Qt實現IP輸入框（模仿Windows系統中的IP輸入框）

本文章所用的代碼整理自https://blog.csdn.net/u011417605/article/details/51353337，感謝原作者分享

本代碼在上述作者代碼基礎上做了如下修改：

（1）屏蔽中文輸入法

（2）修復原作者代碼中輸入框四周的黑色邊線無法正常顯示的問題

（3）添加類似windows的IP輸入框中輸入黑點後自動選中下一區段的特性

（4）修復原作者代碼中讀取的IP字符串沒有添加黑點的問題

主要代碼如下：

#include "qiplineedit.h"
#include <QApplication>
#include <QWidget>
#include <QLabel>

int main(int argc, char *argv[])
{
	QApplication a(argc, argv);
    QWidget w;
    w.resize(300, 150);
    QIPLineEdit *ipEdit=new QIPLineEdit(&w);
    ipEdit->setGeometry(50, 20, 200, 50);
    ipEdit->setText("192.168.11.110");
    QLabel *ipLabel=new QLabel(&w);
    ipLabel->move(50, 90);
    ipLabel->setText(QString("IP is: %1").arg(ipEdit->text()));
    w.show();
	return a.exec();
}

#ifndef QIPLINEEDIT_H
#define QIPLINEEDIT_H

#include <QLineEdit>
#include <QEvent>

class QIPLineEdit : public QLineEdit
{
	Q_OBJECT

public:
	QIPLineEdit(QWidget *parent = 0);
	~QIPLineEdit();

	void setText(const QString &strIP);
	QString text() const;
protected:
	void paintEvent(QPaintEvent *event);
	bool eventFilter(QObject *obj, QEvent *ev);

	int getIndex(QLineEdit *pEdit);
	bool isTextValid(const QString &strIP);
private:
	QLineEdit *m_lineEidt[4];
};

#endif // QIPLINEEDIT_H

#include "qiplineedit.h"
#include <QRegExpValidator>
#include <QPainter>
#include <QHBoxLayout>
#include <QKeyEvent>
#include <QMessageBox>
#include <QDebug>

QIPLineEdit::QIPLineEdit(QWidget *parent)
	: QLineEdit(parent)
{
    QRegExp regx("(2[0-5]{2}|2[0-4][0-9]|1?[0-9]{1,2})"); //只能輸入IP
	QHBoxLayout *pHBox = new QHBoxLayout(this);
	pHBox->setSpacing(10);
    pHBox->setContentsMargins(2, 2, 2, 2);  //不能設置爲全0，否則四周的黑色邊框無法正常顯示
	for (int i = 0; i < 4; i++)
	{
		m_lineEidt[i] = new QLineEdit(this);
		m_lineEidt[i]->setFrame(false);
		m_lineEidt[i]->setMaxLength(3);
		m_lineEidt[i]->setAlignment(Qt::AlignCenter);
		m_lineEidt[i]->installEventFilter(this);
        m_lineEidt[i]->setAttribute(Qt::WA_InputMethodEnabled, false); //屏蔽中文輸入法干擾
        QRegExpValidator *validator = new QRegExpValidator(regx, m_lineEidt[i]);
        m_lineEidt[i]->setValidator(validator);
		m_lineEidt[i]->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Preferred);
		pHBox->addWidget(m_lineEidt[i]);
	}
	this->setReadOnly(true);
}

QIPLineEdit::~QIPLineEdit()
{

}

void QIPLineEdit::paintEvent(QPaintEvent *event)
{
    QLineEdit::paintEvent(event);
	QPainter painter(this);
	QBrush brush;
	brush.setStyle(Qt::BrushStyle::SolidPattern);
	brush.setColor(Qt::black);
	painter.setBrush(brush);

	int width = 0;
	for (int i = 0; i < 3; i++)
	{
		width += m_lineEidt[i]->width() + (i == 0 ? 3 : 10);//佈局的間隔
        painter.drawEllipse(width, height() / 2 - 2, 4, 4);
	}
}

int QIPLineEdit::getIndex(QLineEdit *pEdit)
{
	int index = -1;
	for (int i = 0; i < 4; i++)
	{
		if (pEdit == m_lineEidt[i])
			index = i;
	}
	return index;
}

