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自定义实体的创建和使用

自定义实体被视为高阶CAD二次开发的象征，很多招聘信息上都明确标注“熟悉自定义实体开发者优先”的字样，其重要性可见一斑！

一直以来，CAD二次开发的主要工作就是通过程序在模型空间绘制各种基本图元，从而实现辅助成图。在这种情况下，即使在业务上密切相关的图元，其在图纸上也是离散的，开发者和用户无法将其视为一个整体进行绘制或调整，封装性仅仅体现在绘图函数这一等级。

如果将这些密切相关的图元形成一个逻辑整体（即自定义实体），有什么好处呢？①可以实现更有意义的封装：无论绘图逻辑多么复杂，它永远被封装在自定义实体内部，调用者只需要向其传递关键数据就能驱动图形绘制和变化，这就是典型的”高内聚低耦合“；②增加用户交互性：自定义实体可以暴露操作接口给用户，用户可以更加灵活地调整图形；③规范业务逻辑：自定义实体的制定过程就是业务分解的过程。在我看来，自定义实体不只是一种技术，更是一种思维。

本文先介绍如何创建并使用自定义实体，在学习自定义实体的过程中，你将领略到AutoCAD系统的博大精深！

下一篇文章将讲解如何使用CLI技术封装自定义实体供.NET项目使用，这在大型CAD插件系统中非常实用，敬请期待！

自定义实体创建

使用ObjectARX向导创建自定义实体的项目模板比较方便，主要步骤如下：

  • 创建ObjectDBX项目

  • 添加COM支持，为后续COM封装做准备

  • 添加自定义实体

接下来的主要工作就是实现自定义实体CustomEntity1的代码逻辑。

自定义实体的实现起始非常简单，就是创建一个继承自AcDbEntity的子类，然后实现父类的各种虚函数，其中每个虚函数都有其特定含义，也对应着在CAD软件中的某项操作。通俗来说，这些虚函数实现得越多，自定义实体的功能就越完善、越强大。

  • 头文件
    • 只包含一个无参构造函数，否则出错，可以在无参构造函数中定义各参数的默认值，另外定义一个set方法用于显示设置各属性值。
    • 在设计自定义实体时，如何确定基本绘图数据将是一项具有挑战性和富有意义的工作！这里定义了四个属性：R1、R2、N、center。
    • 在自定义实体中定义获取/修改属性的成员方法，这样可以保证图形随着属性的变化而变化。这里定义了八个成员方法：getCenter/SetCenter、getR1/setR1、getR2/setR2、getN/setN。
    • 重写父类的八个虚函数，这里是自定义实体的逻辑核心，每个虚函数对应一个功能，详见源文件解释。
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#pragma once
#ifdef MYCUSTOMENTITY_MODULE
#define DLLIMPEXP __declspec(dllexport)
#else
#define DLLIMPEXP
#endif
#include "dbmain.h"

class DLLIMPEXP CustomEntity1 : public AcDbEntity {
public:
	ACRX_DECLARE_MEMBERS(CustomEntity1) ;

protected:
	static Adesk::UInt32 kCurrentVersionNumber ;
    
private:
	// 大圆半径
	double R1;
	// 小圆半径
	double R2;
	// 环向等分数
	int N;
	// 大圆圆心坐标
	AcGePoint3d center;

public:
	CustomEntity1 () ;
	virtual ~CustomEntity1 () ;
	void set(AcGePoint3d center, double R1 = 1000, double R2 = 50, int N = 8);
    	const AcGePoint3d& getCenter() const {
		return center;
	}
    
	Acad::ErrorStatus getCenter(AcGePoint3d& point) const {
		assertReadEnabled();
		point = center;
		return Acad::eOk;
	}

	Acad::ErrorStatus setCenter(const AcGePoint3d& point) {
		assertWriteEnabled();
		center = point;
		return Acad::eOk;
	}

	Acad::ErrorStatus getR1(double &d) const {
		assertReadEnabled();
		d = R1;
		return Acad::eOk;
	}
	Acad::ErrorStatus setR1(double d) {
		assertWriteEnabled();
		R1 = d;
		return Acad::eOk;
	}

