Button Disappears from Stage

Question

I’ve created a two buttons in a frame labeled
“child.” The instance name for one button is
“orientationBtn” and the other is
“stepBtn.” When you click on the orientationBtn you are
taken to a frame labeled “orientation” which holds a
puzzle written in AS3. When the puzzle is complete, two more
buttons appear. One button (playAgain) will reset the puzzle to
play again. The other button (noThanks) is a
gotoAndPlay(“child”) so the user can return to the
menu.
If the user presses a certain sequence of buttons –
orientationBtn, completes the puzzle, noThanks they are taken back
to the menu. If s/he then chooses to complete the puzzle again and
presses the same sequence of buttons, the following error message
appears after pressing the noThanks button - TypeError: Error
#1009: Cannot access a property or method of a null object
reference. Interestingly, the null object is that my
“stepBtn” has disappeared from the stage. Any ideas why
this would happen?

Answer 1

Of course. I should have done that initially. Sorry! You will
see that the noThanks button appears in the function
puzzleSolved at the very bottom of the code.
var puzzlePiecesArr:Array;
var puzzlePiecesFound:Array;
var topDepth:Number;
var totalPuzzlePieces:Number;
var correctPuzzlePieces:Number;
var puzzleBmp:BitmapData;
var intervalID:Number;
var threshold:Number;
var imagesArr:Array;
var imageLoader:Loader;
var requestURL:URLRequest;
var puzzleBoardClip:MovieClip;
var holder:MovieClip;
var dontPlayAgain:Button;
var doPlayAgain:Button;
init();
function init(){
dontPlayAgain = new Button();
doPlayAgain = new Button();
puzzleBoardClip = new MovieClip();
addChild(puzzleBoardClip);
totalPuzzlePieces = 8;
imagesArr = new Array("polycom_200.jpg");
puzzlePiecesArr = new Array();
puzzlePiecesFound = new Array();
correctPuzzlePieces = 0;
threshold = 0xFFFFFF;
noThanks.visible = false; //hides button
playAgain.visible = false; // hides button
congrats.visible = false;
/* Create the image Loader */
imageLoader = new Loader();
imageLoader.contentLoaderInfo.addEventListener(Event.COMPLETE,
onLoadImg);
/* Create the URL Request */
var index:Number = Math.floor(Math.random() *
imagesArr.length);
requestURL = new URLRequest(imagesArr[index]);
// Load the image
imageLoader.load(requestURL);
// Setup a holdery mc to hold the puzzle pieces
holder = new MovieClip();
addChild(holder);
function onLoadImg(evt:Event):void{
// Determine the width and height of each puzzle piece.
// Each puzzle consists of 2 columns and 4 rows.
var widthPuzzlePiece:Number = imageLoader.width / 2;
var heightPuzzlePiece:Number = imageLoader.height / 4;
// Draw the image from the movie clip into a BitmapData Obj.
puzzleBmp = new BitmapData(imageLoader.width,
imageLoader.height);
puzzleBmp.draw(imageLoader, new Matrix());
var puzzlePieceBmp:BitmapData;
var x:Number = 0;
var y:Number = 0;
// Loop 8 times to make each piece
for (var i:Number = 0; i < 8; i++)
puzzlePieceBmp = new BitmapData(widthPuzzlePiece,
heightPuzzlePiece);
puzzlePieceBmp.copyPixels(puzzleBmp, new
Rectangle(x,y,widthPuzzlePiece,heightPuzzlePiece), new Point(0,0));
makePuzzlePiece(puzzlePieceBmp, i);
x += widthPuzzlePiece;
if(x >= puzzleBmp.width)
x = 0;
y += heightPuzzlePiece;
makePuzzleBoard(puzzleBmp.width, puzzleBmp.height);
arrangePuzzlePieces();
function makePuzzlePiece(puzzlePiece:BitmapData, index:int){
var puzzlePieceClip:Bitmap = new Bitmap(puzzlePiece);
var tmp2:MovieClip = new MovieClip();
tmp2.addChild(puzzlePieceClip);
tmp2.name = String(index) // Added for Strict Mode
holder.addChild(tmp2);
holder.addEventListener("mouseDown", pieceMove);
holder.addEventListener("mouseUp", pieceMove);
puzzlePiecesArr.push(tmp2);
// This is used to check if the same piece has been placed
