GraphicsView实现添加背景、添加矩形、放缩、移动

最新推荐文章于 2024-07-16 14:29:13 发布

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最新推荐文章于 2024-07-16 14:29:13 发布 · 1.8k 阅读

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#qt #c++

该博文详细介绍了如何使用Qt库实现图形界面元素的交互，包括矩形元素的拖动、缩放和旋转功能。通过GraphicsRectItem、GraphicsScene、GraphicsView和SizeHandleRect等类的定义和实现，展示了鼠标事件处理、画布更新和图形变换等功能。同时，给出了一个主窗口的示例，用于创建和操作矩形，并提供了背景图片设置的接口。

graphicsrectitem.h

#ifndef GRAPHICSRECTITEM_H
#define GRAPHICSRECTITEM_H

#include <QGraphicsItem>
#include "sizehandlerect.h"

class GraphicsRectItem : public QGraphicsItem
{
public:
    GraphicsRectItem(const QRect & rect ,QGraphicsItem * parent);

    QRectF boundingRect() const;
    virtual void resizeTo(SizeHandleRect::Direction dir, const QPointF & point );
    void move(const QPointF & point);
    virtual Qt::CursorShape getCursor(SizeHandleRect::Direction dir );
    SizeHandleRect::Direction  hitTest( const QPointF & point ) const;
    virtual QRectF  rect() const;
    virtual void updateGeometry();
    QRectF m_rect;

private:

    typedef QVector<SizeHandleRect*> Handles;
    Handles m_handles;
    int selection_handle_size = 4;

protected:
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);

    void setState(SelectionHandleState st);
    QVariant itemChange(GraphicsItemChange change, const QVariant &value);
};

#endif // GRAPHICSRECTITEM_H

graphicsscene.h

#ifndef GRAPHICSRECTITEM_H
#define GRAPHICSRECTITEM_H

#include <QGraphicsItem>
#include "sizehandlerect.h"

class GraphicsRectItem : public QGraphicsItem
{
public:
    GraphicsRectItem(const QRect & rect ,QGraphicsItem * parent);

    QRectF boundingRect() const;
    virtual void resizeTo(SizeHandleRect::Direction dir, const QPointF & point );
    void move(const QPointF & point);
    virtual Qt::CursorShape getCursor(SizeHandleRect::Direction dir );
    SizeHandleRect::Direction  hitTest( const QPointF & point ) const;
    virtual QRectF  rect() const;
    virtual void updateGeometry();
    QRectF m_rect;

private:

    typedef QVector<SizeHandleRect*> Handles;
    Handles m_handles;
    int selection_handle_size = 4;

protected:
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);

    void setState(SelectionHandleState st);
    QVariant itemChange(GraphicsItemChange change, const QVariant &value);
};

#endif // GRAPHICSRECTITEM_H

graphicsview.h

#ifndef GRAPHICSVIEW_H
#define GRAPHICSVIEW_H

#include <QGraphicsView>
#include <QKeyEvent>
#include <QWheelEvent>

class GraphicsView : public QGraphicsView
{
    Q_OBJECT

public:
    GraphicsView(QWidget *parent = 0);

protected:
    void keyPressEvent(QKeyEvent *event);
    void wheelEvent(QWheelEvent *event);
};

#endif // GRAPHICSVIEW_H

sizehandlerec.h

#ifndef SIZEHANDLERECT_H
#define SIZEHANDLERECT_H

#include <QGraphicsRectItem>

enum SelectionHandleState { SelectionHandleOff, SelectionHandleInactive, SelectionHandleActive };

class SizeHandleRect : public QGraphicsRectItem
{
public:
    enum Direction { LeftTop , Top, RightTop, Right, RightBottom, Bottom, LeftBottom, Left , Center, None};
    SizeHandleRect(QGraphicsItem* parent , QRectF rect, Direction dir);
    Direction dir() const;
    bool hitTest( const QPointF & point );
    void move(qreal x, qreal y );
    void setState(SelectionHandleState st);
protected:
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
private:
    const Direction m_dir;
    Selecti