帮忙注释一下代码解决方案

package{
import flash.events.*;
public class Thermometer extends EventDispatcher{
private var _temp:Number=32;//温度
public static const TEMP_CHANGED:String="tempChanged";//温度改变事件

//设置温度
public function set temp(newTemp:Number):void{
_temp=newTemp;
trace("Fired TEMP_CHANGED event");
dispatchEvent(new Event(TEMP_CHANGED));//派发温度改变事件
}

//获取温度
public function get temp():Number{
return _temp;
}
}
}

package{
import Thermometer;
import flash.events.*;
public class TempDisplay{
public function TempDisplay(thermometer:Thermometer){
    //监听温度改变事件
thermometer.addEventListener(Thermometer.TEMP_CHANGED,onTempChanged);
}
//温度改变后进行处理
protected function onTempChanged(event:Event):void{
var thermometer:Thermometer=Thermometer(event.target);
trace(thermometer.temp+"F");
}
}
}

package{
import flash.display.*;
public class TemperatureMonitor extends Sprite{
protected var thermometer:Thermometer;
protected var tempDisplayF:TempDisplay;
public function TemperatureMonitor(){
thermometer=new Thermometer();
tempDisplayF=new TempDisplay(thermometer);
thermometer.temp=57;
thermometer.temp=98.6;
thermometer.temp=-12;
}
}
}

------解决方案--------------------

thermometer这是一个对象，event.target当前操作对象