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 &lt;QApplication&amp;gt;

#include &quot;form.h&amp;quot;

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

form.show();<br /> return app.exec&amp;amp;#40;&amp;#41;;<br />}<br />

form.h

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

#include &quot;ui_form.h&amp;quot;

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 &lt;QtGui&amp;gt;

#include &lt;iostream&amp;gt;

#include &quot;form.h&amp;quot;

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-&gt;lineEdit);<br /> new QIntValidator(0, 255, this);<br /> this-&gt;lineEdit1-&gt;setValidator(validator);<br /> this-&gt;lineEdit2-&gt;setValidator(validator);

}

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

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

form.ui


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