我正在尝试删除使用addChild添加到场景中的图形'lose_mc'。
当用户单击下一个level_btn时尝试使用removeChild时，会出现此错误：
TypeError: Error #2007: Parameter listener must be non-null.
at flash.events::EventDispatcher/removeEventListener()
at Function/<anonymous>()
任何人都有任何想法为什么这不起作用？这是我的代码。 **
import flash.net.URLRequest;
import flash.display.MovieClip;
import fl.transitions.Tween;
import fl.transitions.easing.*;
import flash.events.MouseEvent;
import flash.events.Event;
import flash.events.Event;
import flash.display.Loader;
stop();
//stage.removeEventListener(Event.ENTER_FRAME, nextButtonClick);
var hitObstacle:Boolean=false;
var points=2; //The points will be set at 2
points_txt.text=points.toString(); //Health will be displayed in points_txt box
var lose_mc = new lose();
var win_mc = new win();
//crowhit_mc.visible=false;
var loader:Loader = new Loader()
addChild(loader);
//var url:URLRequest = new URLRequest("test.swf");
//var lose_mc = new lose();
//var win_mc = new win();
//var hitObstacle:Boolean=false;
var leafArray:Array = new Array(leaf01,leaf02,leaf03);
var leafsOnstage:Array = new Array();
var leafsCollected:int = 0;
var leafsLost:int = 0;
for (var i:int = 0; i<20; i++) {
var pickLeaf = leafArray[int(Math.random() * leafArray.length)];
var leaf:MovieClip = new pickLeaf();
addChild(leaf);
leaf.x = Math.random() * stage.stageWidth-leaf.width;// fruit.width is subtracted from the random x position to elimate the slight possibility that a clip will be placed offstage on the right.
leaf.y = Math.random() * -500;
leaf.speed = Math.random() * 15 + 5;
leafsOnstage.push(leaf);
}
basket_mc.addEventListener(MouseEvent.MOUSE_DOWN, dragBasket);
stage.addEventListener(MouseEvent.MOUSE_UP, dragStop);
function dragBasket(e:Event):void {
basket_mc.startDrag();
}
function dragStop(e:Event):void {
basket_mc.stopDrag();
}
stage.addEventListener(Event.ENTER_FRAME, catchLeaf);
function catchLeaf(e:Event):void {
for (var i:int = leafsOnstage.length-1; i > -1; i--) {
var currentLeaf:MovieClip = leafsOnstage[i];
currentLeaf.y += currentLeaf.speed;
if (currentLeaf.y > stage.stageHeight - currentLeaf.height) {
currentLeaf.y = 0 - currentLeaf.height;
leafsLost++;
field2_txt.text = "Total Leaves Lost: " + leafsLost;
}
if (currentLeaf.hitTestObject(basket_mc)) {
leafsCollected++;
removeChild(currentLeaf);
leafsOnstage.splice(i,1);
field1_txt.text = "Total Leaves Collected: " + leafsCollected;
if (leafsCollected >= 20) {
basket_mc.gotoAndStop(20);
} else if (leafsCollected > 15) {
basket_mc.gotoAndStop(15);
} else if (leafsCollected>10) {
basket_mc.gotoAndStop(10);
} else if (leafsCollected>5) {
basket_mc.gotoAndStop(5);
}
}
}
if (leafsOnstage.length <= 0) {
field1_txt.text = "You Win! You have collected enough leaves for the day.";
nextlevel_btn.addEventListener(Event.ENTER_FRAME, fl_FadeSymbolINwin);
nextlevel_btn.alpha = 0;
function fl_FadeSymbolINwin(event:Event)
{
nextlevel_btn.alpha += 0.01;
if(nextlevel_btn.alpha >= 1)
{
nextlevel_btn.removeEventListener(Event.ENTER_FRAME, fl_FadeSymbolIn);
}
}
field2_txt.text = "";
stage.removeEventListener(Event.ENTER_FRAME, catchLeaf);
var win_mc = new win();
win_mc.x = 215.70;
win_mc.y = 163.25;
win_mc.w = 100;
win_mc.h = 145;
addChild(win_mc);
removeChild(crow_mc);
}
if (leafsLost >= 20) {
field1_txt.text = "Sorry you lose. You have lost too many leaves!";
restart_btn.addEventListener(Event.ENTER_FRAME, fl_FadeSymbolIn);
restart_btn.alpha = 0;
function fl_FadeSymbolIn(event:Event)
{
restart_btn.alpha += 0.01;
if(restart_btn.alpha >= 1)
{
restart_btn.removeEventListener(Event.ENTER_FRAME, fl_FadeSymbolIn);
}
}
field2_txt.text = "";
stage.removeEventListener(Event.ENTER_FRAME, catchLeaf);
for (var j:int = leafsOnstage.length-1; j > -1; j--) {
currentLeaf = leafsOnstage[j];
removeChild(currentLeaf);
leafsOnstage.splice(j,1);
lose_mc.x = 215.70;
lose_mc.y = 163.25;
lose_mc.w = 100;
lose_mc.h = 145;
addChild(lose_mc); //this is the movieclip in my library im adding it to the screen
}
}
}
//nextlevel_btn.addEventListener(MouseEvent.CLICK, nextButtonClick);
/*restart_btn.addEventListener(MouseEvent.CLICK, buttonClick)
function buttonClick(e:MouseEvent):void
{
try{
loader_mc.unloadAndStop();
} catch(e:Error) {
}
var urlRequest : URLRequest = new URLRequest("test.swf");
loader_mc.load(urlRequest);
removeChild(win_mc);
}
//function nextButtonClick(e:MouseEvent):void{
//removeChild(win_mc);
//loader.unloadAndStop();
//var request:URLRequest = new URLRequest("test.swf");
//loader.load(request);
crow_mc.addEventListener(MouseEvent.CLICK,rotateCrow);
function rotateCrow(e:MouseEvent):void {
crow_mc.rotation +=10;
var myTween:Tween = new Tween(crow_mc, "alpha", Strong.easeOut, 1,10,25, true);
}
*/
var crow_mcSpeedX:int = -6;
var crow_mcSpeedY:int = 2;
stage.addEventListener(Event.ENTER_FRAME, loop);
function loop(evt:Event) {
crow_mc.x += crow_mcSpeedX;
crow_mc.y += crow_mcSpeedY;
//because the ball's position is measured by where its CENTER is...
