首發地址：http://www.cnblogs.com/esrichina/archive/2012/11/14/2770779.html
在我們使用其他WebAPIs開發應用時，常常會用到GeometryService進行空間位置判斷、距離面積量測、緩衝區分析等幾何操作。在ArcGIS for Server10.1中提供的GemetryService主要包括以下操作：
那麼，在ArcGIS
for iOS中通過使用GeometryServiceTask可以很方便地使用ArcGIS的GeometryService，它所包括的操作主要有（下圖左側）：
同時，在ArcGIS for iOS中還封裝了本地進行幾何操作的類——GeometryEngine，極大的提高了幾何操作的效率。他所提供的操作主要如上圖的右側。下面我們將通過最簡單的緩衝區操作來向大家展示在ArcGIS for iOS中GeometryService和GeometryEngine的使用方法。
首先，我們構建一個支持ArcGIS的SDK的工程，在.h文件中添加GeometryServiceTask和相關協議GeometryServiceTaskDelegate，當然包括要素圖層的添加，如下圖：
有了上一講中Tasks使用流程的實踐，相信大家對使用協議的委託模式已經相當熟悉。接下來，我們需要對GeometryServicesTask進行初始化和實現GeometryServiceTaskDelegate的相關方法，首先在AGSMapViewTouchDelegate的地圖點擊實現方法方法中初始化GeometryServicesTask和相關參數
-(void)mapView:(AGSMapView
*)mapView didClickAtPoint:(CGPoint)screen mapPoint:(AGSPoint *)mappoint graphics:(NSDictionary *)graphics{ NSMutableArray *geometryArray=[NSMutableArray array]; <span
style="background-color:
#ffcc00;">[geometryArray
addObject:mappoint];</span> AGSPictureMarkerSymbol
*pt=[AGSPictureMarkerSymbol pictureMarkerSymbolWithImageNamed:@"ArcGIS.bundle/GPSDisplay.png"]; AGSGraphic
*pushpin=[[AGSGraphic alloc]initWithGeometry:mappoint symbol:pt attributes:nil infoTemplateDelegate:nil]; [_graphicsLayer
addGraphic:pushpin]; [pushpin
release]; [_graphicsLayer
dataChanged]; [_mapView
centerAtPoint:mappoint animated:YES]; //GeometryService <span
style="background-color:
#ffcc00;">self.gst=[[[AGSGeometryServiceTask
alloc]initWithURL:[NSURL URLWithString:kGeometryBufferService]]autorelease];</span> AGSSpatialReference
*sr=[[[AGSSpatialReference alloc]initWithWKID:102100 WKT:nil]autorelease]; <span
style="background-color:
#ffcc00;">self.gst.delegate=self;</span> <span
style="background-color:
#ffcc00;">AGSBufferParameters
*bufferParams=[[AGSBufferParameters alloc]init];</span> bufferParams.unit=kesriSRUnit_Meter; bufferParams.bufferSpatialReference=sr; bufferParams.distances
= [NSArray arrayWithObjects: [NSNumber numberWithUnsignedInteger:10000], [NSNumber numberWithUnsignedInteger:30000], [NSNumber numberWithUnsignedInteger:50000], nil]; bufferParams.geometries
= geometryArray; bufferParams.outSpatialReference
= sr; bufferParams.unionResults
= FALSE; <span
style="background-color:
#ffcc00;">[self.gst
bufferWithParameters:bufferParams];</span> [bufferParams
release]; } |
然後，添加GeometryService執行buffer操作的響應操作，成功返回處理：
-(void)geometryServiceTask:(AGSGeometryServiceTask
*)geometryServiceTask operation:(NSOperation *)op
didReturnBufferedGeometries:<span style="background-color:
#ffcc00;">(NSArray *)bufferedGeometries</span>{ UIAlertView
*av = [[UIAlertView alloc] initWithTitle:@"GeometryService" message:[NSString stringWithFormat:@"成功返回%d個緩衝區！",
[bufferedGeometries count]] delegate:self cancelButtonTitle:@"確定" otherButtonTitles:nil]; [av
show]; [av
release]; //
Create a SFS for the inner buffer zone AGSSimpleFillSymbol
*innerSymbol = [AGSSimpleFillSymbol simpleFillSymbol]; innerSymbol.color
= [[UIColor redColor] colorWithAlphaComponent:0.40]; innerSymbol.outline.color
= [UIColor darkGrayColor]; //
Create a SFS for the outer buffer zone AGSSimpleFillSymbol
*outerSymbol = [AGSSimpleFillSymbol simpleFillSymbol]; outerSymbol.color
= [[UIColor yellowColor] colorWithAlphaComponent:0.25]; outerSymbol.outline.color
= [UIColor darkGrayColor]; //
