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用AGSImageServiceIdentifyTask能够获取ArcGISImageServiceLayer图层中的栅格值。这涉及了三个比較重要的类：AGSImageServiceIdentifyParameters、AGSImageServiceIdentifyTask和AGSImageServiceIdentifyResult，另一个delegate代理类。以下一一简单介绍一下：
AGSImageServiceIdentifyParameters
AGSImageServiceIdentifyParameters是用来设置identify參数的。能够用类方法imageServiceIdentifyParameters构造，即
[AGSImageServiceIdentifyParameters AGSImageServiceIdentifyParameters];
AGSImageServiceIdentifyParameters共包含以下几个属性
---geometry用于指定查询栅格的位置。经常是一个AGSPoint，也能够用AGSPolygon来查询一个区域的栅格值。
---mosaicRule是镶嵌规则。默觉得AGSMosaicMethodCenter。
---pixelSizeX和pixelSizeY用来设置象元大小，默觉得被查询栅格图层的象元大小。在象元大小范围内的全部镶嵌数据集都会被查询到。
AGSImageServiceIdentifyTask
实例化的时候须要设置查询的URL，假设须要验证的话须要设置credential
其它的没什么可介绍的，在查询的之前已经要为查询设置代理，查询的时候用- (NSOperation*) identifyWithParameters:(AGSImageServiceIdentifyParameters *) identifyParams方法。
AGSImageServiceIdentifyResult
catelogItems是返回的栅格文件夹（我也不知道怎么翻译啦，一个Raster Catelog是Raster Dataset栅格数据集的集合）。
catalogItemVisibilities顾名思义，栅格文件夹是否可见
location就是identify的查询位置
name就是identify查询的属性名称
objectId不解释了。就是一个id
properties是一个属性的集合
value就是name相应属性的象元值
AGSImageServiceIdentifyDelegate
代理是用来获得查询结果用的。必须实现以下两个方法，第一个是identify查询失败的时候调用的，第二个是identify查询成功调用的，会获得一个AGSImageServiceIdentifyResult对象。
(void) - imageServiceIdentifyTask:operation:didFailToIdentifyWithError:
(void) - imageServiceIdentifyTask:operation:didIdentifyWithResult:
以下是详细的用法。
1、为ViewController设置代理，并实现查询完毕的两个方法:
在ViewController.h中
#import <UIKit/UIKit.h>
#define IMAGE_SERVICE "http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/World/MODIS/ImageServer"</p> @interface ViewController : UIViewController <AGSImageServiceIdentifyDelegate> @property (strong, nonatomic) AGSImageServiceIdentifyTask *task; @end
在ViewController.m中
- (void)imageServiceIdentifyTask:(AGSImageServiceIdentifyTask*)identifyTask operation:(NSOperation*)op didIdentifyWithResult:(AGSImageServiceIdentifyResult *)result{
NSLog(@"properties :%@", result.properties);
NSLog(@"value :%@", result.value);
NSLog(@"name : %@", result.name);
NSLog(@"catalogItems count :%d", [[result.catalogItems features] count]);
}
- (void)imageServiceIdentifyTask:(AGSImageServiceIdentifyTask*)identifyTask operation:(NSOperation*)op didFailToIdentifyWithError:(NSError *)error{
NSLog(@"fault");
}2、设置AGSImageServiceIdentifyTask:
self.task = [[AGSImageServiceIdentifyTask alloc] initWithURL:[NSURL URLWithString:IMAGE_SERVICE]];
self.task.delegate = self;
3、设置AGSImageServiceIdentifyParameters:
AGSImageServiceIdentifyParameters *param = [AGSImageServiceIdentifyParameters imageServiceIdentifyParameters];
param.geometry = [AGSPoint pointWithX:116.425541 y:39.969147 spatialReference:[AGSSpatialReference spatialReferenceWithWKID:4326]];
[self.task identifyWithParameters:param];完整的代码例如以下：
ViewController.h中
// ViewController.h
// Wang
//
// Created by dongyu on 14-7-10.
// Copyright (c) 2014年 org.reach. All rights reserved.
// #import <UIKit/UIKit.h> @interface ViewController : UIViewController <AGSImageServiceIdentifyDelegate> @property (strong, nonatomic) AGSImageServiceIdentifyTask *task; @end
在ViewController.m中
// ViewController.m
// Wang
//
// Created by dongyu on 14-7-10.
// Copyright (c) 2014年 org.reach. All rights reserved.
// #import "ViewController.h"
#define IMAGE_SERVICE @"http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/World/MODIS/ImageServer" @interface ViewController () @end @implementation ViewController - (void)viewDidLoad
{
[super viewDidLoad]; self.task = [[AGSImageServiceIdentifyTask alloc] initWithURL:[NSURL URLWithString:IMAGE_SERVICE]];
self.task.delegate = self; AGSImageServiceIdentifyParameters *param = [AGSImageServiceIdentifyParameters imageServiceIdentifyParameters]; param.geometry = [AGSPoint pointWithX:116.425541 y:39.969147 spatialReference:[AGSSpatialReference spatialReferenceWithWKID:4326]]; [self.task identifyWithParameters:param]; } - (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
} #pragma mark - delegate
- (void)imageServiceIdentifyTask:(AGSImageServiceIdentifyTask*)identifyTask operation:(NSOperation*)op didIdentifyWithResult:(AGSImageServiceIdentifyResult *)result{
NSLog(@"properties :%@", result.properties);
NSLog(@"value :%@", result.value);
NSLog(@"name : %@", result.name);
NSLog(@"catalogItems count :%d", [[result.catalogItems features] count]);
} - (void)imageServiceIdentifyTask:(AGSImageServiceIdentifyTask*)identifyTask operation:(NSOperation*)op didFailToIdentifyWithError:(NSError *)error{
NSLog(@"fault");
} @end
demo的下载地址：
http://download.csdn.net/detail/dongyu1009/7623695
新手发博文，有不好的地方，望大家批评指正。