puzzlePiecesFound.push(tmp2.name);
function pieceMove(evt:Event):void{
if(evt.type == "mouseDown"){
evt.target.startDrag();
} else if(evt.type == "mouseUp"){
evt.target.stopDrag();
var puzzlePieceIndex:Number = evt.target.name;
// ADDED VV 4.3. Check if droppped inside of the grid
if(evt.target.dropTarget){
var puzzleBoardSpaceIndex:Number =
evt.target.dropTarget.name;
if(puzzlePieceIndex == puzzleBoardSpaceIndex)
var coordinate:Point = new Point(evt.target.dropTarget.x,
evt.target.dropTarget.y);
var coordinateGlobal:Point = new Point();
coordinateGlobal =
puzzleBoardClip.localToGlobal(coordinate);
evt.target.x = coordinateGlobal.x;
evt.target.y = coordinateGlobal.y;
if(puzzlePiecesFound.length != 0)
for(var i:int = 0;i < puzzlePiecesFound.length; i++)
if(puzzlePiecesFound
== puzzlePieceIndex)
puzzlePiecesFound = "Correct";
correctPuzzlePieces++;
if(correctPuzzlePieces == totalPuzzlePieces)
puzzleSolved();
function arrangePuzzlePieces():void
var widthPuzzlePiece:Number = puzzlePiecesArr[0].width;
var heightPuzzlePiece:Number = puzzlePiecesArr[0].height;
var locationArr:Array = new Array();
locationArr.push({x:10, y:125});
locationArr.push({x:10 + widthPuzzlePiece + 5, y:125});
locationArr.push({x:10, y:125 + heightPuzzlePiece + 5});
locationArr.push({x:10 + widthPuzzlePiece + 5, y:125 +
heightPuzzlePiece + 5});
locationArr.push({x:10, y:125 + (heightPuzzlePiece + 5) *
2});
locationArr.push({x:10 + widthPuzzlePiece + 5, y:125 +
(heightPuzzlePiece + 5) * 2});
locationArr.push({x:10, y:125 + (heightPuzzlePiece + 5) *
3});
locationArr.push({x:10 + widthPuzzlePiece + 5, y:125 +
(heightPuzzlePiece + 5) * 3});
var index:Number = 0;
var coordinates:Object;
while(locationArr.length > 0)
coordinates = locationArr.splice(Math.floor(Math.random() *
locationArr.length), 1)[0];
puzzlePiecesArr[index].x = coordinates.x;
puzzlePiecesArr[index].y = coordinates.y;
index++;
function makePuzzleBoard(width:Number, height:Number):void{
var widthPuzzlePiece:Number = width / 2;
var heightPuzzlePiece:Number = height / 4;
var puzzleBoardSpaceClip:MovieClip;
var x:Number = 0;
var y:Number = 0;
for(var i:Number = 0; i < 8; i++)
puzzleBoardSpaceClip = new MovieClip();
puzzleBoardSpaceClip.graphics.lineStyle(0);
puzzleBoardSpaceClip.graphics.beginFill(0xFFFFFF,100);
puzzleBoardSpaceClip.graphics.lineTo(widthPuzzlePiece,0);
puzzleBoardSpaceClip.graphics.lineTo(widthPuzzlePiece,heightPuzzlePiece);
puzzleBoardSpaceClip.graphics.lineTo(0,heightPuzzlePiece);
puzzleBoardSpaceClip.graphics.lineTo(0,0);
puzzleBoardSpaceClip.graphics.endFill();
puzzleBoardSpaceClip.x = x;
puzzleBoardSpaceClip.y = y;
x += widthPuzzlePiece;
if(x >= width)
x = 0;
y += heightPuzzlePiece;
puzzleBoardSpaceClip.name = String(i); // Added for Strict
Mode
puzzleBoardClip.addChild(puzzleBoardSpaceClip);
puzzleBoardClip.x = 400;
puzzleBoardClip.y = 325 - puzzleBoardClip.height/2; //was
200
function puzzleSolved():void{
holder.visible = false;
var tmp:Bitmap = new Bitmap(puzzleBmp);
puzzleBoardClip.addChild(tmp);
noThanks.visible = true;
playAgain.visible = true;
congrats.visible = true;
noThanks.addEventListener(MouseEvent.CLICK, clickDontPlay);
playAgain.addEventListener(MouseEvent.CLICK, clickPlay);
function clickDontPlay(evt2:MouseEvent):void
trace ("remove board clip");
removeChild(puzzleBoardClip);
// evt2.target.stop();
gotoAndPlay("child");
function clickPlay(event:MouseEvent):void
var timer:Timer = new Timer(50);
timer.start();
timer.addEventListener("timer", puzTrash);
function puzTrash(evt:Event):void{
if(threshold > 0xFFFFFF)
threshold = 0xFFFFFF;
evt.target.stop();
init();
puzzleBmp.threshold(puzzleBmp, new Rectangle(0,0,
puzzleBmp.width, puzzleBmp.height), new Point(0,0), "<=",
0xFF000000 | threshold);
threshold *= 1.2;