WorldWind学习系列五：插件加载过程全解析

　　不得不承认World Wind的代码真的很庞大，没有太多帮助文档的前提下，一头钻进代码里肯定令你头疼的，甚至研究代码间关联仿佛是在走迷宫。我最近一直想弄明白如何在MenuBar中加载那些插件的，WorldWind学习系列四中研究的只是特殊的三个功能加载的，那三个没有继承Plugin类，不算是插件功能加载。所以WorldWind学习系列四加载的三个是特殊情况，不是一般的插件加载。今天下午终于柳暗花明，如果你真正关注World Wind分析，那么就好好看看下面的插件加载过程全解析。

      我们先看看Plugin类的继承图，看看到底都有些什么插件，然后在分析一般性的插件加载全过程。

　　哦，原来这么多插件，我们要基于WW开发自己的应用，只需继承Plugin类写出自己的插件功能即可的。

     我们现在分析插件加载过程，请确保你看过WorldWind学习系列二：擒贼先擒王篇2 中的（5.加载上次使用的配置信息）。加载的插件入口就是WorldWind.cs的Main()中调用的LoadSettings()静态方法。

　　1.读取WorldWind的配置中插件信息

private static void LoadSettings()
        {
            try
            {
　　　　//先读取上次使用时保存的“使用插件配置文件”，如果存在，则从文件中读取配置实例化WorldWindSettings
                Settings = (WorldWindSettings) SettingsBase.Load(Settings, SettingsBase.LocationType.User);

                if(!File.Exists(Settings.FileName))
                {
　　　　　　　　　　　//我们假定是配置文件不存在，这就是一个个地加载插件，保存到ArrayList中　
                    Settings.PluginsLoadedOnStartup.Add("ShapeFileInfoTool");
                    //Settings.PluginsLoadedOnStartup.Add("OverviewFormLoader");
                    //Settings.PluginsLoadedOnStartup.Add("Atmosphere");
                    Settings.PluginsLoadedOnStartup.Add("SkyGradient");
                    Settings.PluginsLoadedOnStartup.Add("BmngLoader");
                    //Settings.PluginsLoadedOnStartup.Add("Compass");
                    //Settings.PluginsLoadedOnStartup.Add("ExternalLayerManagerLoader");
                    Settings.PluginsLoadedOnStartup.Add("MeasureTool");
                    //Settings.PluginsLoadedOnStartup.Add("MovieRecorder");
                    Settings.PluginsLoadedOnStartup.Add("NRLWeatherLoader");
                    Settings.PluginsLoadedOnStartup.Add("ShapeFileLoader");
                    Settings.PluginsLoadedOnStartup.Add("Stars3D");
                    Settings.PluginsLoadedOnStartup.Add("GlobalClouds");
                    Settings.PluginsLoadedOnStartup.Add("PlaceFinderLoader");
                    Settings.PluginsLoadedOnStartup.Add("LightController");

                    Settings.PluginsLoadedOnStartup.Add("Earthquake_2.0.2.1");
                    Settings.PluginsLoadedOnStartup.Add("Historical_Earthquake_2.0.2.2");
                    Settings.PluginsLoadedOnStartup.Add("KMLImporter");
                    //Settings.PluginsLoadedOnStartup.Add("doublezoom");
                    //Settings.PluginsLoadedOnStartup.Add("PlanetaryRings");
                    Settings.PluginsLoadedOnStartup.Add("TimeController");
                    //Settings.PluginsLoadedOnStartup.Add("WavingFlags");
                    Settings.PluginsLoadedOnStartup.Add("ScaleBarLegend");
                    Settings.PluginsLoadedOnStartup.Add("Compass3D");
                    Settings.PluginsLoadedOnStartup.Add("AnaglyphStereo");
                    Settings.PluginsLoadedOnStartup.Add("GlobeIcon");

