Cocos2d-js中的简易MVC框架(三)中介者Mediator

Mediator作为这套MVC框架的核心部分承载了大部分的功能。Mediator主要分三类：DirectorMediator,SceneMediator,LayerMediator。这三类Mediator都是继承自IMediator，IMediator的实现如下：

/***The game.IMediator
@author ituuz
@date 2014-11-18
IView is the mediator of MVC,create your model to extend this class.
In this mediator can get model,current mediator and rootMediator.
*/
game.IMediator = cc.Class.extend({
    ctor:function () { },
   show:function () {
      throw new Error("SubClass not overwrite show function.");
   },
   getCurrMediator:function () {
    var med = game.Facade._directorMediator.currSceneMediator.currLayerMediator;  
    if (med == null) {
         med = game.Facade._directorMediator.currSceneMediator.rootLayerMediator;
      }
      return med;
   },
   getRootMediator:function () {
    return game.Facade._directorMediator.currSceneMediator.rootLayerMediator;
   },
   getModel:function (cls) {
    return game.Facade._modelMap.get(cls);
   },
   //Use this function to send notification.
   send:function (key,obj) {
       game.Notification.send(key,obj);
   }
});

show函数需要它的子类去实现，show的主要作用就是该Mediator被创建时显示的内容。send函数是用来发送消息的。除此之外还有三个get函数，分别是获取当前Mediator、获取RootMediator和获取Model对象。

下面单独介绍继承自Mediator的这三类Mediator的作用。

首先是DirecotorMediator，它主要是来控制场景的创建和销毁。代码实现如下：

/*
The DirectorMediator
18
Control the scene show or hide.
*/
game.DirectorMediator = game.IMediator.extend({
    sceneMediatorStack:null, 
    currSceneMediator:null,
   ctor:function (view) {
    this.currView = view;
      this.sceneMediatorStack = new game.Stack();
   },
   show:function (parent) { },38)">//Open the new scene and destroy the previous.
   showScene:function (mediator) {
    if (this.currSceneMediator 
            && this.currSceneMediator.rootLayerMediator) { 
      this.currSceneMediator.rootLayerMediator._pDispose();
      } 
    if (this.currSceneMediator) { 
      var layMedList = this.currSceneMediator.layerMediatorList;         while (layMedList.size() > 0) {
          var med = layMedList.pop();
          med._pDispose();
         }
      }  
        this.currSceneMediator = mediator;
      this.sceneMediatorStack = new game.Stack();
      this.sceneMediatorStack.push(mediator);
      cc.director.runScene(mediator.currScene);
    },38)">//Open the new scene and push the previous into the stack
   pushScene:function (mediator) {
    this.currSceneMediator = mediator;    
        this.sceneMediatorStack.push(mediator);
      cc.director.pushScene(mediator.currScene);
   },38)">//Pop the current scene to destroy then go to the previous scene.
   popScene:function () {
    var pop = this.sceneMediatorStack.pop();
      var curr = this.sceneMediatorStack.top();
      this.currSceneMediator = curr;
      cc.director.popScene();
   }
});

DirectorMediator除了继承了Mediator的几个函数外，还有几个控制Scene打开和关闭的函数，分别是showScene,pushScene,popScene，都是控制场景打开和关闭的。

然后介绍的是SceneMediator，它主要是控制LayerMediator的生命周期。控制着LayerMediator的创建和销毁。实现如下：

/*The SceneMediator
18
Control the layer show or hide.
*/
game.SceneMediator = game.IMediator.extend({
    currScene:null,
   currLayerMediator:null,
   rootLayerMediator:null,
   layerMediatorList:null,
   ctor:function (view) {
    this.currScene = view;
      this.layerMediatorList = new game.Stack();
   }, 
    show:function (obj) { 
    if (this.currLayerMediator == undefined 
          || this.currLayerMediator == null ) { 
      this.rootLayerMediator.init();
         this.rootLayerMediator.show(this.currScene,obj);
      } else {
         this.currLayerMediator.init();
         this.currLayerMediator.isRoot = false;
         this.currLayerMediator.show(this.currScene,obj);
      }
   },38)">//Setting the root layer 
    rootLayer:function (layerMed) {
    this.rootLayerMediator = layerMed;
   },
   showRoot:function () {
    this.show();
    },38)">//Open the new layer and destroy previous layer.
   showLayer:function (layerMed,obj) {
    this.currLayerMediator = layerMed;
      this.layerMediatorList = new game.Stack();
      this.layerMediatorList.push(layerMed);
      this.show(obj);
   },38)">//Open the new layer and push the previous layer into stack.
   pushLayer:function (layerMed,obj) {
    this.currLayerMediator = layerMed;
      this.layerMediatorList.push(layerMed);
      this.show(obj);
   },
    //Pop the current layer to destroy then go to the previous layer.
   popLayer:function (obj) {
    var layer = this.layerMediatorList.pop();
      layer && layer._pDispose();
      this.currLayerMediator = this.layerMediatorList.top();
      if (this.currLayerMediator) {
         this.currLayerMediator.freshen(obj);
      } else { 
      this.rootLayerMediator.freshen(obj);
      }
   }
});

