【QT源代码复用】模拟QCompleter的弹窗方式

#ifndef LDS_LINEEDIT_COMPLETER_H
#define LDS_LINEEDIT_COMPLETER_H

#include <QLineEdit>

class lds_lineedit_completer_inter;
class lds_lineedit_completer : public QLineEdit
{
    Q_OBJECT
public:
    explicit lds_lineedit_completer(QWidget *parent = nullptr);

    void setCompleterTop(QWidget *popup);

private:
    lds_lineedit_completer_inter *obj;
};

class lds_lineedit_completer_inter : public QObject{
    Q_OBJECT
public:
    explicit lds_lineedit_completer_inter(QObject *parent = nullptr);

    ~lds_lineedit_completer_inter();

    void setPopup(QWidget *popup, QLineEdit *widget);
protected:
    bool eventFilter(QObject *o, QEvent *e);
private:
    void showPopup();
private:
    QWidget *popup;
    QLineEdit *widget;
    bool eatFocusOut = false;
};

#endif // LDS_LINEEDIT_COMPLETER_H

#include "lds_lineedit_completer.h"
#include <QEvent>
#include <QKeyEvent>

lds_lineedit_completer::lds_lineedit_completer(QWidget *parent) : QLineEdit(parent)
{
    obj = new lds_lineedit_completer_inter(this);
}

void lds_lineedit_completer::setCompleterTop(QWidget *popup)
{
    obj->setPopup(popup, this);
}

lds_lineedit_completer_inter::lds_lineedit_completer_inter(QObject *parent)
    : QObject(parent)
{

}

lds_lineedit_completer_inter::~lds_lineedit_completer_inter()
{
    delete popup;
}

void lds_lineedit_completer_inter::setPopup(QWidget *popup, QLineEdit *widget)
{
    this->popup = popup;
    this->widget = widget;

    widget->installEventFilter(this);
    popup->installEventFilter(this);

    Qt::FocusPolicy origPolicy = widget->focusPolicy();
    popup->setParent(nullptr, Qt::Popup);
    popup->setFocusPolicy(Qt::NoFocus);
    popup->setFocusProxy(widget);
    widget->setFocusPolicy(origPolicy);

}

bool lds_lineedit_completer_inter::eventFilter(QObject *o, QEvent *e)
{
    if(eatFocusOut && o == widget && e->type() == QEvent::FocusOut) {
        if (popup && popup->isVisible())
            return true;
    }

    switch (e->type()) {
    case QEvent::KeyPress :{
        QKeyEvent *ke = static_cast<QKeyEvent *>(e);
        const int key = ke->key();
        switch (key) {
        case Qt::Key_End:
        case Qt::Key_Home:
        case Qt::Key_Up:
        case Qt::Key_Down:
        case Qt::Key_PageUp:
        case Qt::Key_PageDown:
            return false;
        case Qt::Key_F4:
            if (ke->modifiers() & Qt::AltModifier)
                popup->hide();
            return false;
        case Qt::Key_Backtab:
        case Qt::Key_Escape:
            popup->hide();
            return false;
        }
        if(!popup->isVisible()) {
            showPopup();
        }
        
        if(o != widget) {
                eatFocusOut = false;
                (static_cast<QObject *>(widget))->event(ke);
                eatFocusOut = true;
        }
        break;
    }
    case QEvent::MouseButtonPress: {
        if (!popup->underMouse()) {
            popup->hide();
        }
        break;
    }
    case QEvent::InputMethod:
    case QEvent::ShortcutOverride:
        //            QApplication::sendEvent(widget, e);
        return false;

    default:
        return false;
    }
    return false;
}

void lds_lineedit_completer_inter::showPopup()
{
    popup->move(widget->mapToGlobal(QPoint(0, 0)) - QPoint(0, popup->height()));
    popup->show();
}