How can I press keyboard to play vdo only once!

Question

Hi, I'm here again for your help :{ I have a question which I tried to google it but can't find the answer. Well,..May be there is an answer but I just can't make it works? I'm in a process of learning AS3 so let's say I'm still new here.
What I'm doing is making a keyboatd to respond with the vdo files I have. It is a very simple idea as press-n-play. Each keys has their vdos to play and if you press another button while the first one is still pressing, it'll play another vdo of its key. I have make this as boolean with function of keydown and keyup like this:
import flash.events.Event;
import flash.events.KeyboardEvent;
import flash.net.NetStream;
import flash.net.NetConnection;
import flash.media.Video;
var isLeft:Boolean = false;
var isRight:Boolean = false;
var video;
var nc;
var ns;
stage.addEventListener(KeyboardEvent.KEY_DOWN,onDown);
stage.addEventListener(KeyboardEvent.KEY_UP,onUP);
this.addEventListener(Event.ENTER_FRAME,playVid);
                    nc = new NetConnection();
                    nc.connect(null);
                    ns = new NetStream(nc);
                    ns.client = this;
                    video = new Video(550,400);
                    addChild(video);
                    video.attachNetStream(ns);
function onDown(e:KeyboardEvent):void
          switch (e.keyCode)
                    case 37 :
                              //ns.play("TomAndJerry.flv");
                              isLeft=true;
                              break;
                    case 39 :
                              //ns.play("westler.flv");
                              isRight = true;
                              break;
function onUP(e:KeyboardEvent):void
          switch (e.keyCode)
                    case 37 :
                              isLeft = false;
                              break;
                    case 39 :
                              isRight = false;
                              break;
function playVid(e:Event):void
          if (isLeft)
                    trace("kk");
                    ns.play("westler.flv");
                    isLeft = false;
          else if (isRight)
                    trace("PP");
                    ns.play("TomAndJerry.flv");
                    //isRight = false;
I have tried making a keydown function without using any boolean or those true of false things to just play a vdo. It worked but, I still have the same problem that I can't find a solution which is ....
When you hold down the keyboard button the vdo will keep start at the beginning.
All I want is to play the vdo even the key is press down. If the vdo ends then play again as loop but if the key is up the vdo will play until it ends.
And  if there are more than one button are holding down just play the vdo of the lastest pressed button.
T-T"
Thanks.
Ps. I have tried removeEventListener but, it made every buttons' function gone.

Answer 1

Wow! That is the problem like you said.
I have removed it out and try this:
function onDown(e:KeyboardEvent):void
          if (e.keyCode==49)
                    ns.play("GetThere.flv");
                    stage.removeEventListener(KeyboardEvent.KEY_DOWN,onDown);
                    onUP(null);
          if (e.keyCode==69)
                    ns.play("westler.flv");
                    stage.removeEventListener(KeyboardEvent.KEY_DOWN,onDown);
                    onUP(null);
function onUP(e:KeyboardEvent):void
          if(e.keyCode==49)
                    stage.addEventListener(KeyboardEvent.KEY_DOWN,onDown);
          if(e.keyCode==69)
                    stage.addEventListener(KeyboardEvent.KEY_DOWN,onDown);
And it works!
But, then I have an error massage says "
TypeError: Error #1009: Cannot access a property or method of a null object reference.
          at xxx_fla::MainTimeline/onUP()
          at xxx_fla::MainTimeline/onDown()"
May I ask you something?
Will it make me any problem if I load more vdos? Let's say about...20?
Because if it is hard to solve this error and it won't make anything worse (time delay,etc.) then I'm fine with it.
Thanks :}