QRegExp rx ((2[0-4]//d|25[0-5]|[01]?//d//d?)//.){3}(2[0-4]//d|25[0-4]|[01]?//d//d?) ;

ipLabel = new QLabel(tr("IP Address:"));
    ipLineEdit = new QLineEdit;
    ipLabel->setBuddy(ipLineEdit);

QValidator *validator = new QRegExpValidator(rx, this);
    ipLineEdit->setValidator(validator);
    ipLineEdit->setInputMask("000.000.000.000;");

实现框架下的验证输入的IP、子网掩码的合法性。（生成IP地址类）转自:http://www.qtcn.org/bbs/simple/?t18020.html

//ip.h
#include <qwidget.h>
#include <qstring.h>
#include <qlineedit.h>
#include <qvalidator.h>

#define IP_H

class IP : public QWidget
{
    public:
        IP ( const QString & text, QWidget *parent, const char *name );
        QString getValue();
    private:
        QLineEdit * ip[4];
        QIntValidator * ipv[4];
};

//ip.cpp
#include <qwidget.h>
#include <qlabel.h>
#include <qfont.h>
#include <qhbox.h>
#include <qlineedit.h>

#include "ip.h"

IP::IP(const QString & text, QWidget *parent, const char *nombre) : QWidget(parent, nombre, 0) 
{
    QFont *fuente = new QFont("Arial", 14, QFont::Normal);
    fuente->setPixelSize(14);
    QLabel *label = new QLabel( this );
    label->setFont(* fuente);
    label->setMinimumWidth(140);
    label->setMaximumWidth(140);
    QHBox * ipp = new QHBox((QWidget*) this);
    ipp->setMinimumWidth(140);
    ipp->setMaximumWidth(140);
    for (int i=0; i<4; i++)
    {
        ip = new QLineEdit((QWidget*) ipp, nombre);
        ip->setFont(* fuente);
        ip->setMinimumWidth(30);
        ip->setMaxLength(3);
        ipv = new QIntValidator(0, 255, (QObject*)ipp);
        ip->setValidator(ipv);
    }

label->move(0, 0);
    ipp->move(150, 0);
    label->setText(text);
    // ip->setInputMask("000.000.000.000; ");
}

QString IP::getValue()
{
    bool flag = false;
    for (int i=0; i<4; i++)
        if ( ip->text().isEmpty() )
            flag = true;
    if (flag)
        return QString("0.0.0.0");
    else
        return QString(ip[0]->text()+ "." + ip[1]->text() + "." + ip[2]->text() + "." +
                ip[3]->text());
}

设置具有IP输入格式的输入框模式。转自:http://www.qtcn.org/bbs/simple/?t28473.html

QRegExp rx("((2[0-4]//d|25[0-5]|[01]?//d//d?)//.){3}(2[0-4]//d|25[0-5]|[01]?//d//d?)");
QRegExpValidator v(rx, 0);
QLineEdit le;
le.setValidator(&v);
le.setInputMask("000.000.000.000;0");//只要加上;0保证有默认值即可使得正则和mask同时生效。