                }
                // decrypt encoded user credentials
                DataProtector dp = new DataProtector(DataProtector.Store.USE_USER_STORE);

                if(Settings.ProxyUsername.Length > 0) Settings.ProxyUsername = dp.TransparentDecrypt(Settings.ProxyUsername);
                if(Settings.ProxyPassword.Length > 0) Settings.ProxyPassword = dp.TransparentDecrypt(Settings.ProxyPassword);
            }
            catch(Exception caught)
            {
                Log.Write(caught);
            }
        }

　　2.Main()中后面调用MainApplication()方法，该MainApplication()调用OpenStartupWorld()，用来初始化启动World对象。OpenStartupWorld()方法首先确定加载的是Earth/Moon等，然后开始加载一个星球。

        /// <summary>
        /// Loads a new planet
        /// </summary>
        private void OpenWorld(string worldXmlFile)
        {
            
            if(this.worldWindow.CurrentWorld != null)
            {
                try
                {
                    this.worldWindow.ResetToolbar();
                }
                catch
                {}

                try
                {
                    foreach(PluginInfo p in this.compiler.Plugins)
                    {
                        try
                        {
                            if(p.Plugin.IsLoaded)
                                p.Plugin.Unload();
                        }
                        catch
                        {}
                    }
                }
                catch
                {}
                
                try
                {
                    this.worldWindow.CurrentWorld.Dispose();
                }
                catch
                {}
                
            }


            if(this.gotoDialog != null)
            {
                this.gotoDialog.Dispose();
                this.gotoDialog = null;
            }

            if(this.rapidFireModisManager != null)
            {
                this.rapidFireModisManager.Dispose();
                this.rapidFireModisManager = null;
            }

            if(this.animatedEarthMananger != null)
            {
                this.animatedEarthMananger.Dispose();
                this.animatedEarthMananger = null;
            }

            if(this.wmsBrowser != null)
            {
                this.wmsBrowser.Dispose();
                this.wmsBrowser = null;
            }
            worldWindow.CurrentWorld = WorldWind.ConfigurationLoader.Load(worldXmlFile, worldWindow.Cache);
            this.splashScreen.SetText("Initializing menus...");
            // InitializePluginCompiler()是我们要关注的初始化插件编辑器PluginCompiler（真正管理加载插件的类）
            InitializePluginCompiler();
　　　　　　　
　　　　　　　//RenderableObject系统很复杂，我们稍后准备专门分析一下
            foreach(RenderableObject worldRootObject in this.worldWindow.CurrentWorld.RenderableObjects.ChildObjects)
            {
                this.AddLayerMenuButtons(this.worldWindow, worldRootObject);
            }
            //加载Earth专有的MenuButton( AnimatedEarthManager和RapidFireModisManager)的配置，
            //这里主要不关注
            this.AddInternalPluginMenuButtons();

            this.menuItemModisHotSpots.Enabled = worldWindow.CurrentWorld.IsEarth;
            this.menuItemAnimatedEarth.Enabled = worldWindow.CurrentWorld.IsEarth;
        }

　　3.我们看看InitializePluginCompiler()如何加载插件的？

        /// <summary>
        /// Compile and run plug-in "scripts"
        /// </summary>
        private void InitializePluginCompiler()
        {
            Log.Write(Log.Levels.Debug, "CONF", "initializing plugin compiler...");
            this.splashScreen.SetText("Initializing plugins...");
            string pluginRoot = Path.Combine(DirectoryPath, "Plugins");
            compiler = new PluginCompiler(this, pluginRoot);

//#if DEBUG
            // Search for plugins in worldwind.exe (plugin development/debugging aid)
            compiler.FindPlugins(Assembly.GetExecutingAssembly());
//#endif
　　　　　　 //从启动文件夹下Plugins文件夹，加载插件
            compiler.FindPlugins();
　　　　　　//加载启动插件插件
            compiler.LoadStartupPlugins();
        }

