engine的工具中实现Snapping(捕捉)

http://blog.csdn.net/rrrrssss00/article/details/5809184 在Engine的工具(ITool)里:   OnClick事件处理函数中: 首先需要获取一个图层,作为Snapping的参照, IFeatureLayer targetLayer   然后声明一个IMovePointFeedBack作为鼠标移动时捕捉点的显示: [c-sharp]view plaincopyprint?
  1. IMovePointFeedback m_pMovePtFeed = new MovePointFeedback();
  2. mFeedback = (IDisplayFeedback)m_pMovePtFeed;
  3. ISimpleMarkerSymbol simpleMarkerSymbol = new SimpleMarkerSymbolClass();
  4. IRgbColor pRGBColor = new RgbColorClass();
  5. pRGBColor.Red = 0;
  6. pRGBColor.Green = 0;
  7. pRGBColor.Blue = 0;
  8. simpleMarkerSymbol.Color = pRGBColor;
  9. simpleMarkerSymbol.Size = 3;
  10. simpleMarkerSymbol.Style = ESRI.ArcGIS.Display.esriSimpleMarkerStyle.esriSMSSquare;
  11. ISymbol symbol = simpleMarkerSymbol as ISymbol;
  12. symbol.ROP2 = esriRasterOpCode.esriROPNotXOrPen;
  13. //symbol.ROP2 = esriRasterOpCode.;
  14. m_pMovePtFeed.Symbol = (ISymbol)simpleMarkerSymbol;
IMovePointFeedback m_pMovePtFeed = new MovePointFeedback(); mFeedback = (IDisplayFeedback)m_pMovePtFeed; ISimpleMarkerSymbol simpleMarkerSymbol = new SimpleMarkerSymbolClass(); IRgbColor pRGBColor = new RgbColorClass(); pRGBColor.Red = 0; pRGBColor.Green = 0; pRGBColor.Blue = 0; simpleMarkerSymbol.Color = pRGBColor; simpleMarkerSymbol.Size = 3; simpleMarkerSymbol.Style = ESRI.ArcGIS.Display.esriSimpleMarkerStyle.esriSMSSquare; ISymbol symbol = simpleMarkerSymbol as ISymbol; symbol.ROP2 = esriRasterOpCode.esriROPNotXOrPen; //symbol.ROP2 = esriRasterOpCode.; m_pMovePtFeed.Symbol = (ISymbol)simpleMarkerSymbol;   然后开始Feedback的显示(tmpPoint是指开始的点,其实影响不大,如果不想要源点在屏幕上的话,可以取一个在屏幕外的点): [c-sharp]view plaincopyprint?
  1. m_pMovePtFeed.Display = mMapControl.ActiveView.ScreenDisplay;
  2. m_pMovePtFeed.Start(tmpPoint, tmpPoint);
m_pMovePtFeed.Display = mMapControl.ActiveView.ScreenDisplay;m_pMovePtFeed.Start(tmpPoint, tmpPoint);   在OnMouseMove事件中: [c-sharp]view plaincopyprint?
  1. IPoint pPoint2 = null;
  2. IPoint pPoint = pMap.ActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(x, y);
  3. pPoint2 = Snapping(pPoint.X, pPoint.Y, targetLayer, pMap, 10);
  4. if (pPoint2 == null)
  5. pPoint2 = pPoint;
  6. ((IMovePointFeedback)mFeedback).MoveTo(pPoint2);
IPoint pPoint2 = null; IPoint pPoint = pMap.ActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(x, y); pPoint2 = Snapping(pPoint.X, pPoint.Y, targetLayer, pMap, 10); if (pPoint2 == null) pPoint2 = pPoint; ((IMovePointFeedback)mFeedback).MoveTo(pPoint2);   其中Snapping函数即为最主要的查找函数,其功能为根据输入的点坐标在目标图层上查找最为相近的点(也即需要捕捉的点),返回该点,若没有找到则返回NULL,最后一个参数的含义是,在地图控件上,以多少个像素为单位在周边查找捕捉点. [c-sharp]view plaincopyprint?