它同DirectorMediator一样，控制着LayerMediator，并且拥有几个控制它的函数，包括showLayer、pushLayer、popLayer，除此之外他还有个rootLayer和showRoot函数，这两个函数是用来设置和显示场景上的初始Layer的，cocos2dx中场景内必须有Layer才能显示内容，所以这两个函数设置并显示了root layer。同时SceneMediator还重写了show函数，在重写的show函数中初始化了LayerMediator并且调用了LayerMediator的show函数用来显示Layer。

最后我们介绍一下LayerMediator，这个Mediator我们使用的频率最高，同时包含的功能也比较多。先来看代码：

/**************************************************************************
The LayerMediator
@author ituuz
@date 2014-11-18
The layer's logic.
*************************************************************************/
game.LayerMediator = game.IMediator.extend({
    currView:null,
   backBtn:null,
   mask:null,
   isRoot:true,
   ctor:function (view) {
    this.currView = view;
   },
   show:function (parent,obj) {
    if (this.isRoot) return;
    var size = cc.winSize;
      this.mask = new cc.LayerColor(cc.color(0,200),size.width,size.height);
      parent.addChild(this.mask);
      cc.eventManager.addListener({
         event: cc.EventListener.TOUCH_ONE_BY_ONE,
         swallowTouches: true,
         onTouchBegan: this.onTouchBegan 
    },this.mask);
    },
   onTouchBegan:function(touch,event) {
    //Could to do sth.
    return true;
   },
   init:function () {
    throw new Error("SubClass must be overwrite init function and regist event in this function.");
   },
   freshen:function (obj) {
    cc.log("freshen");
   },
   //Use this function to send notification.
  send:function (key,obj) {
    game.Notification.send(key,obj);
   },
   subscrib:function (type,callback,target) {
    game.Notification.subscrib(type,target);
   },
   unsubscrib:function (type,callback) {
    game.Notification.unsubscrib(type,callback);
   },136); font-style:italic">//Switch scene
    showScene:function (sceneMed) {
    game.Facade._directorMediator.showScene(sceneMed);
      game.Facade._directorMediator.currSceneMediator.showRoot();
   },136); font-style:italic">//Push new scen into the stack
  pushScene:function (sceneMed) {
    game.Facade._directorMediator.pushScene(sceneMed);
    game.Facade._directorMediator.currSceneMediator.showRoot();
   },136); font-style:italic">//Pop current scene out of the stack
  popScene:function () {
    game.Facade._directorMediator.popScene();
   },136); font-style:italic">//Switch layer
    showLayer:function (layerMed,obj) {
    game.Facade._directorMediator.currSceneMediator.showLayer(layerMed,obj); 
    },136); font-style:italic">//Push new layer into the stack
  pushLayer:function (layerMed,obj) {
    game.Facade._directorMediator.currSceneMediator.pushLayer(layerMed, 
  //Pop current scene out of the stack
  popLayer:function (obj) {
    game.Facade._directorMediator.currSceneMediator.popLayer(obj);
   },136); font-style:italic">//private 
    _pDispose:function () {
    var that = this;
    that.destroy();
      that.currView.removeFromParent(true);
      that.mask && this.mask.removeFromParent(true);
   },
   destroy:function () {
    throw new Error("SubClass must be overwrite destroy function and delete event in this function.");
   }
});

这里面通用的几个pop、show、push函数就不多说了，主要说一下其他特殊的函数。首先是构造函数，它有一个参数view，这个view就是和这个Mediator对应的Layer，这里保存了个引用，方便使用。然后是重写的show函数，在该函数中的两个参数parent是该layer的父级容器，obj是在打开该Layer时传入的参数。在show里还对打开的Layer进行了模态处理。还有init函数，该函数是在该LayerMediator初始化时调用的，可以在该函数中初始化一些数据，或者注册监听等。然后LayerMediator中还提供了几个消息相关的函数，分别是发送消息send、注册消息subscrib、删除消息注册unsubscrib。还有freshen(obj)函数是在上层Layer关闭时调用的，obj是可以传递的值，在该函数中可以做一些UI刷新的功能。最后比较重要的两个函数都是有关销毁的。destroy函数是必须在子类重写的，在LayerMediator被销毁时调用，_pDispose是私有的函数，负责销毁公有的对象，不能显示调用。

Mediator在MVC中比较重要，除了自身的动能外，还承载了其他几个功能。首先Mediator中持有View对象，可以对View进行显示更新，同时也要响应View上的各种事件。然后Mediator可以注册和发送消息。同时Mediator还可以获取Model对象，进行操作。

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