　　4.加载启动插件函数的代码

/// Loads the plugins that are set for load on world wind startup.
        /// </summary>
        public void LoadStartupPlugins()
        {
            foreach(PluginInfo pi in m_plugins)
            {
                if(pi.IsLoadedAtStartup)
                {
                    try
                    {
                        // Compile
                        Log.Write(Log.Levels.Debug, LogCategory, "loading "+pi.Name+" ...");
                        worldWind.SplashScreen.SetText("Initializing plugin " + pi.Name);
　　　　　//Load（）方法加载插件，Plugin类的Load()为虚方法，实质上调用的是各个插件重载后的Load()方法
                        Load(pi);
                    }
                    catch(Exception caught)
                    {
                        // Plugin failed to load
                        string message = "Plugin " + pi.Name + " failed: " + caught.Message;
                        Log.Write(Log.Levels.Error, LogCategory, message);
                        Log.Write(caught);

                        // Disable automatic load of this plugin on startup
                        pi.IsLoadedAtStartup = false;

                        worldWind.SplashScreen.SetError(message);
                    }
                }
            }
        }

　　5.现在看两个插件类重载的Load()方法的实例。例如：Compass3D.cs和TimeController.cs。

　　Compass3D.cs的Load()方法

 21行     public override void Load()
        {
            m_menuItem = new System.Windows.Forms.MenuItem("Compass");
            m_menuItem.Click += new EventHandler(m_menuItem_Click);
            m_menuItem.Checked = World.Settings.ShowCompass;
            ParentApplication.ToolsMenu.MenuItems.Add(m_menuItem);
            
            m_form = new FormWidget("Compass");
            m_form.ClientSize = new System.Drawing.Size(200, 200);
            m_form.Location = new System.Drawing.Point(0, 400);
            m_form.BackgroundColor = World.Settings.WidgetBackgroundColor;
            m_form.AutoHideHeader = true;
            m_form.VerticalScrollbarEnabled = false;
            m_form.HorizontalScrollbarEnabled = false;
            m_form.BorderEnabled = false;
　　　　　　　//注册两个窗体事件
            m_form.OnResizeEvent += new FormWidget.ResizeHandler(m_form_OnResizeEvent);
            m_form.OnVisibleChanged += new VisibleChangedHandler(m_form_OnVisibleChanged);
            //实例化Compass3DWidget
            m_compass = new Compass3DWidget();
            m_compass.Location = new System.Drawing.Point(5, 0);
            m_compass.Font = new System.Drawing.Font("Ariel", 10.0f, System.Drawing.FontStyle.Bold);
            m_compass.ParentWidget = m_form;
            m_form_OnResizeEvent(m_form, m_form.WidgetSize);
            
            m_form.ChildWidgets.Add(m_compass);
            m_form.Visible = World.Settings.ShowCompass;
//将要绘制的Widget加载到DrawArgs.NewRootWidget.ChildWidgets，为了在WorldWindow.cs的Render()方法里渲染
            DrawArgs.NewRootWidget.ChildWidgets.Add(m_form);
　　　　　　　//Compass 3D工具菜单按钮
            m_toolbarItem = new WorldWind.NewWidgets.WidgetMenuButton(
                    "Compass 3D",
                    basePath + "\\Data\\Icons\\Interface\\compass2.png",
                    m_form);
　　　　　　//向MenuBar中添加Compass 3D菜单按钮
            ParentApplication.WorldWindow.MenuBar.AddToolsMenuButton(m_toolbarItem);
            base.Load();
        }

　　TimeController.cs的Load方法，如下：

时间控制
public override void Load()
        {
            try
            {
                m_window = new WorldWind.NewWidgets.FormWidget("Time Control");
                m_window.Name = "Time Control";
                m_window.ClientSize = new System.Drawing.Size(300, 183);

                // Bug in FormWidget required anchor to be set before Location and parent widget
                m_window.Anchor = WorldWind.NewWidgets.WidgetEnums.AnchorStyles.Left | WorldWind.NewWidgets.WidgetEnums.AnchorStyles.Bottom;
                m_window.ParentWidget = DrawArgs.NewRootWidget;
                m_window.Location = new System.Drawing.Point(0, DrawArgs.NewRootWidget.ClientSize.Height - 183);
                m_window.Text = "Double Click to Re-Open";
                m_window.BorderEnabled = false;
                m_window.AutoHideHeader = true;
                m_window.BackgroundColor = System.Drawing.Color.FromArgb(0, 0, 0, 0);
                m_window.HeaderEnabled = true;
                m_window.Visible = false;

