Qt 密码框不可选中、复制、粘贴、无右键菜单等

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"));
//QStringLieral是Qt5中新引入的一个用来从“字符串常量”创建QString对象的宏
pCommonLineEdit->setEchoMode(QLineEdit::Password);

下面进行一些设置：不可选择，没有右键菜单

1.可以进行事件重写去完成

class PasswordLineEdit : public QLineEdit
{
    Q_OBJECT

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