[资料] delphi.net二次开发AutoCAD（四）GetPoint 方法
GetPoint 方法提示用户在 AutoCAD 命令提示下给出点的定义。PromptPointOptions 对象允许用户控制输入和如何显示提示信息。PromptPointOptions 对象的 UseBasePoint 和 BasePoint 属性控制是否从基点绘制一条橡皮线。PromptPointOptions 对象的 Keywords 属性允许用户定义用户可以在命令提示中输入除指定点外的关键字。下面的样例提示用户输入两个点，然后以这两个点为起点和端点绘制一条直线（该例子根据用户点击鼠标，获取用户选定的点）namespace ClassLibrary3;
interface
uses
Autodesk.AutoCAD.Runtime, Autodesk.AutoCAD.ApplicationServices,Autodesk.AutoCAD.EditorInput,
Autodesk.AutoCAD.DatabaseServices,Autodesk.AutoCAD.Geometry;
type
Class1 =publicclass
private
public
class method GetPointsFromUser;
end;
implementation
class method Class1.GetPointsFromUser;
var
acDococument;
acCurDbatabase;
pPtResromptPointResult;
pPtOptsromptPointOptions;
ptStartoint3d;
ptEndoint3d;
acTrans:Transaction;
acBlkTbl:BlockTable;
acBlkTblRec:BlockTableRecord;
acLineine;
begin
//获得当前数据库并启动事务管理器 Get the current database and start the Transaction Manager
acDoc:= Application.DocumentManager.MdiActiveDocument;
acCurDb:= acDoc.Database;
pPtOpts:= New PromptPointOptions('');
//提示开始点 Prompt for the start point
pPtOpts.Message := #13+ 'Enter the start point of the line: ';
pPtRes := acDoc.Editor.GetPoint(pPtOpts);
ptStart:= pPtRes.Value;
//如果用户按了 ESC 键或取消了命令就退出 Exit if the user presses ESC or cancels the command
If pPtRes.Status = PromptStatus.Cancel Then Exit;
//提示结束点
pPtOpts.Message :=#13+'Enter the end point of the line:';
pPtOpts.UseBasePoint:=True;
pPtOpts.BasePoint:=ptStart;
pPtRes := acDoc.Editor.GetPoint(pPtOpts);
ptEnd:= pPtRes.Value;
If pPtRes.Status = PromptStatus.Cancel Then Exit;
//启动一个事务
try
acTrans:= acCurDb.TransactionManager.StartTransaction;
//以写的方式打开模型空间
acBlkTbl := acTrans.GetObject(acCurDb.BlockTableId,OpenMode.ForRead) as BlockTable;
acBlkTblRec := acTrans.GetObject(acBlkTbl, OpenMode.ForWrite) as BlockTableRecord;
//定义新的直线
acLine:= New Line(ptStart, ptEnd);
acLine.SetDatabaseDefaults;
//添加直线到图形中去
acBlkTblRec.AppendEntity(acLine);
acTrans.AddNewlyCreatedDBObject(acLine, True);
//缩放到图形的范围或界限
acDoc.SendStringToExecute('._zoom _all ', True, False, False);
finally
//提交修改并销毁事务
acTrans.Commit;
end;
end;
end. 后记：在翻译这一段代码的过程中，出现了一个非委托的错误，原因是我在翻译的时候将下两行代码 acBlkTbl := acTrans.GetObject(acCurDb.BlockTableId,OpenMode.ForRead) as BlockTable;
acBlkTblRec := acTrans.GetObject(acBlkTbl,OpenMode.ForWrite) as BlockTableRecord;
中的as BlockTable和as BlockTableRecord两个运算去掉，加上这两个以后就正常了。
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