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在做用户登录、修改密码的时候，往往会用到密码框，其中一些功能要求与普通的输入框不同。

例如：不能选中、复制、粘贴、无右键菜单等功能，当然设置密码不可见是必须的！

一般的密码框：(默认 可以选中，复制，粘贴，有右键菜单)

QLineEdit *pCommonLineEdit = new QLineEdit(this);pCommonLineEdit->setPlaceholderText(QStringLiteral("密码由字母、数字、下划线组成，长度8-16位"));pCommonLineEdit->setEchoMode(QLineEdit::Password);

1.可以进行事件重写去完成

class PasswordLineEdit : public QLineEdit{    Q_OBJECTpublic:    explicit PasswordLineEdit(QWidget *parent = 0);    ~PasswordLineEdit();protected:    virtual void keyPressEvent(QKeyEvent *event);    virtual void mouseMoveEvent(QMouseEvent *event);    virtual void mouseDoubleClickEvent(QMouseEvent *event);};

PasswordLineEdit::PasswordLineEdit(QWidget *parent)    : QLineEdit(parent){    //设置无右键菜单    setContextMenuPolicy(Qt::NoContextMenu);    //设置无输入时密码提示    setPlaceholderText(QStringLiteral("请输入密码"));    //设置密码隐藏    setEchoMode(QLineEdit::Password);    //设置最大长度16位    setMaxLength(16);}PasswordLineEdit::~PasswordLineEdit(){}//屏蔽输入框全选、复制、粘贴功能void PasswordLineEdit::keyPressEvent(QKeyEvent *event){    if(event->matches(QKeySequence::SelectAll)            || event->matches(QKeySequence::Copy)            || event->matches(QKeySequence::Paste))    {        return;    }    QLineEdit::keyPressEvent(event);}//鼠标位于密码框中时不可移动void PasswordLineEdit::mouseMoveEvent(QMouseEvent *event){    Q_UNUSED(event);}//鼠标位于密码框中时不可移动void PasswordLineEdit::mouseDoubleClickEvent(QMouseEvent *event){    Q_UNUSED(event);}

2.通过事件过滤器去实现上述的功能

QLineEdit *pFilterLineEdit = new QLineEdit(this);pFilterLineEdit->installEventFilter(new EventFilter(this));pFilterLineEdit->setEchoMode(QLineEdit::Password);pFilterLineEdit->setPlaceholderText(QStringLiteral("密码由字母、数字、下划线组成，长度8-16位"));pFilterLineEdit->setContextMenuPolicy(Qt::NoContextMenu);pFilterLineEdit->setMaxLength(16);

class EventFilter : public QObject{public:    explicit EventFilter(QObject *parent = 0);    ~EventFilter();protected:    virtual bool eventFilter(QObject *obj, QEvent *event);};

EventFilter::EventFilter(QObject *parent)    : QObject(parent){}EventFilter::~EventFilter(){}bool EventFilter::eventFilter(QObject *obj, QEvent *event){    QLineEdit *pLineEdit = qobject_cast
   
    (obj);    if (pLineEdit != NULL)    {        switch (event->type())        {        case QEvent::MouseMove:        case QEvent::MouseButtonDblClick:            return true;        case QEvent::KeyPress:        {            QKeyEvent *pKeyEvent = static_cast
    
     (event);            if(pKeyEvent->matches(QKeySequence::SelectAll)                    || pKeyEvent->matches(QKeySequence::Copy)                    || pKeyEvent->matches(QKeySequence::Paste))            {                return true;            }        }        }    }    return QObject::eventFilter(obj, event);}
    
   

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