Qt实现密码显示按钮

#ifndef PASSWORDLINEEDIT_H
#define PASSWORDLINEEDIT_H

#include <QAction>
#include <QLineEdit>
#include <QToolButton>

class PasswordLineEdit : public QLineEdit {
public:
  PasswordLineEdit(QWidget *parent = nullptr);
private slots:
  void onPressed();
  void onReleased();

protected:
  void enterEvent(QEvent *event);
  void leaveEvent(QEvent *event);
  void focusInEvent(QFocusEvent *event);
  void focusOutEvent(QFocusEvent *event);

private:
  QToolButton *button;
};

#endif // PASSWORDLINEEDIT_H

#include "passwordlineedit.h"

PasswordLineEdit::PasswordLineEdit(QWidget *parent) : QLineEdit(parent)
{
    setEchoMode(QLineEdit::Password);
    QAction *action = addAction(QIcon(":/eyeOff"), QLineEdit::TrailingPosition);
    button = qobject_cast<QToolButton *>(action->associatedWidgets().last());
    button->hide();
    button->setCursor(QCursor(Qt::PointingHandCursor));
    connect(button, &QToolButton::pressed, this, &PasswordLineEdit::onPressed);
    connect(button, &QToolButton::released, this, &PasswordLineEdit::onReleased);
}

void PasswordLineEdit::onPressed()
{
    QToolButton *button = qobject_cast<QToolButton *>(sender());
    button->setIcon(QIcon(":/eyeOn"));
    setEchoMode(QLineEdit::Normal);
}

void PasswordLineEdit::onReleased()
{
    QToolButton *button = qobject_cast<QToolButton *>(sender());
    button->setIcon(QIcon(":/eyeOff"));
    setEchoMode(QLineEdit::Password);
}

void PasswordLineEdit::enterEvent(QEvent *event)
{
    button->show();
    QLineEdit::enterEvent(event);
}

void PasswordLineEdit::leaveEvent(QEvent *event)
{
    button->hide();
    QLineEdit::leaveEvent(event);
}

void PasswordLineEdit::focusInEvent(QFocusEvent *event)
{
    button->show();
    QLineEdit::focusInEvent(event);
}

void PasswordLineEdit::focusOutEvent(QFocusEvent *event)
{
    button->hide();
    QLineEdit::focusOutEvent(event);
}

#include "passwordlineedit.h"

#include <QApplication>
#include <QFormLayout>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget w;
    PasswordLineEdit *w1 = new PasswordLineEdit;
    QLineEdit *w2 = new QLineEdit;
    QFormLayout *lay = new QFormLayout(&w);
    lay->addRow("PasswordLineEdit: ", w1);
    lay->addRow("QLineEdit: ", w2);
    w.show();

    return a.exec();
}