Arc在QGraphicsScene [英] Arc in QGraphicsScene
问题描述
我想在QGraphicsScene中实现arc。我希望在点击三点时，我的弧应该被绘制，使得在点击三点时，绘制弧，其中第一点将是弧的起点，第二点是弧上的任何点，第三点是弧的终点。我已经尝试了drawArc函数，但混淆了startangle和spanangle。我无法动态设置它们。请建议我一些方法继续。
I want to implement arc in QGraphicsScene. I want that on clicking of three points my arc should be drawn such that on clicking of three points arc is drawn where first point will be starting of arc, second will be any point on arc and third will be end point of arc. I have tried studing drawArc function but got confused with startangle and spanangle. I was unable to set them dynamically. Please suggest me some way to proceed.
我尝试将该解决方案引入我的项目，但出现以下错误：
I tried the solution to embend it in my project but got the following error:
error: cannot allocate an object of abstract type 'arc'
arcItem = new arc(++id, startP, midP, endP);
你能帮我解决问题。我给我的项目的一部分代码。
在cadgraphicsscene的mousepress事件我做了以下事情。
Can you please help me out to solve the problem. I am giving a part of code to my project. In mousepress event of cadgraphicsscene I have done following thing.
cadgraphicsscene.cpp
cadgraphicsscene.cpp
void CadGraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
// mousePressEvent in the graphicsScene
if(mouseEvent->button() == Qt::LeftButton)
{
switch (entityMode)
{
case ArcMode:
if (mFirstClick)
{
startP = mouseEvent->scenePos();
mFirstClick = false;
mSecondClick = true;
}
else if (!mFirstClick && mSecondClick)
{
midP = mouseEvent->scenePos();
mFirstClick = false;
mSecondClick = false;
mThirdClick = true;
}
else if (!mSecondClick && mThirdClick)
{
endP = mouseEvent->scenePos();
mThirdClick = false;
mPaintFlag = true;
}
if (mPaintFlag)
{
arcItem = new arc(++id, startP, midP, endP);
itemList.append(arcItem);
mUndoStack->push(new CadCommandAdd(this, arcItem));
setFlags();
}
}
}
}
arc .cpp
#include "arc.h"
arc::arc(int i, QPointF point1, QPointF point2, QPointF point3)
{
// assigns id
id = i;
p1 = point1;
p2 = point2;
p3 = point3;
lineBC(point2, point3);
lineAC(point1, point3);
lineBA(point2, point1);
rad = qAbs(lineBC.length()/(2*qSin(qDegreesToRadians(lineAC.angleTo(lineBA)))));
bisectorBC(lineBC.pointAt(0.5), lineBC.p2());
bisectorBC.setAngle(lineBC.normalVector().angle());
bisectorBA(lineBA.pointAt(0.5), lineBA.p2());
bisectorBA.setAngle(lineBA.normalVector().angle());
bisectorBA.intersect(bisectorBC, ¢er);
ellipse = new QGraphicsEllipseItem(center.x() - rad, center.y() - rad, rad*2, rad*2);
lineOA(center, point1);
lineOC(center, point3);
}
arc::arc(int i, QLineF start, QLineF end)
{
// assigns id
id = i;
lineOA.angle() = start;
lineOC.angle() - lineOA.angle() = end;
}
int arc::type() const
{
// Enable the use of qgraphicsitem_cast with arc item.
return Type;
}
void arc::paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
QWidget *widget)
{
QPen paintpen;
painter->setRenderHint(QPainter::Antialiasing);
paintpen.setWidth(1);
if (isSelected())
{
// sets brush for end points
painter->setBrush(Qt::SolidPattern);
paintpen.setColor(Qt::red);
painter->setPen(paintpen);
paintpen.setStyle(Qt::DashLine);
paintpen.setColor(Qt::black);
painter->setPen(paintpen);
painter->drawArc(ellipse->boundingRect(),lineOA.angle(),lineOC.angle() - lineOA.angle());
}
else
{
painter->setBrush(Qt::SolidPattern);
paintpen.setColor(Qt::black);
painter->setPen(paintpen);
painter->drawArc(ellipse->boundingRect(),lineOA.angle(),lineOC.angle() - lineOA.angle());
}
}
arc.h
include <QGraphicsItem>
#include "qmath.h"
class arc : public QObject, public QGraphicsItem
{
Q_OBJECT
public:
arc(int, QPointF, QPointF, QPointF);
arc(int, QLineF, QLineF);
virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
QWidget *widget);
enum { Type = UserType + 6 };
int type() const;
int id;
QPointF startP, midP, endP, p1, p2, p3,center;
QLineF lineBC;
QLineF lineAC;
QLineF lineBA;
QLineF lineOA;
QLineF lineOC;
QLineF bisectorBC;
QLineF bisectorBA;
QGraphicsEllipseItem *ellipse;
qreal rad;
private:
QVector<QPointF> stuff;
};
#endif // ARC_H
请帮我解决错误。
推荐答案
QGraphicsItem的子类，它需要3个点，并且与圆的圆弧相交。第二点总是在中间。 （可选择性和其他属性尚未完全实现或测试）。
A Subclass of QGraphicsItem, that takes 3 points, and intersects the three with an arc of a circle. The second point is always in the middle. (Selectablity and other properties haven't been fully implemented or tested).