                time = new WorldWind.NewWidgets.PictureBox();
                time.Name = "Time";
                time.ImageUri = basePath + "\\Data\\Icons\\Time\\time off.png";
                time.ClientLocation = new System.Drawing.Point(12, 59);
                time.ClientSize = new System.Drawing.Size(42, 42);
                time.Visible = true;
                time.ParentWidget = m_window;
                time.OnMouseEnterEvent += new EventHandler(time_OnMouseEnterEvent);
                time.OnMouseLeaveEvent += new EventHandler(time_OnMouseLeaveEvent);
                time.OnMouseUpEvent += new MouseEventHandler(time_OnMouseUpEvent);
                time.CountHeight = false;
                time.CountWidth = true;
                m_window.ChildWidgets.Add(time);

                play = new WorldWind.NewWidgets.PictureBox();
                play.Name = "Play";
                if (TimeKeeper.Enabled)
                {
                    play.ImageUri = basePath + "\\Data\\Icons\\Time\\play on.png";
                }
                else
                {
                    play.ImageUri = basePath + "\\Data\\Icons\\Time\\play off.png";
                }
                play.ClientLocation = new System.Drawing.Point(50, 1);
                play.ClientSize = new System.Drawing.Size(82, 82);
                play.Visible = true;
                play.ParentWidget = m_window;
                play.OnMouseEnterEvent += new EventHandler(play_OnMouseEnterEvent);
                play.OnMouseLeaveEvent += new EventHandler(play_OnMouseLeaveEvent);
                play.OnMouseUpEvent += new System.Windows.Forms.MouseEventHandler(play_OnMouseUpEvent);
                play.CountHeight = true;
                play.CountWidth = true;
                m_window.ChildWidgets.Add(play);

                close = new WorldWind.NewWidgets.PictureBox();
                close.Name = "Close";
                close.ImageUri = basePath + "\\Data\\Icons\\Time\\close off.png";
                close.ClientLocation = new System.Drawing.Point(29, 3);
                close.ClientSize = new System.Drawing.Size(22, 22);
                close.Visible = true;
                close.ParentWidget = m_window;
                close.OnMouseEnterEvent += new EventHandler(close_OnMouseEnterEvent);
                close.OnMouseLeaveEvent += new EventHandler(close_OnMouseLeaveEvent);
                close.OnMouseUpEvent += new MouseEventHandler(close_OnMouseUpEvent);
                close.CountHeight = false;
                close.CountWidth = false;
                m_window.ChildWidgets.Add(close);

                rewind = new WorldWind.NewWidgets.PictureBox();
                rewind.Name = "Rewind";
                rewind.ImageUri = basePath + "\\Data\\Icons\\Time\\repeat off.png";
                rewind.ClientLocation = new System.Drawing.Point(16, 26);
                rewind.ClientSize = new System.Drawing.Size(32, 32);
                rewind.Visible = true;
                rewind.ParentWidget = m_window;
                rewind.OnMouseEnterEvent += new EventHandler(rewind_OnMouseEnterEvent);
                rewind.OnMouseLeaveEvent += new EventHandler(rewind_OnMouseLeaveEvent);
                rewind.OnMouseUpEvent += new MouseEventHandler(rewind_OnMouseUpEvent);
                rewind.CountHeight = false;
                rewind.CountWidth = false;
                m_window.ChildWidgets.Add(rewind);

                pause = new WorldWind.NewWidgets.PictureBox();
                pause.Name = "Pause";
                if (TimeKeeper.Enabled)
                {
                    pause.ImageUri = basePath + "\\Data\\Icons\\Time\\pause off.png";
                }
                else
                {
                    pause.ImageUri = basePath + "\\Data\\Icons\\Time\\pause on.png";
                }
                pause.ClientLocation = new System.Drawing.Point(35, 88);
                pause.ClientSize = new System.Drawing.Size(64, 64);
                pause.Visible = true;
                pause.ParentWidget = m_window;
                pause.OnMouseEnterEvent += new EventHandler(pause_OnMouseEnterEvent);
                pause.OnMouseLeaveEvent += new EventHandler(pause_OnMouseLeaveEvent);
                pause.OnMouseUpEvent += new System.Windows.Forms.MouseEventHandler(pause_OnMouseUpEvent);
                pause.CountHeight = true;
                pause.CountWidth = false;
                m_window.ChildWidgets.Add(pause);

