Caliburn.Micro学习笔记(三)----事件聚合IEventAggregator和 Ihandle<T>-白红宇

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今天说一下Caliburn.Micro的IEventAggregator和IHandle<T>分成两篇去讲这一篇写一个简单的例子

看一它的的实现和源码

下一篇用它们做一个多语言的demo

这两个是事件的订阅和广播，很强大，但用的时候要小心发生不必要的冲突。

先看一下它的实现思想

在Caliburn.Micro里EventAggregator要以单例的形式出现这样可以做到对广播做到统一的管理

对象实现IHand<T>接口后通过EventAggregator的subsribe方法把自己加入到Handler集合中这样就能接叫信息

能过EventAggregator.Publish(object obj)方法去发送广播

源码：

先看一下个小demo再去分析它的源码是怎么实现的

效果

先写一个消息类，这个类只是做一个IHandle<T>的类型应用没有什么实际意义

class MyMessage    {        public string Str        {            get;            set;        }        public override string ToString()        {            return Str;        }    }

建一个窗体MainView和一个ViewModel类

窗体有一个textBox显示消息。一个button打开窗体一个发布消息

再看一下ViewModel

实现了两个IHandle<T> 一个是string 类型一个是我们自己定义的MyMessage

MainViewMode发布string类型的广播也接收string类型和MyMessage类型的消息

[Export(typeof(IShell))]    class MyMainViewModel : PropertyChangedBase, IHandle
              
               ,IHandle
               
                    {        readonly IEventAggregator _events;        readonly IWindowManager _windowManager;        string strMessage;        public string StrMessage        {            get            {                return strMessage;            }            set            {                strMessage = value;                NotifyOfPropertyChange(() => StrMessage);            }        }               [ImportingConstructor]        public MyMainViewModel(IEventAggregator e,IWindowManager win)        {            _events = e;            _events.Subscribe(this);            _windowManager = win;        }        public void Handle(string message)        {            StrMessage = message;        }        public void Handle(MyMessage message)        {            StrMessage = message.ToString();        }        #region         public void Publish()        {            _events.Publish(StrMessage);        }        #endregion        #region 打开窗体        public void OpenOneWin()        {            OneCViewModel _one=new OneCViewModel();            _windowManager.ShowWindow(_one);        }        #endregion

再建一个窗体做接收和广播

它只接收string类型的消息和发布MyMessage类型的消息

using Caliburn.Micro;using CaliburnIHandle.CommonC;using System;using System.Collections.Generic;using System.ComponentModel.Composition;using System.Linq;using System.Text;namespace CaliburnIHandle.MyViewModels{    [Export(typeof(OneCViewModel))]    class OneCViewModel : PropertyChangedBase, IHandle
              
                   {        readonly IEventAggregator _event;        string oneMessage;        public string OneMessage        {            get            {                return oneMessage;            }            set            {                oneMessage = value;                NotifyOfPropertyChange(() => OneMessage);            }        }        public OneCViewModel()        {            _event = IoC.Get
               
                ();            _event.Subscribe(this);        }        public void OnePublish()        {            _event.Publish(new MyMessage { Str = OneMessage + " One!" });        }        public void Handle(string message)        {            OneMessage = message;        }    }}

这是一个很简单的例子我们看一下Caliburn.Micro源码它是怎么实现的

看一下IHandle<T>接口

public interface IHandle
              
                : IHandle {  //don't use contravariance here        /// 
                       ///   Handles the message.        /// 
        /// 
               The message.        void Handle(TMessage message);    }

IHandle<T>只有一个处理T事件的的方法

EventAggregator类通过

///         ///   Subscribes an instance to all events declared through implementations of 
                       /// 
        /// The instance to subscribe for event publication.        public virtual void Subscribe(object subscriber) {            if (subscriber == null) {                throw new ArgumentNullException("subscriber");            }            lock(handlers) {                if (handlers.Any(x => x.Matches(subscriber))) {                    return;                }                handlers.Add(new Handler(subscriber));            }        }

把订阅的类放到Handlers集合里

再通过Publish发布相应的消息

///         ///   Publishes a message.        /// 
        /// The message instance.        /// 
              
                       ///   Does not marshall the the publication to any special thread by default.        /// 
                      public virtual void Publish(object message) {            if (message == null) {                throw new ArgumentNullException("message");            }            Publish(message, PublicationThreadMarshaller);        }        ///         ///   Publishes a message.        /// 
        /// The message instance.        /// Allows the publisher to provide a custom thread marshaller for the message publication.        public virtual void Publish(object message, Action
              
                marshal) {            if (message == null){                throw new ArgumentNullException("message");            }            if (marshal == null) {                throw new ArgumentNullException("marshal");            }            Handler[] toNotify;            lock (handlers) {                toNotify = handlers.ToArray();            }            marshal(() => {                var messageType = message.GetType();                var dead = toNotify                    .Where(handler => !handler.Handle(messageType, message))                    .ToList();                if(dead.Any()) {                    lock(handlers) {                        dead.Apply(x => handlers.Remove(x));                    }                }            });        }

本文转自lpxxn博客园博客，原文链接：http://www.cnblogs.com/li-peng/p/3431035.html，如需转载请自行联系原作者