counter to help us determine if the geometry returned is inner/outer NSUInteger i
= 0; for (<span
style="background-color:
#ffcc00;">AGSGeometry*
g in bufferedGeometries</span>) { //
initialize the graphic for geometry <span
style="background-color:
#ffcc00;">AGSGraphic
*graphic = [[AGSGraphic alloc] initWithGeometry:g symbol:nil attributes:nil infoTemplateDelegate:nil];</span> //
since we have 2 buffer distances, we know that 0-2 will be 100m buffer and 3-5 will be 300m buffer if (i
< [bufferedGeometries count]/2) { graphic.symbol
= innerSymbol; } else { graphic.symbol
= outerSymbol; } //
add graphic to the graphic layer [self.graphicsLayer
addGraphic:graphic]; //
release our alloc'd graphic [graphic
release]; //
increment counter so we know which index we are at i++; } //
let the graphics layer know it has new graphics to draw [self.graphicsLayer
dataChanged]; } |
可以看出成功執行GeometryService的buffer操作後，返回結果是數組(NSArray *)bufferedGeometries，通過遍歷將Geometry轉化爲要素來展示。另外，我們還需要添加出錯的處理：
-
(void)geometryServiceTask:(AGSGeometryServiceTask
*)geometryServiceTask operation:(NSOperation*)op
didFailBufferWithError:(NSError *)error
{ UIAlertView
*av = [[UIAlertView alloc] initWithTitle:@"Error" message:@"There
was an error with the buffer task" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil]; [av
show]; [av
release];} |
這個與其他Tasks的提示類似，不做過多解釋。這樣，我們就完成了使用GeometryServiceTask來實現緩衝區分析的操作。
接下來，我們來看如何通過GeometryEngine來實現同樣的操作：
-(void)mapView:(AGSMapView
*)mapView didClickAtPoint:(CGPoint)screen mapPoint:(AGSPoint *)mappoint graphics:(NSDictionary *)graphics{ NSMutableArray *geometryArray=[NSMutableArray array]; [geometryArray
addObject:mappoint]; //[_graphicsLayer
removeAllGraphics]; AGSPictureMarkerSymbol
*pt=[AGSPictureMarkerSymbol pictureMarkerSymbolWithImageNamed:@"ArcGIS.bundle/GPSDisplay.png"]; AGSGraphic
*pushpin=[[AGSGraphic alloc]initWithGeometry:mappoint symbol:pt attributes:nil infoTemplateDelegate:nil]; [_graphicsLayer
addGraphic:pushpin]; [pushpin
release]; [_graphicsLayer
dataChanged]; [_mapView
centerAtPoint:mappoint animated:YES]; //GeometryEngine <span
style="background-color:
#ffcc00;">AGSGeometryEngine
*geoEng=[AGSGeometryEngine defaultGeometryEngine];</span> //
Create a SFS for the inner buffer zone AGSSimpleFillSymbol
*innerSymbol = [AGSSimpleFillSymbol simpleFillSymbol]; innerSymbol.color
= [[UIColor redColor] colorWithAlphaComponent:0.40]; innerSymbol.outline.color
= [UIColor darkGrayColor]; //
Create a SFS for the outer buffer zone AGSSimpleFillSymbol
*outerSymbol = [AGSSimpleFillSymbol simpleFillSymbol]; outerSymbol.color
= [[UIColor yellowColor] colorWithAlphaComponent:0.25]; outerSymbol.outline.color
= [UIColor darkGrayColor]; for (int i=10;
i>0;i--) { <span
style="background-color:
#ffcc00;">AGSPolygon
*geBuffer=[geoEng bufferGeometries:geometryArray byDistance:i*1000];</span> AGSGraphic
*gr = [[AGSGraphic alloc] initWithGeometry:geBuffer symbol:nil attributes:nil infoTemplateDelegate:nil]; if (i%2==1) { gr.symbol=outerSymbol; } else { gr.symbol=innerSymbol; }
//[self.graphicsLayer
addGraphic:gr]; } [self.graphicsLayer
dataChanged];} |
我們不難發現，使用GeometryEngine實現同樣的buffer操作更加便捷，如果你實際操作的話，你還好發現它的效率要比GeomertyServiceTask高很多。
效果：
總結：本講主要通過GeometryServiceTask和GeometryEngine的使用來向大家展示在ArcGIS for iOS中如何實現幾何相關的操作，其他具體操作，如長度計算、面積量測等大家可以參考幫助文檔。下一講將向大家介紹Geoprocessor相關的操作，歡迎大家繼續關注！