仅当鼠标悬停在 QLineEdit 上时，带有 clearbutton 的 qlineedit答案

【问题标题】：qlineedit with clearbutton only when mouse is over the QLineEdit仅当鼠标悬停在 QLineEdit 上时，带有 clearbutton 的 qlineedit
【发布时间】：2015-06-19 11:43:42
【问题描述】：

我想要一个QLineEdit，仅当鼠标悬停在QLineEdit 上时才显示clearbutton（当然该字段不为空）。我已经捕获了分别设置属性的进入和离开事件。这工作正常，但它需要使用鼠标手动初始进入和离开QLineEdit。如何正确启动QLineEdit，使其从一开始就正常工作？尝试模拟最初的鼠标移动并没有得到预期的结果。

cmplLineEdit.h

class cmplLineEdit : public QLineEdit {
    Q_OBJECT

public:
    explicit cmplLineEdit( QWidget* a_par = 0);
    ~cmplLineEdit();

private:
    void enterEvent( QEvent* a_ev);
    void leaveEvent( QEvent* a_ev);
    void enableClearButton( bool a_set, int a_del = 0);

private slots:
    void initialize( void);
};

cmplLineEdit.cpp

cmplLineEdit::cmplLineEdit( QWidget* a_par) : QLineEdit( a_par) {
    m_completeIt = a_cmpl;
    setClearButtonEnabled( false);
    setFocusPolicy( Qt::StrongFocus);
    QTimer::singleShot( 0, this, [=]( void) { initialize(); });
}

cmplLineEdit::~cmplLineEdit() {
}

bool cmplLineEdit::cursorIsInField() {
    return rect().contains(  mapFromGlobal( QCursor::pos()));
}

void cmplLineEdit::initialize( void) {
    QApplication::postEvent( this, new QEvent( ! cursorIsInField() ? QEvent::Enter : QEvent::Leave));
    QApplication::postEvent( this, new QEvent(   cursorIsInField() ? QEvent::Enter : QEvent::Leave));
}

void cmplLineEdit::enableClearButton( bool a_set, int a_del) {
    if( a_del < 0) {
      setClearButtonEnabled( a_set);
    } else
      QTimer::singleShot( a_del, this, [=]( void) { setClearButtonEnabled( a_set); });
}

void cmplLineEdit::enterEvent( QEvent* a_ev) {
    enableClearButton( true, 0);
}

void cmplLineEdit::leaveEvent( QEvent* a_ev) {
    enableClearButton( false, 0);
}

【问题讨论】：

你设置了鼠标跟踪吗？ PS：你应该在你的问题中添加qt标签。

标签： c++ qt qlineedit

【解决方案1】：

是的，鼠标跟踪已开启（否则我将无法获得进入和离开事件）。我重写了代码，自己实现了setClearButtonEnabled()。现在它正在工作。对于任何有兴趣的人：

cmplEdit.h：

#ifndef CMPLLINEEDIT_H
#define CMPLLINEEDIT_H

#include <QWidget>

#include <QLineEdit>
#include <QCompleter>
#include <QAction>

class cmplLineEdit : public QLineEdit {
   Q_OBJECT

public:
   explicit cmplLineEdit( bool a_cmpl = true, QWidget* a_par = 0);
   ~cmplLineEdit();

   static QIcon m_icoOff;
   static QIcon m_icoOn;

private:
   QAction* m_act = nullptr;
   bool m_completeIt = true;
   void enterEvent( QEvent* a_ev);
   void leaveEvent( QEvent* a_ev);
   bool cursorIsInField( void);

private slots:
   void initialize( void);
   void setClearIcon( bool a_set);
   void setClearIcon( const QString& a_txt);
};

#endif // CMPLLINEEDIT_H

cmplEdit.cpp:

#include "cmplLineEdit.h"

#include <QTimer>
#include <QDebug>
#include <QStandardItemModel>
#include <QAbstractItemView>
#include <QEvent>
#include <QApplication>

QIcon cmplLineEdit::m_icoOn;
QIcon cmplLineEdit::m_icoOff;

cmplLineEdit::cmplLineEdit( bool a_cmpl, QWidget* a_par) : QLineEdit( a_par) {
   if( m_icoOn.isNull()) {
      m_icoOn = QIcon( qApp->style()->standardPixmap( QStyle::SP_LineEditClearButton));
   }

   m_completeIt = a_cmpl;
   m_act = addAction( m_icoOn, QLineEdit::ActionPosition::TrailingPosition);
   connect( this, SIGNAL( textChanged( QString)), this, SLOT( setClearIcon( QString)));
   connect( m_act, SIGNAL( triggered( bool)), this, SLOT( clear()));

   QTimer::singleShot( 0, [ this]( void) { initialize(); });
}

cmplLineEdit::~cmplLineEdit() {
}

bool cmplLineEdit::cursorIsInField() {
   return rect().contains( mapFromGlobal( QCursor::pos()));
}

void cmplLineEdit::initialize( void) {
   setClearIcon( cursorIsInField());
}

void cmplLineEdit::enterEvent( QEvent* a_ev) {
   setClearIcon( true);
}

void cmplLineEdit::leaveEvent( QEvent* a_ev) {
   setClearIcon( false);
}

void cmplLineEdit::setClearIcon( bool a_set) {
   if( m_act == nullptr)
      return;

   a_set = a_set && ! text().isEmpty();
   m_act->setIcon( a_set ? m_icoOn : QIcon());
   m_act->setVisible( a_set);
}

void cmplLineEdit::setClearIcon( const QString& a_txt) {
   setClearIcon( ! a_txt.isEmpty());
}

【讨论】：