如何知道一个QLineEdit是否有焦点？ [英] How to know if a QLineEdit got focus?

问题描述

我想知道在 QLineEdit 是否是一个点击。所以我想我应该重新实现以下函数（??）：

I want to be able to know if in the QLineEdit it was a click. So I guess I should reimplement the following function(??):

void QLineEdit::focusInEvent ( QFocusEvent * e )   [virtual protected]

我应该怎么办？

另外，请告诉我如何使用 focusInEvent（）函数，以了解 QLineEdit myEdit;

Also, please tell me how to use focusInEvent() function in order to know if QLineEdit myEdit; object got focus.

EDIT：我写了以下函数：

bool LoginDialog::eventFilter(QObject *target, QEvent *event)
{
    if (target == m_passwordLineEdit)
    {
        if (event->type() == QEvent::FocusIn)
        {
            if(checkCapsLock())
            {
                QMessageBox::about(this,"Caps Lock", "Your caps lock is ON!");

            }
            return true;

        }
    }
    return QDialog::eventFilter(target, event);
}

并已注册 m_passwordLineEdit in LoginDialog 类构造函数，如下所示：

And have registered m_passwordLineEdit in LoginDialog class constructor like this:

m_passwordLineEdit->installEventFilter(this);

它陷入了无限循环的MessageBox-es。请帮我解决这个情况。实际上，我想用一个弹出窗口（不是用 QMessageBox ）来实现这个函数。是否可以使用 QLabel ？

And it's falling into an infinite loop of MessageBox-es. Please help me to resolve this situation. Actually I would like to implemet this function with a pop-up window (not with a QMessageBox). Is it OK to use QLabel for that need?

推荐答案

：

class YourWidget : public QLineEdit
{
    Q_OBJECT

    protected:

    void focusInEvent(QFocusEvent* e);
};

在 .cpp 文件中：

void YourWidget::focusInEvent(QFocusEvent* e)
{
    if (e->reason() == Qt::MouseFocusReason)
    {
      // The mouse trigerred the event
    }

    // You might also call the parent method.
    QLineEdit::focusInEvent(e);
}

您可以找到所有可能原因的列表 。

You can find the list of all possible reasons on this page.

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