事件处理：访问另一个小部件的属性

Question

好吧，这应该很容易。

我试图将drop事件处理到QGraphicsView小部件上。从QTreeView小部件拖动的传入数据。为此，我重新实现了以下方法：

void QGraphicsScene::dragEnterEvent(QGraphicsSceneDragDropEvent *event)
{
    event.accept();
}
void QGraphicsScene::dragMoveEvent(QGraphicsSceneDragDropEvent *event)
{
    event.accept();
}
void QGraphicsScene::dropEvent(QGraphicsSceneDragDropEvent *event)
{
    event.accept();
}

void QGraphicsView::dropEvent(QDropEvent *event)
{
    QPixmap pixmap(event->mimedata()->urls()[0].toString().remove(0,8));
    this.scene()->addPixmap(pixmap);
}

这很好；但是如何在这个小部件的drop事件中更改另一个graphicsview场景呢？即：

void QGraphicsView::dropEvent(QDropEvent *event)
{
    QPixmap pixmap(event->mimedata()->urls()[0].toString().remove(0,8));
    // I cannot access ui; and cannot access my widgets...:
    ui->anotherview->scene()->addPixmap(pixmap);
}

Answer 1

在QGraphicsView中制作一个类似void showPixmap(QPixmap p)的自定义信号，并将其连接到主gui类中的一个插槽，在那里您可以访问ui元素。然后，您可以在dropEvent中调用emit showPixamp(pixmap)。

子类QGraphicsView

//header file
class CustomView : public QGraphicsView 
{
public:
    CustomView(QGraphicsScene*, QWidget*=NULL);
    ~CustomView();
signals:
    void showPixmap(QPixmap p);
protected:
    virtual void dropEvent(QDropEvent *event);
};

//cpp file
CustomView::CustomView(QGraphicsScene *scene, QWidget* parent)
    :QGraphicsView(scene, parent) 
{
    //if you need to initialize variables, etc.
}
void CustomView::dropEvent(QDropEvent *event)
{
    //handle the drop event
    QPixmap mPixmap;
    emit showPixmap(mPixmap);
}

在主GUI类中使用事件过滤器

void GUI::GUI()
{     
    ui->mGraphicsView->installEventFilter(this);
}
bool GUI::eventFilter(QObject *object, QEvent *event)
{
    if (object == ui->mGraphicsView && event->type() == QEvent::DropEnter) {
        QDropEvent *dropEvent = static_cast<QDropEvent*>(event);
        //handle the drop event
        return true;
    }
    else
        return false;
}