How to use both setValidator() and setInputMask() for QLineEdit in Qt?

Question

I have a line edit where the user has to enter in the 12-hour time format. This is a touch based application and I have my own keyboard and this keyboard does not have the ":" (colon) character. So, I am using an Input Mask for that purpose. But I have only setInputMask( 99:99 ) option which allows the user to enter any number whereas I have to restrict the user to the 12-hour format.

I went through some examples with QRegexp but I couldn't have the ":" like in the Input Mask. Can anyone point me on how to implement?

@hank No I can't use it here. Requirements :) – jxgn Mar 31 '16 at 05:40 — jxgn, Mar 31 '16 at 05:40

score 0 · Answer 1 · answered Mar 31 '16 at 08:04

Although the Qt Docs explicitly say that we shall "use masks together with validators" if we want range control in out QLineEdits, this seems to be not that trivial. At least other people has similar problems. But mybe this helps:

Subclass the QLineEdit and override focusInEvent() and setValidator() as follows:

----------------- mylineedit.h ----------------------

#ifndef MYLINEEDIT_H
#define MYLINEEDIT_H

#include <QLineEdit>
#include <QFocusEvent>
#include <QRegExpValidator>

class MyLineEdit : public QLineEdit
{
    Q_OBJECT

private:

    const QValidator *validator;

public:

    MyLineEdit(QWidget *parent = 0);

    void setValidator(const QValidator *v);

protected:

    void focusInEvent(QFocusEvent *e);
};

#endif // MYLINEEDIT_H

------------------- mylineedit.cpp -------------------

#include "mylineedit.h"

MyLineEdit::MyLineEdit(QWidget *parent): QLineEdit(parent)
{

}

void MyLineEdit::setValidator(const QValidator *v)
{
    validator = v;
    QLineEdit::setValidator(v);
}

void MyLineEdit::focusInEvent(QFocusEvent *e)
{
    Q_UNUSED(e);
    clear();
    setInputMask("");
    setValidator(validator);
}

For the MyLineEdit object itself we use a QRegExp to allow only to enter time in 12 hour format without a colon at this point: 1152 e.g. When the user ends editing the lineedit gets an InpuMask of the form "HH:HH" which makes 1152 to 11:52. The focus is cleared. If the user focuses again to the lineedit, it is cleared and the QRegExp is set again and the user enteres the new time 1245 e.g. and so on...

--------------------- rootwindow.h --------------------

#ifndef ROOTWINDOW_H
#define ROOTWINDOW_H

#include "mylineedit.h"
#include <QMainWindow>
#include <QWidget>
#include <QtDebug>

class RootWindow : public QMainWindow
{
    Q_OBJECT

private:

    QWidget *widgetCentral;
    MyLineEdit *line;

public:

    RootWindow(QWidget *parent = 0);
    ~RootWindow();

private slots:

    void slotLineEdited();
};

#endif // ROOTWINDOW_H

-------------- rootwindow.cpp ----------------------

#include "rootwindow.h"

RootWindow::RootWindow(QWidget *parent): QMainWindow(parent)
{
    setCentralWidget(widgetCentral = new QWidget);

    line = new MyLineEdit(widgetCentral);
    line->setValidator(new QRegExpValidator(  QRegExp("[0][0-9][0-5][0-9]|[1][0-2][0-5][0-9]")  ));

    connect(line, SIGNAL(editingFinished()), this, SLOT(slotLineEdited()));
}

RootWindow::~RootWindow()
{

}

void RootWindow::slotLineEdited()
{
    line->setInputMask("HH:HH");
    line->clearFocus();
}

---------------------- main.cpp --------------------------

#include "rootwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    RootWindow w;
    w.show();

    return a.exec();
}

It seems a little over the top but actually it is not that much new code and you do not need a colon key on your keyboard.

How to use both setValidator() and setInputMask() for QLineEdit in Qt?

1 Answers1