QGraphicsItem绘制可移动的同心圆弧C++
时间: 2023-11-23 19:06:59 浏览: 59
C++会动的圆
可以通过自定义一个继承自QGraphicsItem的类来实现绘制可移动的同心圆弧。具体实现步骤如下:
1. 在类中添加需要的成员变量,例如圆心坐标、半径、起始角度、结束角度等。
2. 重写boundingRect()函数和paint()函数,boundingRect()函数用于返回图形项的边界矩形,paint()函数用于绘制图形项。在paint()函数中,可以使用QPainter来绘制同心圆弧。
3. 重写mousePressEvent()、mouseMoveEvent()和mouseReleaseEvent()函数,实现鼠标拖动图形项的功能。在mousePressEvent()函数中,记录下鼠标点击时的坐标;在mouseMoveEvent()函数中,计算鼠标移动的距离,更新图形项的位置;在mouseReleaseEvent()函数中,将鼠标点击时的坐标清空。
下面是一个简单的实现示例:
```
#include <QPainter>
#include <QGraphicsItem>
#include <QStyleOptionGraphicsItem>
class ArcItem : public QGraphicsItem
{
public:
ArcItem(qreal x, qreal y, qreal radius, qreal startAngle, qreal endAngle, QGraphicsItem *parent = nullptr)
: QGraphicsItem(parent), m_x(x), m_y(y), m_radius(radius), m_startAngle(startAngle), m_endAngle(endAngle)
{
setFlag(ItemIsMovable);
}
QRectF boundingRect() const override
{
return QRectF(m_x - m_radius, m_y - m_radius, m_radius * 2, m_radius * 2);
}
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override
{
painter->setRenderHint(QPainter::Antialiasing);
QRectF rect(m_x - m_radius, m_y - m_radius, m_radius * 2, m_radius * 2);
painter->drawArc(rect, m_startAngle * 16, (m_endAngle - m_startAngle) * 16);
}
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event) override
{
m_lastPos = event->pos();
}
void mouseMoveEvent(QGraphicsSceneMouseEvent *event) override
{
QPointF delta = event->pos() - m_lastPos;
m_x += delta.x();
m_y += delta.y();
m_lastPos = event->pos();
update();
}
void mouseReleaseEvent(QGraphicsSceneMouseEvent *event) override
{
m_lastPos = QPointF();
}
private:
qreal m_x;
qreal m_y;
qreal m_radius;
qreal m_startAngle;
qreal m_endAngle;
QPointF m_lastPos;
};
```
使用示例:
```
// 创建场景和视图
QGraphicsScene scene;
QGraphicsView view(&scene);
// 创建同心圆弧图形项并添加到场景中
ArcItem *item = new ArcItem(100, 100, 50, 30, 150);
scene.addItem(item);
// 显示视图
view.show();
```
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