	Acad::ErrorStatus getR2(double &d) const {
		assertReadEnabled();
		d = R2;
		return Acad::eOk;
	}
	Acad::ErrorStatus setR2(double d) {
		assertWriteEnabled();
		R2 = d;
		return Acad::eOk;
	}

	Acad::ErrorStatus getN(int &i) const {
		assertReadEnabled();
		i = N;
		return Acad::eOk;
	}
	Acad::ErrorStatus setN(int i) {
		assertWriteEnabled();
		N = i;
		return Acad::eOk;
	}
    
public:
	virtual Acad::ErrorStatus dwgOutFields (AcDbDwgFiler *pFiler) const ;
	virtual Acad::ErrorStatus dwgInFields (AcDbDwgFiler *pFiler) ;
protected:
	virtual Adesk::Boolean subWorldDraw (AcGiWorldDraw *mode) ;
	virtual Adesk::Boolean subWorldDraw(AcGiWorldDraw* mode);
	virtual Acad::ErrorStatus subGetGeomExtents(AcDbExtents& extents) const;
	virtual Acad::ErrorStatus subTransformBy(const AcGeMatrix3d& xform);
	virtual Acad::ErrorStatus subGetGripPoints(AcGePoint3dArray& gripPoints, AcDbIntArray& osnapModes, AcDbIntArray& geomIds) const;
	virtual Acad::ErrorStatus subMoveGripPointsAt(const AcDbIntArray& indices, const AcGeVector3d& offset);
	virtual Acad::ErrorStatus subExplode(AcDbVoidPtrArray& entitySet) const;
} ;

#ifdef MYCUSTOMENTITY_MODULE
ACDB_REGISTER_OBJECT_ENTRY_AUTO(CustomEntity1)
#endif
  • 源文件
    • dwgOutFields：自定义实体各属性的序列化逻辑。
    • dwgInFields：自定义实体各属性的反序列化逻辑。
    • subWorldDraw：自定义实体的绘制逻辑，根据属性绘图，在这里可以用mode->geometry()绘制基本图形，也可以定义其他已有实体，调用该实体的worldDraw()方法。
    • subGetGeomExtents：自定义实体的包围盒计算逻辑。
    • subTransformBy：自定义实体的图形变换逻辑。
    • subGetGripPoints：定义自定义实体的夹点。
    • subMoveGripPointsAt：自定义实体夹点拖动的逻辑。
    • subExplode：自定义实体炸开逻辑。
    • 还有很多其他虚函数，逐步探究！
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#include "StdAfx.h"
#include "CustomEntity1.h"

const double PI = 3.1415926;
Adesk::UInt32 CustomEntity1::kCurrentVersionNumber =1 ;

ACRX_DXF_DEFINE_MEMBERS (
	CustomEntity1, AcDbEntity,
	AcDb::kDHL_CURRENT, AcDb::kMReleaseCurrent, 
	AcDbProxyEntity::kNoOperation, USTOMENTITY1,
LHMYCUSTOMENTITYAPP
|Product Desc:     A description for your object
|Company:          Your company name
|WEB Address:      Your company WEB site address
)

CustomEntity1::CustomEntity1 () : AcDbEntity () {
	this->center = AcGePoint3d(0, 0, 0);
	this->R1 = 1000;
	this->R2 = 50;
	this->N = 8;
}

CustomEntity1::~CustomEntity1 () {}

void CustomEntity1::set(AcGePoint3d center, double R1, double R2, int N){
	this->center = center;
	this->R1 = R1;
	this->R2 = R2;
	this->N = N;
}

Acad::ErrorStatus CustomEntity1::dwgOutFields (AcDbDwgFiler *pFiler) const {
	assertReadEnabled();
	//----- Save parent class information first.
	Acad::ErrorStatus es = AcDbEntity::dwgOutFields(pFiler);
	if (es != Acad::eOk)
		return (es);
	//----- Object version number needs to be saved first
	if ((es = pFiler->writeUInt32(CustomEntity1::kCurrentVersionNumber)) != Acad::eOk)
		return (es);
	//----- Output params
	es = pFiler->writeDouble(R1);
	if (Acad::eOk != es) return es;
	es = pFiler->writeDouble(R2);
	if (Acad::eOk != es) return es;
	es = pFiler->writeInt32(N);
	if (Acad::eOk != es) return es;
	es = pFiler->writePoint3d(center);
	if (Acad::eOk != es) return es;
	return (pFiler->filerStatus());
}

