We will create a button in a Group, and listen the button click event(MouseEvent.Click):

		protected function windowedapplication1_creationCompleteHandler(event:FlexEvent):void {
			//  Create button and container
			var hbox:HGroup = new HGroup();
			var button:Button = new Button();
			button.label = "Button";

			// Add Eventer litener
			button.addEventListener(MouseEvent.CLICK, onButtonClick1);
			button.addEventListener(MouseEvent.CLICK, onButtonClick2);
			hbox.addEventListener(MouseEvent.CLICK, onButtonClick3);

			hbox.addElement(button);
			addElement(hbox);
		}

			// Button click handler 1
			private function onButtonClick1(e:MouseEvent):void {
				e.stopImmediatePropagation(); // or e.stopPropagation();
				trace("Handler 1");
			}

			// Button click handler 2
			private function onButtonClick2(e:MouseEvent):void {
				trace("Handler 2");
			}

			// Button click handler 3 listened by hbox
			private function onButtonClick3(e:MouseEvent):void {
				trace("Handler 3");
			}

Here is the difference:

when use stop propagation in the handler 1st, the trace is:

Handler 1
Handler 2

but when use stopImmediatePropagation(), the trace is:

Handler 1

That’s pretty easy to find the differences:

“The stopImmediatePropagation() method also prevents the Event objects from moving on to the next node, but it does not allow any other event listeners on the current node to execute.” (Adobe livedocs)

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情况是这样的:
自定义Event: EventTest: 继承Event, 增加了一些属性, 重写了toString(), 未重写Clone.

出现问题: 创建EventTest实例后, 多次监听并转发, 在监听, 转发过程中, Event实例对象被Clone, 因为未重写Clone方法, 会通过Event类的Clone方法进行复制, 仅会复制其EventType, 且类型为Event.

形象的说就是: eventTest –> 被监听到, 准发 ->框架Clone eventTest(EventTest类中未重写Clone方法, 于是eventTest被克隆为一个普通Event) –> 再次监听, Event类型不吻合, 报错.

公司代码规范中严格规定了自定义Event必须及时重写Clone与toString方法, 写了这么久, 我才领悟到原因. 败了

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中文API: http://www.adobe.com/livedocs/flex/3_cn/mx/events/StateChangeEvent.html

使用方法:

1. ActionScript中监听Event

ui.addEventListener(StateChangeEvent.CURRENT_STATE_CHANGE, onCurrentStateChange);

注意: 如果用在主程序Application creationComplete的响应方法中, 可能无法监听首个StateChange事件(进入初始State);

2. MXML中监听Event

currentStateChange="onCurrentStateChange(event)"

附录: 响应函数

/** On State Change . */
protected function onCurrentStateChange(event:StateChangeEvent):void {
	printLog("LastState: " + event.oldState + "; currentState" + currentState);
}

Trace信息:

LastState: StateEmployeesList; currentStateStateDeptMgt

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/** * Dispatched when …. * @eventType com.events.MyEvent.EVENT_TEST */
[Event(name=”myEvent” type=”com.events.MyEvent”)]

在使用new testr().addEvent…时提示的Const是错误的.MyEvent.MY_EVENT

解决方法:

[Event(name=”eventTest” type=”com.events.myevent”)]
此时的提醒为MyEvent.EVENT_TEST
[]中的name应与Event中的const的名字 如EVENT_TEST:String = "myEvent"; 中的EVENT_TEST对应 ,’_"后的字母保留大写去掉下划线->eventTest即可.

注意: Flex框架中的事件， 其Const 与String的name都是想对应的.

==>不得不承认 这样子比较挫<==

所以在编写自定义事件时, 最好也遵守这个不成文的规定:

public static const EVENT_EO_EDITOR:String = "eventEoEditor";

而不是随便乱写一个String, 这样便于在其他派发该事件的类中编写事件注释.

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1.弱智级别:*****  隔着锅台上炕:  没有dispatch就addEventListener

2.弱智级别:****   驴唇不对马嘴:  addEventListener中Event类型不符
3.弱智级别:***    驴唇不对马嘴:   Listener参数中Event类型不符[FleBuilder会在编译时报错]
4.弱智级别**      脑子让驴踢了:   在addEventListener之前就dispatch Event[不太容易发现]

自定义事件常见错误:

1. Type不使用Const的String

2. 构造函数中super(type…)中type填写错误.

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作者:http://liguoliang.com 欢迎访问:Adobe上海用户组: http://riashanghai.com ]

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,则应事先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.
需要注意的是, 如果事件派发者属性为Public, 则在任何允许的地方都可以增加监听函数, 从而达到低内聚, 更易于操作.

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);

}

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