注意：Qt Creator包含更多高级子类 QGraphicsItem 如碰撞小鼠和40,000个芯片示例。
Note: Qt Creator includes more advanced examples of subclassed QGraphicsItems such as Colliding Mice, and 40,000 chips examples.
http://qt-project.org/doc/qt-5/examples-graphicsview.html
还要从 QGraphicsItem 启用 QObject 信号和插槽和属性，您应该使用 QGraphicsObject 。
Also to enable QObject signals and slots and properties from a QGraphicsItem, you should use QGraphicsObject.
注意：添加到github上此处。
Note: added onto github here.
arcgraphicsitem.h
arcgraphicsitem.h
#ifndef ARCGRAPHICSITEM_H
#define ARCGRAPHICSITEM_H
#include <QGraphicsItem>
#include <QLineF>
#include <QPointF>
#include <QPainter>
#include <QStyleOptionGraphicsItem>
#include <QWidget>
class ArcGraphicsItem : public QGraphicsItem
{
public:
ArcGraphicsItem();
ArcGraphicsItem(int i, QPointF point0, QPointF point1, QPointF point2);
~ArcGraphicsItem();
QRectF boundingRect() const;
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
int type() const { return Type;}
int id() {return m_id;}
QPainterPath shape() const;
protected:
private:
void init();
enum { Type = UserType + 6 };
int m_id;
QPointF startP, midP, endP, p1, p2, p3, center;
QLineF lineBC;
QLineF lineAC;
QLineF lineBA;
QLineF lineOA;
QLineF lineOB;
QLineF lineOC;
QLineF bisectorBC;
QLineF bisectorBA;
qreal startAngle;
qreal spanAngle;
QRectF circle;
QRectF boundingRectTemp;
qreal rad;
};
#endif // ARCGRAPHICSITEM_H
arcgraphicsitem.cpp
arcgraphicsitem.cpp
#include "arcgraphicsitem.h"
#include "qmath.h"
#include <QPen>
#include <QDebug>
#include <QPainterPath>
ArcGraphicsItem::ArcGraphicsItem(int i,
QPointF point1,
QPointF point2,
QPointF point3)
: m_id(i), p1(point1), p2(point2), p3(point3)
{
init();
}
ArcGraphicsItem::ArcGraphicsItem()
{
p1 = QPointF(0,0);
p2 = QPointF(0,1);
p3 = QPointF(1,1);
m_id = -1;
init();
}
ArcGraphicsItem::~ArcGraphicsItem()
{
}
void ArcGraphicsItem::init()
{
lineBC = QLineF(p2, p3);
lineAC = QLineF(p1, p3);
lineBA = QLineF(p2, p1);
rad = qAbs(lineBC.length()/(2*qSin(qDegreesToRadians(lineAC.angleTo(lineBA)))));
bisectorBC = QLineF(lineBC.pointAt(0.5), lineBC.p2());
bisectorBC.setAngle(lineBC.normalVector().angle());
bisectorBA = QLineF(lineBA.pointAt(0.5), lineBA.p2());
bisectorBA.setAngle(lineBA.normalVector().angle());
bisectorBA.intersect(bisectorBC, ¢er);
circle = QRectF(center.x() - rad, center.y() - rad, rad*2, rad*2);
lineOA = QLineF(center, p1);
lineOB = QLineF(center, p2);
lineOC = QLineF(center, p3);
startAngle = lineOA.angle();
spanAngle = lineOA.angleTo(lineOC);
// Make sure that the span angle covers all three points with the second point in the middle
if(qAbs(spanAngle) < qAbs(lineOA.angleTo(lineOB)) || qAbs(spanAngle) < qAbs(lineOB.angleTo(lineOC)))
{
// swap the end point and invert the spanAngle
startAngle = lineOC.angle();
spanAngle = 360 - spanAngle;
}
int w = 10;
boundingRectTemp = circle.adjusted(-w, -w, w, w);
}
QRectF ArcGraphicsItem::boundingRect() const
{
// outer most edges
return boundingRectTemp;
}
void ArcGraphicsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
QPen paintpen;
painter->setRenderHint(QPainter::Antialiasing);
paintpen.setWidth(1);
// Draw arc
if(isSelected())
{
painter->setBrush(Qt::SolidPattern);
paintpen.setColor(Qt::black);
painter->setPen(paintpen);
}
else
{
paintpen.setStyle(Qt::DashLine);
paintpen.setColor(Qt::black);
painter->setPen(paintpen);
}
QPainterPath path;
path.arcMoveTo(circle,startAngle);
path.arcTo(circle, startAngle, spanAngle);
// Draw points
if (isSelected())
{
// sets brush for end points
painter->setBrush(Qt::SolidPattern);
paintpen.setColor(Qt::red);
painter->setPen(paintpen);
qreal ptRad = 10;
painter->drawEllipse(p1, ptRad, ptRad);
painter->drawEllipse(p2, ptRad, ptRad);
painter->drawEllipse(p3, ptRad, ptRad);
}
painter->setBrush(Qt::NoBrush);
painter->drawPath(path);
}
QPainterPath ArcGraphicsItem::shape() const
{
QPainterPath path;
path.arcMoveTo(circle,startAngle);
path.arcTo(circle, startAngle, spanAngle);
return path;
}
希望有助于
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