                slow = new WorldWind.NewWidgets.PictureBox();
                slow.Name = "Slow";
                slow.ImageUri = basePath + "\\Data\\Icons\\Time\\slow off.png";
                slow.ClientLocation = new System.Drawing.Point(97, 88);
                slow.ClientSize = new System.Drawing.Size(64, 64);
                slow.Visible = true;
                slow.ParentWidget = m_window;
                slow.OnMouseEnterEvent += new EventHandler(slow_OnMouseEnterEvent);
                slow.OnMouseLeaveEvent += new EventHandler(slow_OnMouseLeaveEvent);
                slow.OnMouseUpEvent += new System.Windows.Forms.MouseEventHandler(slow_OnMouseUpEvent);
                slow.CountHeight = false;
                slow.CountWidth = false;
                m_window.ChildWidgets.Add(slow);

                fast = new WorldWind.NewWidgets.PictureBox();
                fast.Name = "Fast";
                fast.ImageUri = basePath + "\\Data\\Icons\\Time\\fast off.png";
                fast.ClientLocation = new System.Drawing.Point(158, 88);
                fast.ClientSize = new System.Drawing.Size(64, 64);
                fast.Visible = true;
                fast.ParentWidget = m_window;
                fast.OnMouseEnterEvent += new EventHandler(fast_OnMouseEnterEvent);
                fast.OnMouseLeaveEvent += new EventHandler(fast_OnMouseLeaveEvent);
                fast.OnMouseUpEvent += new System.Windows.Forms.MouseEventHandler(fast_OnMouseUpEvent);
                fast.CountHeight = false;
                fast.CountWidth = false;
                m_window.ChildWidgets.Add(fast);

                timeLabel = new WorldWind.NewWidgets.TextLabel();
                timeLabel.Name = "Current Time";
                timeLabel.ClientLocation = new System.Drawing.Point(134, 65);
                timeLabel.ClientSize = new System.Drawing.Size(140, 60);
                timeLabel.Visible = true;
                timeLabel.ParentWidget = m_window;
                timeLabel.Text = GetCurrentTimeString();
                TimeKeeper.Elapsed += new System.Timers.ElapsedEventHandler(TimeKeeper_Elapsed);
                timeLabel.CountHeight = false;
                timeLabel.CountWidth = true;
                timeLabel.WordBreak = true;
                m_window.ChildWidgets.Add(timeLabel);

                DrawArgs.NewRootWidget.ChildWidgets.Add(m_window);

                m_toolbarItem = new WorldWind.NewWidgets.WidgetMenuButton(
                    "Time Controller",
                    basePath + "\\Data\\Icons\\Time\\time off.png",
                    m_window);
　　　　　　//向MenuBar中添加菜单按钮
                ParentApplication.WorldWindow.MenuBar.AddToolsMenuButton(m_toolbarItem);
            }
            catch (Exception ex)
            {
                Log.Write(ex);
            }
            base.Load();
        }

其他插件的重载后的Load()方法也是类似的，不再赘述。希望能帮研究WW的朋友理清插件加载过程的思路，少走弯路。

其他部分：

WorldWind学习系列四：功能分析——Show Planet Axis、Show Position 、Show Cross Hairs功能

WorldWind学习系列三：简单功能分析——主窗体的键盘监听处理及拷贝和粘贴位置坐标功能

WorldWind学习系列三：功能分析——截屏功能和“关于”窗体分析

WorldWind学习系列二：擒贼先擒王篇2

WorldWind学习系列二：擒贼先擒王篇1

WorldWind学习系列一：顺利起航篇