Question

在Qt Creator中，我有几个小部件声明如下：

标题文件：

    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.

}

正如您所看到的，我希望再次访问图形场景以更新它，然后重绘它（或其他）。但是我无法访问图形场景，尽管在以不同方式声明小部件的几个小时的试验和错误。

我知道侦听器本身是可行的，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，那么它可以工作，只是我无法访问我已经定义的小部件。 / p>

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

您已将QGraphicsScene传递给MapRender对象的构造函数。你在构造函数中对场景做了什么？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的实施中，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cpp文件中，但我的示例在声明中为了简洁起见。

Answer 2

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();

    //  To add something whenever the user clicks, you don't need the view,
    //  just the scene.
    scene()->addItem( new MyItem() );
}

请记住MapViewer来自QGraphicsView并且视图必须知道它所属的场景 - 所以它有一个scene()方法来返回它，你继承了它。

从类外部访问小部件？

2 个答案: