ArcEngine——异步执行GP工具(Background geoprocessing)

从ArcGIS 10开始，ArcGIS开始支持后台地理处理。使用Geoprocessor.ExecuteAsync()方法，可以在ArcGIS应用程序的后台执行工具或模型工具。也就是说当工具在后台进程中执行时，ArcGIS控件(例如，MapControl、PageLayoutControl、GlobeControl或SceneControl)保持对用户交互的响应。换句话说，可以在工具执行时查看和查询数据。
使用后台地理处理来执行一个工具，需要以下操作：

　　1、注册事件
　　2、提交工具执行。

 1：Geoprocessor方式

　　Geoprocessor类提供了以下5种事件：

• MessagesCreated
• ProgressChanged
• ToolboxChanged
• ToolExecuted
• ToolExecuting

　　本文主要介绍ToolExecuting和ToolExecuted事件。

　　1. 实例化Geoprocessor类

Geoprocessor gp = new GeoProcessor();
gp.OverwriteOutput = true;　　

　　2.注册事件

　　这里根据需求，用到哪些事件就注册哪些事件。

gp.ToolExecuting += new EventHandler<ToolExecutingEventArgs>(gp_ToolExecuting);
gp.ToolExecuted += new EventHandler<ToolExecutedEventArgs>(gp_ToolExecuted);

　　3.创建一个队列用于存放gp工具

private Queue<IGPProcess> _myGPToolsToExecute = new Queue<IGPProcess>();

　　4.事件处理函数

//此处只是为了演示，具体内容可以实际需求编写，例如执行完毕后将结果加载到MapControl中
private void gp_ToolExecuted(object sender, ToolExecutedEventArgs e)
{
    IGeoProcessorResult2 gpResult = (IGeoProcessorResult2)e.GPResult;

    if (gpResult.Status == esriJobStatus.esriJobSucceeded)
    {
        Console.WriteLine(gpResult.Process.ToolName.ToString() + "执行完毕");
        //判断队列里是否还有工具，如果有继续执行
        if (_myGPToolsToExecute.Count > 0)
        {
            gp.ExecuteAsync(_myGPToolsToExecute.Dequeue());
        }
    }
    else if (gpResult.Status == esriJobStatus.esriJobFailed)
    {
        Console.WriteLine(gpResult.Process.Tool.Name + "执行失败");
    }
}

private void gp_ToolExecuting(object sender, ToolExecutingEventArgs e)
{
    IGeoProcessorResult2 gpResult = (IGeoProcessorResult2)e.GPResult;
    Console.WriteLine(gpResult.Process.Tool.Name + " " + gpResult.Status.ToString());
}    

　　5.提交工具执行

　　此处以缓冲区分析和裁剪为例。先创建缓冲区，然后用创建的缓冲区裁剪

try
{
                
//缓冲区
ESRI.ArcGIS.AnalysisTools.Buffer bufferTool = new ESRI.ArcGIS.AnalysisTools.Buffer();
bufferTool.in_features = @"C:UsersDemaciaDesktop展示控制点.shp";
bufferTool.buffer_distance_or_field = 1500;
bufferTool.out_feature_class = @"C:UsersDemaciaDesktop展示缓冲区.shp";
                
//裁剪
ESRI.ArcGIS.AnalysisTools.Clip clipTool = new ESRI.ArcGIS.AnalysisTools.Clip();
clipTool.in_features = @"C:UsersDemaciaDesktop展示China_Project.shp";
clipTool.clip_features = bufferTool.out_feature_class;
clipTool.out_feature_class = @"C:UsersDemaciaDesktop展示Clip.shp";
 
//将两个gp工具依次加入队列               
_myGPToolsToExecute.Enqueue(bufferTool);
_myGPToolsToExecute.Enqueue(clipTool);

gp.ExecuteAsync(_myGPToolsToExecute.Dequeue());
                
}
catch (Exception ex)
{
                
}

2：GeoProcessorClass方式

　　此种方式需要使用IGeoProcessor2接口的RegisterGeoProcessorEvents3()方法注册事件。RegisterGeoProcessorEvents3()方法的参数为一个IGeoProcessorEvents3类型的实例，AO中并没有提供实现IGeoProcessorEvents3接口的类，所以需要我们自己创建一个类并实现IGeoProcessorEvents3接口。

　　1.创建一个名为GeoProcessorEvents3Class的类，并实现IGeoProcessorEvents3接口

public class GeoProcessorEvents3Class : IGeoProcessorEvents3
{
    IMapControl2 mapCon;
    public GeoProcessorEvents3Class(IMapControl2 inCon)
    {
        mapCon = inCon;
    }

    public void OnProcessMessages(IGeoProcessorResult result, ESRI.ArcGIS.Geodatabase.IGPMessages pMsgs)
    {
　　　　　//可输出处理过程中产生的信息　　
    }

    public void OnProgressMessage(IGeoProcessorResult result, string message)
    {
　　　　　//可输出处理过程中产生的信息
    }

    public void OnProgressPercentage(IGeoProcessorResult result, double percentage)
    {

    }

    public void OnProgressShow(IGeoProcessorResult result, bool Show)
    {

    }

    /// <summary>
    /// 运行结束后触发此事件
    /// </summary>
    /// <param name="result"></param>
    public void PostToolExecute(IGeoProcessorResult result)
    {
        //此处需要根据实际情况编写 可以改进成委托或事件形式
        //此示例以缓冲区分析为例，执行成功后将缓冲区分析结果添加到MapControl中
        if (result.Status == esriJobStatus.esriJobSucceeded)
        {
            IGPUtilities4 gpu = new GPUtilitiesClass() as IGPUtilities4;
            IFeatureLayer player = new FeatureLayerClass();
            player.FeatureClass = gpu.Open(result.GetOutput(0)) as IFeatureClass;
            mapCon.AddLayer(player as ILayer);

        }
        else if(result.Status == esriJobStatus.esriJobFailed)
        {
            Console.WriteLine("运行失败");
        }
    }

    /// <summary>
    /// 运行前触发此事件
    /// </summary>
    /// <param name="result"></param>
    public void PreToolExecute(IGeoProcessorResult result)
    {
        Console.WriteLine("等待运行GP工具");
    }
} 

　　2.实例化GeoProcessorEvents3Class类、GeoProcessorClass类并注册事件

IGeoProcessorEvents3 GeoProcessorEvents = new GeoProcessorEvents3Class(this.axMapControl1.Object as IMapControl2);
IGeoProcessor2 gp = new GeoProcessorClass();
gp.OverwriteOutput = true;
gp.RegisterGeoProcessorEvents3(GeoProcessorEvents);

　　3.提交工具执行

IVariantArray varParam = new VarArrayClass();
varParam.Add(@"C:UsersDemaciaDesktop展示控制点.shp");
varParam.Add(@"C:UsersDemaciaDesktop展示缓冲区.shp");
varParam.Add(2000);

gp.ExecuteASync("Buffer_analysis", varParam);