ArcGIS Runtime SDK for iOS开发系列教程（7）——GeometryService与GeometryEngine使用

　　在我们使用其他WebAPIs开发应用时，常常会用到GeometryService进行空间位置判断、距离面积量测、缓冲区分析等几何操作。在ArcGIS for Server10.1中提供的GemetryService主要包括以下操作：
　　
那么，在ArcGIS for iOS中通过使用GeometryServiceTask可以很方便地使用ArcGIS的GeometryService，它所包括的操作主要有（下图左侧）：

　　同时，在ArcGIS for iOS中还封装了本地进行几何操作的类——GeometryEngine，极大的提高了几何操作的效率。他所提供的操作主要如上图的右侧。下面我们将通过最简单的缓冲区操作来向大家展示在ArcGIS for iOS中GeometryService和GeometryEngine的使用方法。
　　首先，我们构建一个支持ArcGIS的SDK的工程，在.h文件中添加GeometryServiceTask和相关协议GeometryServiceTaskDelegate，当然包括要素图层的添加，如下图：

　　有了上一讲中Tasks使用流程的实践，相信大家对使用协议的委托模式已经相当熟悉。接下来，我们需要对GeometryServicesTask进行初始化和实现GeometryServiceTaskDelegate的相关方法，首先在AGSMapViewTouchDelegate的地图点击实现方法方法中初始化GeometryServicesTask和相关参数

-(void)mapView:(AGSMapView *)mapView didClickAtPoint:(CGPoint)screen mapPoint:(AGSPoint *)mappoint graphics:(NSDictionary *)graphics

{

NSMutableArray *geometryArray=[NSMutableArray array];

[geometryArray addObject:mappoint];



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

self.gst=[[[AGSGeometryServiceTask alloc]initWithURL:[NSURL URLWithString:kGeometryBufferService]]autorelease];

AGSSpatialReference *sr=[[[AGSSpatialReference alloc]initWithWKID:102100 WKT:nil]autorelease];



self.gst.delegate=self;



AGSBufferParameters *bufferParams=[[AGSBufferParameters alloc]init];

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;



[self.gst bufferWithParameters:bufferParams];

[bufferParams release];



}

　　然后，添加GeometryService执行buffer操作的响应操作，成功返回处理：

-(void)geometryServiceTask:(AGSGeometryServiceTask *)geometryServiceTask operation:(NSOperation *)op didReturnBufferedGeometries:(NSArray *)bufferedGeometries

{

UIAlertView *av = [[UIAlertView alloc] initWithTitle:@"GeometryService"

message:[NSString stringWithFormat:@"成功返回%d个缓冲区！", [bufferedGeometries count]]

delegate:self

cancelButtonTitle:@"确定"

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 (AGSGeometry* g in bufferedGeometries) {



// initialize the graphic for geometry

AGSGraphic *graphic = [[AGSGraphic alloc] initWithGeometry:g symbol:nil attributes:nil infoTemplateDelegate:nil];



// 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];

}

　　可以看出成功执行GeometryService的buffer操作后，返回结果是数组(NSArray *)bufferedGeometries，通过遍历将Geometry转化为要素来展示。另外，我们还需要添加出错的处理：

- (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];

}

　　这个与其他Tasks的提示类似，不做过多解释。这样，我们就完成了使用GeometryServiceTask来实现缓冲区分析的操作。
　　接下来，我们来看如何通过GeometryEngine来实现同样的操作：

-(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

AGSGeometryEngine *geoEng=[AGSGeometryEngine defaultGeometryEngine];



// 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--)

{

AGSPolygon *geBuffer=[geoEng bufferGeometries:geometryArray byDistance:i*1000];

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];

}

　　我们不难发现，使用GeometryEngine实现同样的buffer操作更加便捷，如果你实际操作的话，你还好发现它的效率要比GeomertyServiceTask高很多。
效果：


　　　总结：本讲主要通过GeometryServiceTask和GeometryEngine的使用来向大家展示在ArcGIS for iOS中如何实现几何相关的操作，其他具体操作，如长度计算、面积量测等大家可以参考帮助文档。下一讲将向大家介绍Geoprocessor相关的操作，欢迎大家继续关注！

文章来源：http://www.cnblogs.com/esrichina/archive/2012/11/14/2770779.html