Acad::ErrorStatus CustomEntity1::dwgInFields (AcDbDwgFiler *pFiler) {
	assertWriteEnabled();
	//----- Read parent class information first.
	Acad::ErrorStatus es = AcDbEntity::dwgInFields(pFiler);
	if (es != Acad::eOk)
		return (es);
	//----- Object version number needs to be read first
	Adesk::UInt32 version = 0;
	if ((es = pFiler->readUInt32(&version)) != Acad::eOk)
		return (es);
	if (version > CustomEntity1::kCurrentVersionNumber)
		return (Acad::eMakeMeProxy);
	//----- Read params
	es = pFiler->readDouble(&R1);
	if (Acad::eOk != es) return es;
	es = pFiler->readDouble(&R2);
	if (Acad::eOk != es) return es;
	es = pFiler->readInt32(&N);
	if (Acad::eOk != es) return es;
	es = pFiler->readPoint3d(&center);
	if (Acad::eOk != es) return es;
	return (pFiler->filerStatus());
}

Adesk::Boolean CustomEntity1::subWorldDraw (AcGiWorldDraw *mode) {
	assertReadEnabled();
	mode->geometry().circle(center, R1, AcGeVector3d(0, 0, 1));
	for (int i = 0; i < N; i++)
	{
		double x1 = center.x + R1 * cos(2 * PI / N * i);
		double y1 = center.y + R1 * sin(2 * PI / N * i);
		mode->geometry().circle(AcGePoint3d(x1, y1, 0), R2, AcGeVector3d(0, 0, 1));
	}
	AcDbText* text = new AcDbText();
	text->setPosition(center);
	text->setTextString(L"测试");
	text->setHeight(R1 / 10);
	text->setColorIndex(1);
	text->worldDraw(mode);
	return Adesk::kTrue;
}

Acad::ErrorStatus CustomEntity1::subGetGeomExtents(AcDbExtents& extents) const
{
	assertReadEnabled();
	for (int i = 0; i < N; i++)
	{
		double x1 = center.x + R1 * cos(2 * PI / N * i);
		double y1 = center.y + R1 * sin(2 * PI / N * i);
		extents.addPoint(AcGePoint3d(x1 + R2, y1 + R2, 0));
		extents.addPoint(AcGePoint3d(x1 + R2, y1 - R2, 0));
		extents.addPoint(AcGePoint3d(x1 - R2, y1 + R2, 0));
		extents.addPoint(AcGePoint3d(x1 - R2, y1 - R2, 0));
	}
	AcDbText* text = new AcDbText();
	text->setPosition(center);
	text->setTextString(L"测试");
	text->setHeight(R1 / 10);
	text->setColorIndex(1);
	AcDbExtents ext;
	text->getGeomExtents(ext);
	extents.addExt(ext);
	return Acad::eOk;
}

Acad::ErrorStatus CustomEntity1::subTransformBy(const AcGeMatrix3d& xform)
{
	assertWriteEnabled();
	center.transformBy(xform);
	double scale = xform.scale();
	R1 *= scale;
	R2 *= scale;
	return Acad::eOk;
}

Acad::ErrorStatus CustomEntity1::subGetGripPoints(AcGePoint3dArray& gripPoints, AcDbIntArray& osnapModes, AcDbIntArray& geomIds) const
{
	assertReadEnabled();
	gripPoints.append(center);
	return Acad::eOk;
}

Acad::ErrorStatus CustomEntity1::subMoveGripPointsAt(const AcDbIntArray& indices, const AcGeVector3d& offset)
{
	assertWriteEnabled();
	for (int i = 0; i < indices.length(); i++)
	{
		switch (indices[i])
		{
		case 0:
			center += offset;
			break;
		}
	}
	return Acad::eOk;
}

