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

Caliburn.Micro学习笔记目录

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： CaliburnIHandle.rar

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
<Window x:Class="CaliburnIHandle.MyViews.MyMainView"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/PResentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        Title="MyMainView" Height="300" Width="300">    <StackPanel>        <TextBox x:Name="StrMessage" Margin="5"/>        <Button x:Name="OpenOneWin" Content="OpenOneWin" Margin="5"/>               <Button Content="Publish" x:Name="Publish" Margin="5"/>    </StackPanel></Window>
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<string>,IHandle<MyMessage>    {        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
<UserControl x:Class="CaliburnIHandle.MyViews.OneCView"             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"              mc:Ignorable="d"                           Height="300" Width="300">    <StackPanel>        <TextBlock FontSize="13" HorizontalAlignment="Center">1</TextBlock>        <TextBox Margin="5" x:Name="OneMessage"></TextBox>        <Button Margin="5" x:Name="OnePublish" Content="Publish"/>    </StackPanel></UserControl>
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<string>    {        readonly IEventAggregator _event;        string oneMessage;        public string OneMessage        {            get            {                return oneMessage;            }            set            {                oneMessage = value;                NotifyOfPropertyChange(() => OneMessage);            }        }        public OneCViewModel()        {            _event = IoC.Get<IEventAggregator>();            _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<TMessage> : IHandle {  //don't use contravariance here        /// <summary>        ///   Handles the message.        /// </summary>        /// <param name = "message">The message.</param>        void Handle(TMessage message);    }
IHandle<T>只有一个处理T事件的的方法
EventAggregator类通过
 /// <summary>        ///   Subscribes an instance to all events declared through implementations of <see cref = "IHandle{T}" />        /// </summary>        /// <param name = "subscriber">The instance to subscribe for event publication.</param>        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
       /// <summary>        ///   Publishes a message.        /// </summary>        /// <param name = "message">The message instance.</param>        /// <remarks>        ///   Does not marshall the the publication to any special thread by default.        /// </remarks>        public virtual void Publish(object message) {            if (message == null) {                throw new ArgumentNullException("message");            }            Publish(message, PublicationThreadMarshaller);        }        /// <summary>        ///   Publishes a message.        /// </summary>        /// <param name = "message">The message instance.</param>        /// <param name = "marshal">Allows the publisher to provide a custom thread marshaller for the message publication.</param>        public virtual void Publish(object message, Action<System.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));                    }                }            });        }