RIA Shanghai | Adobe上海用户组

Event:

1.事件派发 Dispatching

Flash.events.EventDispacher类提供了事件dispatch函数,如果需要dispatch事件,则应该考虑继承该类或其子类.如果不能继承该类,则应实现IEventDispatcher接口 

2.监听事件 Listening to Events

在监听事件时应首先考虑是否要使用weak referenced.如果事件监听与派发与监听函数有共同的生命周期,则可以使用strong referenced,在其他的大部分情况下,则应使用weak referenced.

Bindable的三种实现方式:

1.使用Event实现.

2.MXML中使用大括号实现.

3.AS中使用ChangeWatcher实现.

Event与Bindable举例:

有一个Person类:

 
package com.insprise 
{ 
    import flash.events.Event; 
    import flash.events.EventDispatcher; 
    import mx.events.PropertyChangeEvent; 

    public class Person extends EventDispatcher 
    { 
        private var _name:String; 
        private var _age:int; 
        private var _desc:String; 
        /** 
         * 构造函数 
         */ 
        public function Person() 
        { 
            super(); 
        }        
        /** 
         * Get&Set Name SetName时dispatch一个PropertyChangeEvent事件 
         */ 
        [Bindable(event="propertyChange")] 
        public function get name():String { 
            trace("Get name: " + _name); 
            return _name; 
        } 
        public function set name(name_:String):void { 
            if(name_ == _name) { 
                return; 
            } 
            var old:String = this._name; 
            this._name = name_; 
            trace("Set Name to: " + name_); 
            dispatchEvent(PropertyChangeEvent.createUpdateEvent(this,"name",old,name_)); 
        } 
        /** 
         * Get&Set age; age被Set的时候会dispatch一个ageChanged事件. 
         */ 
        [Bindable(event="ageChanged")] 
        public function get age():int { 
            trace("Get age: " + _age); 
            return _age; 
        } 
        public function set age(age_:int):void { 
            if(age_ == _age) { 
                return; 
            } 
            var old:int = this._age; 
            this._age = age_; 
            trace("Set Age to: " + age_); 
            dispatchEvent(new Event("ageChanged")); 

        }        
        /** 
         * Get&Set Desc;desc被set时会自动dispatch一个PropertyChangeEvent. 
         */ 
        [Bindable] 
        public function get desc():String { 
            trace("Get desc: " + _desc); 
            return _desc; 
        } 
        public function set desc(desc_:String):void { 
            if(desc_ == _desc) { 
                return; 
            } 
            var old:String = this._desc; 
            this._desc = desc_; 
            trace("Set desc to: " + desc_); 
        }            
    } 
} 

现在我们通过上面提到的三种方式实现Bindable:

1.使用Event Bindable:

 
		import mx.events.PropertyChangeEvent;
		import com.insprise.Person;
	
		var person:Person = new Person();
		
		/**
		 * 监听PropertyChangeEvent与ageChanged事件
		 */ 
		private function init():void {
			person.addEventListener("propertyChange",propertyChangeHandler);
			person.addEventListener("ageChanged",ageChangedHandler);
		}
		
		/**
		 * 通过对PropertyChangeEvent.property判断是name还是desc被监听,更新屏幕
		 */
		private function propertyChangeHandler(e:PropertyChangeEvent):void {
			if(e.property == "name") {
				textArea_Name.text = e.newValue.toString();
			}else if(e.property == "desc") {
				textArea_Desc.text = e.newValue.toString();
			}else {
				return;
			}
			trace("view: " + e.property + " Changed");
		}
		
		/**
		 * set age之后更新屏幕
		 */ 
		private function ageChangedHandler(e:Event):void {
			textArea_Age.text = String(person.age);
		}

2.MXML使用大括号:

3.使用AS中的ChangeWatcher

private function init():void { 
    var nameWatcher:ChangeWatcher; 
    var ageWatcher:ChangeWatcher; 
    var descWatcher:ChangeWatcher;    
    var canWatche:ChangeWatcher; 
    //nameWatcher = BindingUtils.bindProperty(textArea_Name,"text",person,"name"); 
    ChangeWatcher.watch(person,"name",nameSetter); 
    ageWatcher = BindingUtils.bindProperty(textArea_Age,"text",person,String("age")); 
    descWatcher = BindingUtils.bindProperty(textArea_Desc,"text",person,"desc",true); 
} 
private function nameSetter(e:PropertyChangeEvent):void { 
    if(e==null) { 
        return; 
    } 
    textArea_Name.text = e.newValue.toString(); 
    trace("Name Changed by nameSetter on the Event " + e + " to " + e.newValue); 
} 

private function ageSetter(e:Event):void { 
    //textArea_Age.text = String(person.age); 
    trace("Age is setted by ageSetter on the Event " + " to " + person.age);            
}