clear() ne fonctionne pas

Bonjour tous,
J'ai un erase button qui doit supprimer les lignes que j'ai dessinees, mais cela ne fonctionne pas.
voila mon code:

Code:

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import flash.events.MouseEvent;
import flash.display.Sprite;
 
var startX:int;
var startY:int;
var spr:Sprite;
 
init();
 
 
 
 
function init():void {
spr = new Sprite();
this.addChild(spr);
stage.addEventListener(MouseEvent.MOUSE_DOWN, handleMouseDown);
}
function handleMouseDown(e:MouseEvent):void {
startX = mouseX;
startY = mouseY; 
stage.addEventListener(MouseEvent.MOUSE_MOVE, handleMouseMove);
stage.addEventListener(MouseEvent.MOUSE_UP, handleMouseUp);
}
function handleMouseMove(e:MouseEvent):void {
//display line while drawing
spr.graphics.clear();
drawLineFromStartToMouse(spr);
}
function drawLineFromStartToMouse(_spr:Sprite):void {
_spr.graphics.lineStyle(1,0x000000);
_spr.graphics.moveTo(startX,startY);
_spr.graphics.lineTo(mouseX, mouseY);
}
function handleMouseUp(e:MouseEvent):void {
spr.graphics.clear();
//draw the finished line
var completedLine:Sprite = new Sprite();
drawLineFromStartToMouse(completedLine);
this.addChild(completedLine);
 
 
stage.removeEventListener(MouseEvent.MOUSE_MOVE, handleMouseMove);
stage.removeEventListener(MouseEvent.MOUSE_UP, handleMouseUp);
}
 
btnErase.addEventListener(MouseEvent.CLICK, onPlayClick, false, 0, true);
 
function onPlayClick(evt:MouseEvent):void {
 
graphics.clear();
 
}

Merci beaucoup pour votre aide.