ArcGIS Runtime SDK for iOS开发系列课程（7）——GeometryService与GeometryEngine使用
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];
}
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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！