DotSpatial性能测试（关于DotSpatial要素图层闪烁的问题）

精良的架构设计，健壮的代码使DotSpatial十分强大。近日某人说DotSpatial有闪烁问题，我半信半疑，决定亲自试验一下。首先新建一个地图函数，取名为MultithreadFunction，声明一些变量，代码如下：

using DotSpatial.Controls;
using DotSpatial.Data;
using DotSpatial.Symbology;
using DotSpatial.Topology;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace CustomLayer
{
    class MultithreadFunction : MapFunction
    {
        MapGroup layerGroup;
        List<Thread> threads;
        bool bRunning;
        private const double COORDINATE_STARTX = 880468.25;
        private const double COORDINATE_STARTY = 3828144.59;
        private Random random;
        private Extent orignalExtent;

        public MultithreadFunction(IMap mapCtrl, MapGroup layerGroup)
            : base(mapCtrl)
        {
            this.layerGroup = layerGroup;
            threads = new List<Thread>();
            random = new Random();
            bRunning = false;
        }
    }
}

layerGroup是一个图层组，增加到地图控件即可。图层组可以容纳多个图层。threads是线程列表。为了进行压力测试，我将开启十个线程，100个图层，同时刷新。bRunning变量是线程是否运行的标志。两个常量坐标是北京54坐标系（中央经线105度，高斯三度带投影，东向加常数是50公里，单位是米）下武汉市东西湖区某个位置的坐标。random用来产生随机坐标。originalExtent用来记录此地图函数激活前的视野范围，以便此地图函数失效后还原地图控件的视野。

一、重载地图函数激活事件，初始化图层、线程列表等 等，代码如下：

protected override void OnActivate()
        {
            base.OnActivate();
            layerGroup.Layers.Clear();
            orignalExtent = Map.ViewExtents;
            Map.ViewExtents = new Extent(COORDINATE_STARTX + 5000, COORDINATE_STARTY, COORDINATE_STARTX + 105000, COORDINATE_STARTY + 100000);
            for (var i = 1; i <= 200; i++)
            {
                var layer = new MapLineLayer();
                var coord = new Coordinate(COORDINATE_STARTX, COORDINATE_STARTY + i * 5000);
                layer.Symbolizer = new LineSymbolizer(Color.Red, 2.5);
                layer.FeatureSet.AddFeature(new Feature(FeatureType.Line, new List<Coordinate>() { coord, coord }));
                layerGroup.Layers.Add(layer);
            }
            for (var i = 0; i < 10; i++)
                threads.Add(new Thread(DoThread) { });
            bRunning = true;
            foreach (var t in threads)
                t.Start();
        }

二、声明线程体，执行添加随机坐标点，以简单锁的形式保证多线程加坐标的安全性，代码如下：

private void DoThread(object obj)
        {
            while (bRunning)
            {
                lock (layerGroup)
                {
                    for (var i = 0; i < layerGroup.Layers.Count; i++)
                    {
                        var line = layerGroup.Layers[i] as MapLineLayer;
                        var coords = line.FeatureSet.Features[0].Coordinates;
                        var coord = new Coordinate(coords.Last().X + random.Next(1000, 5000), COORDINATE_STARTY + i * 5000 + random.Next(1000, 5000));
                        coords.Add(coord);
                        line.FeatureSet.InitializeVertices();
                    }
                }
                Map.ViewExtents = Map.ViewExtents;
                Thread.Sleep(random.Next(2000, 5000));
            }
        }

三、重载地图函数失效事件，结束并清理线程，代码如下：

protected override void OnDeactivate()
        {
            base.OnDeactivate();
            bRunning = true;
            foreach (var thread in threads)
                thread.Abort();
            threads.Clear();
            Map.ViewExtents = orignalExtent;
        }

实验证明，在保证1000的并发量下，地图偶尔会闪烁一下。其它情况下，地图运行非常流程。这一点DotSpatial不比ArcGIS逊色，一次为DotSpatial点赞。下面是运行效果截图：

转载于:https://my.oschina.net/zhtqs/blog/1509839