//...we need add or subtract half of its width or height to see if that SIDE is hitting a wall
//first check the left and right boundaries
if(crow_mc.x <= crow_mc.width/2){ //check if the x position of the left side of the ball is less than or equal to the left side of the screen, which would be 0
crow_mc.x = crow_mc.width/2; //then set the ball's x position to that point, in case it already moved off the screen
crow_mcSpeedX *= -1; //and multiply the ball's x speed by -1, which will make it move right instead of left
} else if(crow_mc.x >= stage.stageWidth-crow_mc.width/2){ //check to see the right side of the ball is touching the right boundary, which would be 550
crow_mc.x = stage.stageWidth-crow_mc.width/2; //reposition it, just in case
crow_mcSpeedX *= -1; //multiply the x speed by -1 (now moving left, not right)
}
//now we do the same with the top and bottom of the screen
if(crow_mc.y <= crow_mc.height/2){ //if the y position of the top of the ball is less than or equal to the top of the screen
crow_mc.y = crow_mc.height/2; //like we did before, set it to that y position...
crow_mcSpeedY *= -1; //...and reverse its y speed so that it is now going down instead of up
} else if(crow_mc.y >= stage.stageHeight-crow_mc.height/2){ //if the bottom of the ball is lower than the bottom of the screen
crow_mc.y = stage.stageHeight-crow_mc.height/2; //reposition it
crow_mcSpeedY *= -1; //and reverse its y speed so that it is moving up now
}
//}
//points--; //Health is decreased by 1 each time a trap_mc is clicked
//points_txt.text=points.toString();
//lose_mc.visible=true;
if (basket_mc.hitTestObject(crow_mc)) { //If the player_mc hits the sharkfin_mc
if (hitObstacle==false){ //Only subtract health if hitObstacle is false
trace("Hit Object")
//crow_mc.visible=false; //crow_mc becomes invisible
//removeChild(leaf);
//leafsOnstage.visable = false;
//lose_mc.x = 215.70;
//lose_mc.y = 163.25;
//lose_mc.w = 100;
//addChild(lose_mc);
points--; //Points are decreased by 1 each time crow_mc is hit - hittestobject()
points_txt.text=points.toString();
}
hitObstacle=true;
}
}
restart_btn.addEventListener(MouseEvent.CLICK, backButtonClick);
function backButtonClick(e:MouseEvent):void{
removeChild(lose_mc);
loader.unloadAndStop();
var request:URLRequest = new URLRequest("test.swf");
loader.load(request);
}
nextlevel_btn.addEventListener(MouseEvent.CLICK, nextButtonClick);
function nextButtonClick(e:MouseEvent):void{
loader.unloadAndStop();
var request:URLRequest = new URLRequest("snowflake.swf");
loader.load(request);
}
**
这是导致问题的代码区域。
**
nextlevel_btn.addEventListener(MouseEvent.CLICK, nextButtonClick);
function nextButtonClick(e:MouseEvent):void{
removeChild(win_mc);
loader.unloadAndStop();
var request:URLRequest = new URLRequest("snowflake.swf");
loader.load(request);
}
**
答案 0 :(得分：3)
这不是导致问题的区域，因为Flash清楚地说：
TypeError: Error #2007: Parameter listener must be non-null.
at flash.events::EventDispatcher/removeEventListener()
at Function/<anonymous>()
我们可以看到，错误发生在removeEventListener
removeEventListener有两个参数：event和listener
我们还可以看到，Flash说：参数listener必须是非空的
这意味着传递给listener的参数removeEventListener为空
您的代码中可能导致错误的部分如下：
if (leafsOnstage.length <= 0) {
field1_txt.text = "You Win! You have collected enough leaves for the day.";
nextlevel_btn.addEventListener(Event.ENTER_FRAME, fl_FadeSymbolINwin);
nextlevel_btn.alpha = 0;
function fl_FadeSymbolINwin(event:Event)
{
nextlevel_btn.alpha += 0.01;
if(nextlevel_btn.alpha >= 1)
{
nextlevel_btn.removeEventListener(Event.ENTER_FRAME, fl_FadeSymbolIn);
}
}
首先，您要添加侦听器fl_FadeSymbolINwin，但删除了另一个侦听器fl_FadeSymbolIn。其次，由于某种原因，您在if块内声明了一个函数。您需要做的是正确地设置代码格式，并使用哪些参数检查removeEventListener的位置和方式。如果需要，追踪它们。
另外，我建议使用TweenLite（甚至TweenNano）进行淡入淡出效果。您不必乱用所有这些EventListeners。您的淡入淡出按钮代码看起来很简单：
TweenNano.to(nextlevel_btn, 0.5, {alpha:1});