked. Like:

void search::mousePressEvent(QMouseEvent *e)
{
    myQLineEdit->setText("");
}

EDIT 2

Then try to do it this way:

class YourWidget : public QLineEdit
{
    Q_OBJECT

    protected:

    void focusInEvent(QFocusEvent* e);
};

and

void YourWidget::focusInEvent(QFocusEvent* e)
{    
    if (e->reason() == Qt::MouseFocusReason)    
    {
      myQLineEdit->setText("");
    }

    // You might also call the parent method.
    QLineEdit::focusInEvent(e);
}