Acad::ErrorStatus CustomEntity1::subExplode(AcDbVoidPtrArray& entitySet) const
{
	assertReadEnabled();
	AcDbCircle* circle = new AcDbCircle(center, AcGeVector3d(0, 0, 1), R1);
	entitySet.append(circle);
	for (int i = 0; i < N; i++)
	{
		double x1 = center.x + R1 * cos(2 * PI / N * i);
		double y1 = center.y + R1 * sin(2 * PI / N * i);
		AcDbCircle* subCircle = new AcDbCircle(AcGePoint3d(x1, y1, 0), AcGeVector3d(0, 0, 1), R2);
		entitySet.append(subCircle);
	}
	AcDbText* text = new AcDbText();
	text->setPosition(center);
	text->setTextString(L"测试");
	text->setHeight(R1 / 10);
	text->setColorIndex(1);
	entitySet.append(text);
	return Acad::eOk;
}

  • 导出文件

    • 在On_kInitAppMsg()中添加以下代码：
    1
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    CustomEntity1::rxInit();
    acrxBuildClassHierarchy();
    • 在On_kUnloadAppMsg()中添加以下代码：
    1
    deleteAcRxClass(CustomEntity1::desc());

将自定义实体添加至模型空间

  • 定义一个命令向模型空间添加自定义实体（该过程与添加内置图元别无二致）：
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static void LHMyGroupMyCommand() {
	AcDbDatabase* pDB = acdbHostApplicationServices()->workingDatabase();
    
	AcDbBlockTable* pBlockTable;
	pDB->getSymbolTable(pBlockTable, AcDb::kForWrite);
	AcDbBlockTableRecord* pBlockTableRecord;
	pBlockTable->getAt(ACDB_MODEL_SPACE, pBlockTableRecord, AcDb::kForWrite);

	CustomEntity1* ent = new CustomEntity1();
	pBlockTableRecord->appendAcDbEntity(ent);

	CustomEntity1* ent2 = new CustomEntity1();
	ent2->set(AcGePoint3d(500, 500, 0), 500, 30, 14);
	pBlockTableRecord->appendAcDbEntity(ent2);

	ent->close();
	ent2->close();
	pBlockTableRecord->close();
	pBlockTable->close();
}

  • 定义一个命令获取选中自定义实体的包围盒：
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static void LHMyGroupMyCommand2() {
	AcDbDatabase* pDB = acdbHostApplicationServices()->workingDatabase();
	ads_name ss;
	acedSSGet(nullptr, nullptr, nullptr, nullptr, ss);
	Adesk::Int32 len;
	acedSSLength(ss, &len);
	AcDbObjectId id;
	for (Adesk::Int32 i = 0; i < len; i++)
	{
		ads_name ent;
		acedSSName(ss, i, ent);
		acdbGetObjectId(id, ent);
	}
	AcDbEntity* pEnt;
	acdbOpenObject(pEnt, id);
	if (pEnt != nullptr) {
		AcDbExtents ext;
		pEnt->getGeomExtents(ext);
        // 使用完成之后一定要关闭实体
        pEnt->close();
		acutPrintf(L"x1=%.3f,y1=%.3f,x2=%.3f,y2=%.3f", ext.minPoint().x, ext.minPoint().y, ext.maxPoint().x, ext.maxPoint().y);
	}
}

  • 定义一个命令用于修改圆心坐标：
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static void LHMyGroupMyCommand3() {
	AcDbDatabase* pDB = acdbHostApplicationServices()->workingDatabase();
	ads_name ss;
	acedSSGet(nullptr, nullptr, nullptr, nullptr, ss);
	Adesk::Int32 len;
	acedSSLength(ss, &len);
	AcDbObjectId id;
	for (Adesk::Int32 i = 0; i < len; i++)
	{
		ads_name ent;
		acedSSName(ss, i, ent);
		acdbGetObjectId(id, ent);
	}
	CustomEntity1* pEnt;
	acdbOpenObject(pEnt, id, AcDb::kForWrite);
	if (pEnt != nullptr) {
		pEnt->set(AcGePoint3d(3000, 2000, 0), 800, 25, 15);
        // 使用完成之后一定要关闭实体
        pEnt->close();
	}
}

注意事项

  • 必须加载相应的dbx文件，才能对自定义实体进行相应操作，不然只能对自定义实体进行非常有限的操作！
  • 如果dwg图纸中包含自定义实体，但是没有加载相应的dbx文件，这时会以代理图形显示在CAD中，并给出以下提示；当自定义实体文件加载后，会自动还原为自定义实体。

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