How to restrict QLineEdit to take "comma" and "plus" as input value?

[kishore_hemmady]

Hi,,

how can I avoid entering comma (,) and plus (+) to QLineEdit field in my Qt ui application??
and also QSpinBox to not to take + (plus)??

[LeLev]

hi @kishore_hemmady ,
see void QLineEdit::setValidator(const QValidator *v) http://doc.qt.io/qt-5/qlineedit.html#setValidator

QRegExp exp = QRegExp("your regExp");
QRegExpValidator v = QRegExpValidator(exp,this);
 yourLineEdit.setValidator(v);

[kishore_hemmady]

thank you @LeLev

please tell me how can i set range for this field using the below snippet?

QRegExp rx("-?\\d{1,3}");
QValidator *validator = new QRegExpValidator(rx, this);
ui->VideoHeight->setValidator(validator);

I want to set the range between 1 to 100.

[Gojir4]

@kishore_hemmady Hi,

Better to use QIntValidator in this case:

QValidator *validator = new QIntValidator(1, 100, this);
// the edit lineedit will only accept integers between 1 and 100 
edit->setValidator(validator);

[kishore_hemmady]

hi @Gojir4 ,

thank you,
i had used the same but ,i was able to enter comma (,)and plus (+) symbol if i use the above code,which i don't want.

[mad-hatter]

Hello,

You could install an eventFilter on your lineEdit and trap the comma, '+' and '-' sign and use the int validator as well.

Regards

[SGaist]

Hi,

What is your widget purpose ?

[KillerSmath]

@kishore_hemmady

You can create a RegularExpression to accept just 0 or 1-99 or 100

QRegExp regExp = QRegExp("^(0|[1-9][0-9]?|100)$");

| = OR
? = OPTIONAL

NOTE: if you are using Qt5.*, i suggest you to use QRegularExpression instead of QRegExp, because QRegExp is an old class of regular expression of Qt4 :)
http://doc.qt.io/qt-5/qregularexpression.html#notes-for-qregexp-users

[kishore_hemmady]

Hi @SGaist

its a variable , i have to set it like this,
ui->height->setValidator(newQIntValidator(minValue,maxValue, this));
if i use this then the height field will take + and , values.

minValue and maxValue values are system dependent

[SGaist]

If you still have a comma that you can enter then there's something else that's wrong neither QIntValidator nor QSpinBox allows that kind of number.

What is the problem with the plus sign ?

[KillerSmath]

@kishore_hemmady
If you really need to avoid the + signal and just accept numbers.

1) You can create a custom QIntValidator and reimplement the validate function to accept what you need.

// customintvalidator.h
#include <QIntValidator>

class CustomIntValidator : public QIntValidator {
public:
    CustomIntValidator (int bottom, int top, QObject * parent) : QIntValidator(bottom, top, parent) {}

    QValidator::State validate(QString &s, int &pos) const {
        Q_UNUSED(pos);
        if (s.isEmpty()){
            return QValidator::Intermediate; // accept but is not valid
        }

        if( s.startsWith("+") ){
            return QValidator::Invalid;
        }

        if( bottom() < 0 && s.startsWith("-") && s.length() == 1 ){
            return QValidator::Intermediate;
        }

        // check number

        bool isNumber;
        int value = locale().toInt(s, &isNumber);

        if (isNumber && bottom() <= value && value <= top()) {
            return QValidator::Acceptable;
        }

        return QValidator::Invalid;
    }

};

// mainwindow.cpp
ui->lineEdit->setValidator(new CustomIntValidator(-100 , 100, this));

This custom IntValidator accepts positive and negative numbers incluinding -0 interpreted as 0
And ignore comma, dot and plus simbols.

2) You can create a filter to capture the Comma and Plus Keydown event

// filterobject.h
#include <QEvent>
#include <QKeyEvent>
#include <QObject>

class FilterObject : public QObject {
public:
    explicit FilterObject(QObject *parent = 0) : QObject(parent){
    }
    
    bool eventFilter(QObject *object, QEvent *event)
    {
        Q_UNUSED(object);
        if (event->type() == QEvent::KeyPress) {
            QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
            switch(keyEvent->key()){
            case Qt::Key_Plus:
                return true;
            case Qt::Key_Comma:
                return true;
            default:
                return false;
            }
        }
        return false;
    }
};

// mainwindow.cpp
ui->lineEdit->installEventFilter(new FilterObject(ui->lineEdit));

I don't believe these are the best solutions for this problem but works.

[kishore_hemmady]

hi @KillerSmath
thank you for your answer.