  1. public IPoint Snapping(double x, double y, IFeatureLayer iFeatureLyr, IMapControl3 axMapControl1,double snappingDis)
  2.         {
  3.             IPoint iHitPoint = null;
  4.             IMap iMap = axMapControl1.Map;
  5.             IActiveView iView = axMapControl1.ActiveView;
  6.             IFeatureClass iFClss = iFeatureLyr.FeatureClass;
  7.             IPoint point = new PointClass();
  8.             point.PutCoords(x, y);
  9.             double length = ConvertPixelsToMapUnits(axMapControl1.ActiveView, snappingDis);
  10.             ITopologicalOperator pTopo = point as ITopologicalOperator;
  11.             IGeometry pGeometry = pTopo.Buffer(length).Envelope as IGeometry;
  12.             ISpatialFilter spatialFilter = new SpatialFilterClass();
  13.             spatialFilter.GeometryField = iFeatureLyr.FeatureClass.ShapeFieldName;
  14.             spatialFilter.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects;
  15.             spatialFilter.Geometry = pGeometry;
  16.             IFeatureCursor cursor = iFClss.Search(spatialFilter, false);
  17.             IFeature iF = cursor.NextFeature();
  18.             if (iF == null) return null;
  19.             IPoint iHitPt = new ESRI.ArcGIS.Geometry.Point();
  20.             IHitTest iHitTest = iF.Shape as IHitTest;
  21.             double hitDist = 0;
  22.             int partIndex = 0;
  23.             int vertexIndex = 0;
  24.             bool bVertexHit = false;
  25.             // Tolerance in pixels for line hits
  26.             double tol = ConvertPixelsToMapUnits(iView, snappingDis);
  27.             if (iHitTest.HitTest(point, tol, esriGeometryHitPartType.esriGeometryPartBoundary,
  28.                 iHitPt, ref hitDist, ref partIndex, ref vertexIndex, ref bVertexHit))
  29.             {
  30.                 iHitPoint = iHitPt;
  31.             }
  32.             //axMapControl1.ActiveView.Refresh();
  33.             return iHitPoint;
  34.         }
  35.         public double ConvertPixelsToMapUnits(IActiveView pActiveView, double pixelUnits)
  36.         {
  37.             double realWorldDisplayExtent;
  38.             int pixelExtent;
  39.             double sizeOfOnePixel;
  40.             pixelExtent = pActiveView.ScreenDisplay.DisplayTransformation.get_DeviceFrame().right - pActiveView.ScreenDisplay.DisplayTransformation.get_DeviceFrame().left;
  41.             realWorldDisplayExtent = pActiveView.ScreenDisplay.DisplayTransformation.VisibleBounds.Width;
  42.             sizeOfOnePixel = realWorldDisplayExtent / pixelExtent;
  43.             return pixelUnits * sizeOfOnePixel;
  44.         }
publicIPoint Snapping(double x, double y, IFeatureLayer iFeatureLyr,IMapControl3 axMapControl1,double snappingDis) { IPoint iHitPoint =null; IMap iMap = axMapControl1.Map; IActiveView iView =axMapControl1.ActiveView; IFeatureClass iFClss =iFeatureLyr.FeatureClass; IPoint point = new PointClass();point.PutCoords(x, y); double length =ConvertPixelsToMapUnits(axMapControl1.ActiveView, snappingDis);ITopologicalOperator pTopo = point as ITopologicalOperator; IGeometrypGeometry = pTopo.Buffer(length).Envelope as IGeometry; ISpatialFilterspatialFilter = new SpatialFilterClass(); spatialFilter.GeometryField =iFeatureLyr.FeatureClass.ShapeFieldName; spatialFilter.SpatialRel =esriSpatialRelEnum.esriSpatialRelIntersects; spatialFilter.Geometry =pGeometry; IFeatureCursor cursor = iFClss.Search(spatialFilter, false);IFeature iF = cursor.NextFeature(); if (iF == null) return null; IPointiHitPt = new ESRI.ArcGIS.Geometry.Point(); IHitTest iHitTest = iF.Shapeas IHitTest; double hitDist = 0; int partIndex = 0; int vertexIndex =0; bool bVertexHit = false; // Tolerance in pixels for line hits doubletol = ConvertPixelsToMapUnits(iView, snappingDis); if(iHitTest.HitTest(point, tol,esriGeometryHitPartType.esriGeometryPartBoundary, iHitPt, ref hitDist,ref partIndex, ref vertexIndex, ref bVertexHit)) { iHitPoint = iHitPt;} //axMapControl1.ActiveView.Refresh(); return iHitPoint; } publicdouble ConvertPixelsToMapUnits(IActiveView pActiveView, doublepixelUnits) { double realWorldDisplayExtent; int pixelExtent; doublesizeOfOnePixel; pixelExtent =pActiveView.ScreenDisplay.DisplayTransformation.get_DeviceFrame().right-pActiveView.ScreenDisplay.DisplayTransformation.get_DeviceFrame().left;realWorldDisplayExtent =pActiveView.ScreenDisplay.DisplayTransformation.VisibleBounds.Width;sizeOfOnePixel = realWorldDisplayExtent / pixelExtent; returnpixelUnits * sizeOfOnePixel; }   此时即可实现鼠标实时地捕捉目标图层上的对象,若需要获取当前位置的捕捉点时,则可以在相应事件(例如OnMouseDown或OnDbClick)中调用: [c-sharp]view plaincopyprint?
  1. IPoint pPoint = ((IMovePointFeedback)mFeedback).Stop();
IPoint pPoint = ((IMovePointFeedback)mFeedback).Stop(); 这时实时捕捉将会停止,若需要重新开始捕捉,则在之后调用这些语句即可: [c-sharp]view plaincopyprint?
  1. //重新开始Snap
  2. IPoint tmpPoint = new PointClass();
  3. tmpPoint.PutCoords(pMap.Extent.XMin - 1, pMap.Extent.YMin - 1);
  4. IMovePointFeedback m_pMovePtFeed = (IMovePointFeedback)mFeedback;
  5. m_pMovePtFeed.Display = pMap.ActiveView.ScreenDisplay;
  6. m_pMovePtFeed.Start(tmpPoint, tmpPoint);
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原文地址：https://www.cnblogs.com/adodo1/p/4328014.html