c++ - 从同类之外访问小部件？

Question

在 Qt Creator 中，我有几个像这样声明的小部件:

头文件:

    class MapViewer : public QGraphicsView
{
    Q_OBJECT

public:
    explicit MapViewer(QGraphicsScene *scene, QWidget *parent = 0);
    ~MapViewer();

public slots:
    void mousePressEvent(QMouseEvent *event);

};

// Declaration for the map editor window.
class MapEditor : public QMainWindow
{
    Q_OBJECT

public:
    explicit MapEditor(QWidget *parent = 0);
    ~MapEditor();

public:
    QLayout *editorLayout;
    QPushButton *btn;
    QGraphicsScene *mapScene;
    MapViewer *mapView;

private:
    Ui::MapEditor *ui;
};

CPP 文件:

  MapEditor::MapEditor(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MapEditor)
{

    ui->setupUi(this);
    this->setWindowTitle("2DXY :: Map Editor");
    this->setGeometry(10,10,1170,750);
    editorLayout = new QVBoxLayout; // Create a new layout
    this->setLayout(editorLayout); // Set the widget's layout to our newly created layout.

    mapScene = new QGraphicsScene(); // Create a new graphics scene to draw upon.

    mapView = new MapViewer(mapScene,this); // Create a new graphics view to display our scene - set its parent to 'this' so that it doesn't open in a new window.
    mapView->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    mapView->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    mapView->setGeometry(20,20,1178,546); // Width first, then height.

和:

void MapViewer::mousePressEvent(QMouseEvent *event)
{
    // Show an empty message box, just to check that the event handler works!
    QMessageBox *notification = new QMessageBox();
    notification->show();
    notification->exec();
    // Some how access the same QGraphicsScene and View (mapScene, mapView) as above, so
    // I can update their contents on the open form / window.

}

如您所见，我希望再次访问图形场景以更新它，然后重绘它(或其他)。但是我根本无法访问图形场景，尽管用不同的方式声明小部件进行了几个小时的反复试验。

我知道监听器本身可以工作，因为如果它设置为打开一个新的消息框，或者输出到调试窗口，那么它就可以工作，只是我无法访问我已经定义的小部件。

我觉得这个问题有一个(相对)简单的解决方案，我只是遗漏了一些明显的东西。

Answer 1

您将 QGraphicsScene 传递给了 MapRender 对象的构造函数。您如何处理其构造函数中的场景？理想情况下，您应该将其存储为 MapRender 的数据成员。例如:

class MapRender {
public:
    MapRender(QGraphicsScene* scene)
      : scene_(scene)
    {
    }

public slots:
    void mousePressEvent(QMouseEvent *event);

private:
    QGraphicsScene* scene_;
}

现在在mousePressEvent 的实现中，您可以访问场景成员:

void MapRender::mousePressEvent(QMouseEvent *event) {
    int CursorX = event->globalX();
    int CursorY = event->globalY();

    QGraphicsRectItem *clickedBox = new QGraphicsRectItem(40,40,32,32);
    clickedBox->setBrush(QBrush(Qt::blue));

    scene_->addItem(clickedBox);
}

请记住，理想情况下，您应该将构造函数的实现放在您的 cpp 文件中，但为简洁起见，我的示例将它放在声明中。