BitmapData Collision - actionscript-3

Question

I have been trying to use BitmapData for collision detection, but have failed so far, and I don't know why. The code compiles, but doesn't do anything (when it should print "hit" ). Can anyone help me?
package
{
import flash.events.KeyboardEvent;
import flash.events.Event;
import flash.display.MovieClip;
import flash.ui.Keyboard;
import flash.display.BitmapData;
import flash.geom.Point;
public class Main extends MovieClip
{
private var spd:int = 5;
private var pressedKeys:Object = {};
private var bgMask:BitmapData;
private var plMask:BitmapData;
private var wall:Wall = new Wall();
public function Main()
{
var bgBitMapData:BitmapData = new BitmapData(bg.width,bg.height,true,0);
bgMask = bgBitMapData.clone();
wall.x = bg.x;
wall.y = bg.y;
bgMask.draw( wall );
var plBitMapData:BitmapData = new BitmapData(pl.width,bg.height,true,0);
plMask = bgBitMapData.clone();
bgMask.draw( pl );
stage.addEventListener(KeyboardEvent.KEY_DOWN,this.keyPressHandler);
stage.addEventListener(KeyboardEvent.KEY_UP,this.keyPressHandler);
stage.addEventListener(Event.ENTER_FRAME,this.gameLoop);
}
public function keyPressHandler( evt:KeyboardEvent ):void
{
if (evt.type == KeyboardEvent.KEY_DOWN)
{
pressedKeys[evt.keyCode] = 1;
}
else
{
delete pressedKeys[ evt.keyCode ];
}
}
public function inputHandler():void
{
var moveXBy:int;
var moveYBy:int;
if (pressedKeys[Keyboard.J])
{
moveXBy -= spd;
}
if (pressedKeys[Keyboard.K])
{
moveYBy += spd;
}
if (pressedKeys[Keyboard.L])
{
moveXBy += spd;
}
if (pressedKeys[Keyboard.I])
{
moveYBy -= spd;
}
pl.x += moveXBy;
pl.y += moveYBy;
}
public function playerWallCollision():void
{
if ( plMask.hitTest( new Point( wall.x, wall.y ), 1, bgMask, new Point( pl.x, pl.y ), 1))
{
trace( "hit" );
}
}
public function gameLoop( evt:Event ):void
{
wallUpdate();
inputHandler();
playerWallCollision();
}
private function wallUpdate()
{
wall.x = bg.x;
wall.y = bg.y;
}
}
}

Answer 1

as far as this script tells me, after the lines:
var bgBitMapData:BitmapData = new BitmapData(bg.width,bg.height,true,0);
// bgBitMapData is an empty BMP at this point cause its just freshly instanciated
bgMask = bgBitMapData.clone();
wall.x = bg.x;
wall.y = bg.y;
bgMask.draw( wall );
var plBitMapData:BitmapData = new BitmapData(pl.width,bg.height,true,0);
// no idea y you make this plBitMapData anyway
plMask = bgBitMapData.clone();
// now you clone the empty bgBitMapData to be plMask
bgMask.draw( pl );
plMask is never filled with anything! So compared with an empty BitmapData should allways return false.
So the answer to when should it output hit - never ;)
And as a sidenote try to keep it more readable by 1. write a comment every here and there what your intention is and 2. go for direct ways :
var bgBitMapData:BitmapData = new BitmapData(bg.width,bg.height,true,0);
bgMask = bgBitMapData.clone();
// this position seems just wrong to me wall.x or wall.y do not effect the draw so keep it somewhere else... since you will copy the inside of wall
wall.x = bg.x;
wall.y = bg.y;
bgMask.draw( wall );
For me it should look like:
// placing a wall to new / init coordinates
wall.x = bg.x;
wall.y = bg.y;
// drawing wall on bgMask for hittesting against player or what ever you intende here
bgMask = new BitmapData(bg.width,bg.height,true,0);
bgMask.draw( wall );