ObjectARX學習筆記

一、AutoCAD APIs支持：

1，ObjectARX
2，.NET Managed API
3，COM Automation (VB, Java, Delphi, etc.)
4，AutoLISP

二次開發編程主要採用ObjectARX)和RealDWG，其中ObjectARX是免費的，RealDWG是收費的。

（http://www.autodesk.com/objectarx, 

  http://usa.autodesk.com/adsk/servlet/index?siteID=123112&id=770257）

API架構：

二、ObjectARX

1，ObjectARX是什麼？

     AutoCAD Runtime eXtension

• • A DLL plug-in model
  • A set of Object Oriented C++ libraries
  • A framework

2，ObjectARX能做什麼？

• Modify and extend the drawing database
  • Create/modify/erase objects
    
  • Create new types of objects
    
• Modify AutoCAD’s user interface
  
  • Commands
    
  • Toolbars/dialogs
    
  • Properties Window
    
  • Design Center
    
  • Display system
• Monitor/Modify AutoCAD’s standard behavior
  
  • Event notifications
  • Input point acquisition

3，.ARX = .DLL + 2 exported functions

• acrxEntryPoint
• acrxGetApiVersion

三、ObjectARX架構

AcDbDatabase 結構體系

Block Table:

三個默認的記錄：*MODEL_SPACE, *PAPER_SPACE, *PAPER_SPACE0

實體只有添加到上述三個記錄中才能在AutoCAD中顯示。

AcRxObject  (在 rxobject.h 中定義)

• cast down-cast pointer safely
• isA get class descriptor
• isKindOf is object derived from?

AcDbEntity *ent;
if (ent->isKindOf( AcDbLine::desc()))
{
    AcDbLine *line = AcDbLine::cast(ent);
    //do something with line->startPoint()...
}

四、AutoCAD圖形數據庫

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