QIntValidator

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You can prevent invalid text from being entered into a lineEdit using a validator. This example demonstrates QIntValidator, which only allows integers to be entered into the lineEdit.

Validator.cpp

<br />#include <QApplication>

#include "form.h"

int main(int argc, char *argv[])<br />{<br /> QApplication app(argc, argv);<br /> Form form;

form.show();<br /> return app.exec();<br />}<br />

form.h

<br />#ifndef FORM_H<br />#define FORM_H

#include "ui_form.h"

class Form : public QWidget, private Ui::Form<br />{<br /> Q_OBJECT

public:<br /> Form(QWidget *parent = 0);

public slots:

void on_lineEdit1_textEdited ( const QString &amp; text );<br /> void on_lineEdit2_textEdited ( const QString &amp; text );<br />};

#endif

form.cpp

<br />#include <QtGui>

#include <iostream>

#include "form.h"

Form::Form(QWidget '''parent)<br /> : QWidget(parent)<br />{<br /> setupUi(this);
<br /> // Limit input to valid values between 0 and 255. Either parent ('this' or 'lineEdit') works, I'm not sure what difference it makes.<br /> QIntValidator''' validator =<br /> //new QIntValidator(0, 255, this->lineEdit);<br /> new QIntValidator(0, 255, this);<br /> this->lineEdit1->setValidator(validator);<br /> this->lineEdit2->setValidator(validator);

}

void Form::on_lineEdit1_textEdited ( const QString &amp; text )<br />{<br /> std::cout << "text1: " << text.toStdString() << std::endl;<br /> std::cout << "number1: " << text.toUInt() << std::endl;<br />}

void Form::on_lineEdit2_textEdited ( const QString &amp; text )<br />{<br /> std::cout << "text2: " << text.toStdString() << std::endl;<br />}

form.ui


<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>Form</class>
<widget class="QWidget" name="Form">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>400</width>
<height>300</height>
</rect>
</property>
<property name="windowTitle">
<string>Form</string>
</property>
<widget class="QLineEdit" name="lineEdit1">
<property name="geometry">
<rect>
<x>250</x>
<y>90</y>
<width>113</width>
<height>27</height>
</rect>
</property>
</widget>
<widget class="QLineEdit" name="lineEdit2">
<property name="geometry">
<rect>
<x>250</x>
<y>170</y>
<width>113</width>
<height>27</height>
</rect>
</property>
</widget>
</widget>
<resources/>
<connections/>
</ui>