QStackedWidget不会触发拖放事件

Question

我得到了简单的课程MyStackedWidget，但看起来它没有触发拖放事件 - 我做错了什么？

    #ifndef MYSTACKEDWIDGET_H
    #define MYSTACKEDWIDGET_H

    #include <QStackedWidget>

    class MyStackedWidget : public QStackedWidget
    {
        Q_OBJECT
    public:
        MyStackedWidget();

    signals:
        void dragEnterSignal(QDragEnterEvent *event);
        void dropSignal(QDropEvent *event);
        void dragMoveSignal(QDragMoveEvent *event);
        void dragLeaveSignal(QDragLeaveEvent *event);

    public slots:
        void dragEnterEvent(QDragEnterEvent *event);
        void dropEvent(QDropEvent *event);
        void dragMoveEvent(QDragMoveEvent *event);
        void dragLeaveEvent(QDragLeaveEvent *event);
    };

    #endif // MYSTACKEDWIDGET_H

#include "mystackedwidget.h"
#include <QMimeData>
#include <QDragEnterEvent>

MyStackedWidget::MyStackedWidget()
{
    setMouseTracking(true);
}

void MyStackedWidget::dragEnterEvent(QDragEnterEvent *event)
{
    const QMimeData *mimeData = event->mimeData();

    if(mimeData->hasUrls() && mimeData->urls().size() == 1) {
        event->acceptProposedAction();
    }
    emit dragEnterSignal(event);
}

void MyStackedWidget::dropEvent(QDropEvent *event)
{
    emit dropSignal(event);
}

void MyStackedWidget::dragMoveEvent(QDragMoveEvent *event)
{
    emit dragMoveSignal(event);
}

void MyStackedWidget::dragLeaveEvent(QDragLeaveEvent *event)
{
    emit dragLeaveSignal(event);
}