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

      首发地址：http://www.cnblogs.com/esrichina/archive/2012/11/14/2770779.html

      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];

    <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:<span style="background-color: #ffcc00;">(NSArray *)bufferedGeometries</span>

{

    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 (<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

    <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！