bool QIPLineEdit::eventFilter(QObject *obj, QEvent *ev)
{
	if (children().contains(obj) && QEvent::KeyPress == ev->type())
	{
		QKeyEvent *keyEvent = dynamic_cast<QKeyEvent *>(ev);
		QLineEdit *pEdit = qobject_cast<QLineEdit *>(obj);
		switch (keyEvent->key())
		{
		case Qt::Key_0:
		case Qt::Key_1:
		case Qt::Key_2:
		case Qt::Key_3:
		case Qt::Key_4:
		case Qt::Key_5:
		case Qt::Key_6:
		case Qt::Key_7:
		case Qt::Key_8:
		case Qt::Key_9:
		{
			QString strText = pEdit->text();
			if (pEdit->selectedText().length())
			{
				pEdit->text().replace(pEdit->selectedText(), QChar(keyEvent->key()));
			}
			else if (strText.length() == 3 || strText.length() < 3 && strText.toInt() * 10 > 255)
			{
				int index = getIndex(pEdit);
				if (index != -1 && index != 3)
				{
					m_lineEidt[index + 1]->setFocus();
					m_lineEidt[index + 1]->selectAll();
				}
			}
			else if (strText.length() == 2 && strText.toInt() * 10 < 255)
			{
				if (Qt::Key_0 == keyEvent->key() && strText.toInt())
				{
					pEdit->setText(strText.insert(pEdit->cursorPosition(), QChar(Qt::Key_0)));
				}
			}
            return QLineEdit::eventFilter(obj, ev);
		}
		break;
		case Qt::Key_Backspace:
		{
			QString strText = pEdit->text();
			if (!strText.length() || strText.length() && !pEdit->cursorPosition())
			{
				int index = getIndex(pEdit);
				if (index != -1 && index != 0)
				{
					m_lineEidt[index - 1]->setFocus();
					int length = m_lineEidt[index - 1]->text().length();
					m_lineEidt[index - 1]->setCursorPosition(length ? length : 0);
				}
			}
            return QLineEdit::eventFilter(obj, ev);
		}
		case Qt::Key_Left:
		{
			if (!pEdit->cursorPosition())
			{
				int index = getIndex(pEdit);
				if (index != -1 && index != 0)
				{
					m_lineEidt[index - 1]->setFocus();
					int length = m_lineEidt[index - 1]->text().length();
					m_lineEidt[index - 1]->setCursorPosition(length ? length : 0);
				}
			}
            return QLineEdit::eventFilter(obj, ev);
		}
		case Qt::Key_Right:
		{
			if (pEdit->cursorPosition() == pEdit->text().length())
			{
				int index = getIndex(pEdit);
				if (index != -1 && index != 3)
				{
					m_lineEidt[index + 1]->setFocus();
					m_lineEidt[index + 1]->setCursorPosition(0);
				}
			}
            return QLineEdit::eventFilter(obj, ev);
		}
        case Qt::Key_Period:  //小數點
        {
            if (pEdit->cursorPosition() == pEdit->text().length())
            {
                int index = getIndex(pEdit);
                if (index != -1 && index != 3)
                {
                    m_lineEidt[index + 1]->setFocus();
                    m_lineEidt[index + 1]->setCursorPosition(0);
                    m_lineEidt[index + 1]->selectAll();
                }
            }
            return QLineEdit::eventFilter(obj, ev);
        }
		default:
			break;
		}
	}
	return false;
}

void QIPLineEdit::setText(const QString &strIP)
{
	if (!isTextValid(strIP))
	{
		return;
	}
	else
	{
		QStringList ipList = strIP.split(".");
        for(int i=0; i<ipList.size(); i++)
        {
            QString ip=ipList.at(i);
            m_lineEidt[i]->setText(ip);
        }
	}
}

bool QIPLineEdit::isTextValid(const QString &strIP)
{
	QRegExp rx2("\\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\b");
	if (!rx2.exactMatch(strIP))
		return false;
	return true;
}

QString QIPLineEdit::text() const
{
	QString strIP;
	for (int i = 0; i < 4; i++)
    {
        if(i>0)
        {
            strIP.append(".");
        }
		strIP.append(m_lineEidt[i]->text());
    }
	return strIP;
}

運行效果：