自定义QLineEdit,限制n个字符，一个中文相当于两个字符

#ifndef LINEEDIT_H
#define LINEEDIT_H

#include <QWidget>
#include<QLineEdit>

namespace Ui {
class LineEdit;
}
const unsigned DEFAULT_MAXCHARS = 10;
class LineEdit : public QLineEdit
{
    Q_OBJECT

public:
    explicit LineEdit(unsigned maxlen =DEFAULT_MAXCHARS, QWidget *parent = 0);
    void setMaxCharLen(unsigned len);
    ~LineEdit();
private:
    Ui::LineEdit *ui;
    unsigned m_uiLen;
private slots:
    void slotFilter(const QString &text);
};

#endif // LINEEDIT_H


#include "lineedit.h"
#include "ui_lineedit.h"

#include<QDebug>
#include<QRegExp>
#include<QKeyEvent>

LineEdit::LineEdit(unsigned maxlen, QWidget *parent) :
    m_uiLen(maxlen),
    QLineEdit(parent),
    ui(new Ui::LineEdit)
{
    ui->setupUi(this);
    setMaxLength(m_uiLen);
    connect(this,SIGNAL(textEdited(const QString &)),this,SLOT(slotFilter(const QString &)));
}

LineEdit::~LineEdit()
{
    delete ui;
}

void LineEdit::slotFilter(const QString &text)
{
    QString temp = text;
    unsigned num = 0;
    int i = 0;
    for(;i< temp.size();i++)
    {
        if(temp.at(i) >= 0x4e00 && temp.at(i) <= 0x9fa5)
        {
            if(num >= m_uiLen-1) break;
            num += 2;
        }
        else if(num < m_uiLen)
        {
            num += 1;
        }
        else{
            break;
        }
    }
    setText(temp.left(i));
}