ActionScript 3 - Walls don't collide properly - actionscript-3

Question

For several weeks I'm been trying to make my topdown game. It went well for some time, but then at some point I wanted to create a scrolling map with walls everywhere. Now, to make it easy to create the map (and add more later) I made a class called "Wall" which I will hit test. This works, when it hits, the map must stop scrolling. It does, so good so far.
Now, when the player moves away from the object, I want the map to be able to scroll again, this works too, but now the player can't move to the side the player came from. I know this is because I need to define the sides, where the player enters, in order tell the game which movement must be set to zero at that point.
You can see the code here:
public function AddWalls(player:MovieClip)
{
WallObjects = new Array();
for (var i:int = 0; i < this.numChildren; i++)
{
var mc = this.getChildAt(i);
if (mc is Wall)
{
var wallobj:Object = new Object();
wallobj.mc = mc;
wallobj.leftside = mc.x;
wallobj.rightside = mc.x + mc.width;
wallobj.topside = mc.y;
wallobj.bottomside = mc.y + mc.height;
wallobj.width = mc.width;
wallobj.height = mc.height;
WallObjects.push(wallobj);
}
}
}
public function EnableCollisionWithWalls():void
{
for (var k:int = 0; k < WallObjects.length; k++)
{
//if (player.y > WallObjects[k].topside && player.y < WallObjects[k].bottomside && player.x > WallObjects[k].leftside && player.x < WallObjects[k].rightside)
if (player.hitTestObject(WallObjects[k].mc))
{
if (player.x > WallObjects[k].leftside && player.x < WallObjects[k].leftside+15)
{
Lefthit = true;
trace(DebugVar);
DebugVar++;
player.x = WallObjects[k].leftside;
Scroll_x = 0;
}
else
if ( player.x < WallObjects[k].leftside -1 || (player.y > WallObjects[k].leftside ))
{
Lefthit = false;
}
if (player.hitTestObject(derp))
{
Lefthit = false;
}
}
}
}
public function EnableMovement():void
{
map.x += Scroll_x;
map.y += Scroll_y;
for (var i:int = 0; i < this.numChildren; i++)
{
var mc = this.getChildAt(i);
if (mc is Wall)
{
mc.x += Scroll_x;
mc.y += Scroll_y;
}
}
}
public function MovementKeysDown(move:KeyboardEvent):void
{
var Speed:int = -5;
switch (move.keyCode)
{
case 37: // venstre knap
Scroll_x = -Speed;
break;
case 38: // op
Scroll_y = -Speed;
break;
case 39: // højre knap
Scroll_x = Speed;
if (Lefthit)
{
Scroll_x = 0;
}
break;
case 40: // ned
Scroll_y = Speed;
break;
default:
}
}
public function MovementKeysUp(move:KeyboardEvent):void
{
switch (move.keyCode)
{
case 37:
Scroll_x = 0;
break;
case 38:
Scroll_y = 0;
break;
case 39:
Scroll_x = 0;
break;
case 40:
Scroll_y = 0;
break;
default:
}
}
Might be some syntax errors (since I removed some code in this editor).
You can see the current version here.
In this version the scroll keeps on going. I did come up with a "fix" for it, by check if the player was 1 pixel away from the movieclip, inside the hit test (which for some reason works, which I guess it shouldn't since it doesn't hit anymore) and then setting the Lefthit to false. However this is not a good solution and if you continue up or down away from the movieclip, you are still not able to go right anymore...
I've been baffled by this for a long time, so I thought it was about time I asked for help. I couldn't find anything on how to control movement in a top-down game, with a scrolling map + wall :/

Answer 1

The simplest (but not most resource friendly) solution (if you anyway have a single storage for walls) is iterating through the walls and instead of using the Flash default hitTest (I don't like the way it works since ActionScript 2) - just check the coordinates and if you see that there's going to be a collision on the next simulation step - handle it according to the game logic.
The most useful optimization for this algorithm is creating a filter/data structure for getting only walls that are near to the player and so can be affected to the test for collisions.