Problems with a simple physics system in AS3 - actionscript-3

Question

Well, first of all, I'm a student, so I really beg to you to be patient in the answer. I'm not a english speaker too, by the way.
Everything begins because I'll attend a Game Jam and I already started to write (or trying to write) a simple "physics" code, who I really was thinking would be easy.
I was working with classes and using hitTestObject for colision detection.
Actually I was having issues since the begin, but I was constantly trying to fix it. At this time the code really sucks and I'm already thinking in another way to do it. But something puzzles me.
Here's a part of the the code who I'd already written (It probably seems very newbie). Most part of the code is bullshit, just take a look in the last "else if".
Note: this is the "block" class, and the "obj" it's the Movie Clip of the player.
public function checkObj(obj:MovieClip):void
{
if (this.hitTestObject (obj))
{
if (this.y < obj.y)
{
if (this.x - this.width/2 <= obj.x+obj.width/2 && this.x + this.width/2 >= obj.x-obj.width/2)
{
downCol = true;
}
}
else if (this.y + this.height/2 > obj.y-obj.height/2)
{
if (this.x - this.width/2+2 <= obj.x+obj.width/2 && this.x + this.width/2-2 >= obj.x-obj.width/2)
{
upCol = true;
onBox = true;
}
}
if (this.x - this.width/2 >= obj.x+obj.width/2-2)
{
if (this.y - this.height/2<= obj.y+obj.height/2&& this.y + this.height/2>= obj.y-obj.height/2)
{
leftCol = true;
}
}
else if (this.x + this.width/2 <= obj.x-obj.width/2-2)
{
if (this.y + 5>= obj.y-obj.height/2 && this.y - 5<= obj.y+obj.height/2)
{
trace ("Collided on right");
rightCol = true;
}
}
}
}
For some reason, this way it doesn't work. It never returns me the message.
But if I do a little change:
public function checkObj(obj:MovieClip):void
{
if (this.x + this.width/2 <= obj.x-obj.width/2-2)
{
objOnRight = true;
}
if (this.hitTestObject (obj))
{
//...
else if (objOnRight == true)
{
if (this.y + 5>= obj.y-obj.height/2 && this.y - 5<= obj.y+obj.height/2)
{
rightCol = true;
trace ("Collided on right");
}
}
}
}
It works. Just because I checked the X axis of "obj " before testing the collision. I know this code it's bad at all, but if someone could help me to understand that error and maybe guide me to a more efficient solution I'll really appreciate it! Thank you.

Answer 1

Try this for the last else if
else if (this.x + this.width / 2 <= obj.x + obj.width / 2 - 2) {
if (this.y + 5 >= obj.y - obj.height / 2 && this.y - 5 <= obj.y + obj.height / 2) {
trace("Collided on right");
rightCol = true;
}
}
just change the "-" to "+" .

Answer 2

Ok, forget it. I wrote a brand new code, without hitTest, and it works like a charm. I think the Math.abs solved the problem with negative numbers.
Thanks for your help, kare81.
Here's the code:
public function checkObj(obj:MovieClip,place:int):void
{
if (obj.x + obj.width / 2 > this.x - width / 2 && obj.x < this.x - width / 2 + 7 && Math.abs (obj.y - y) < height / 2)
{
obj.x = this.x - width / 2 - obj.width / 2;
}
if (obj.x - obj.width / 2 < this.x +width / 2 && obj.x > this.x + width / 2 - 7 && Math.abs (obj.y - y) < height / 2)
{
obj.x = this.x +width / 2 + obj.width / 2;
}
if (Math.abs (obj.x- this.x) < width / 2 + obj.width / 2 && obj.y<y-height/2 && obj.onFloor > y-height/2 && obj.onBlock != place)
{
obj.onFloor = y - height / 2;
obj.onBlock = place;
}
if (Math.abs (obj.x - this.x) >= width / 2 + obj.width / 2 && obj.onBlock == place)
{
obj.onFloor = 450;
}
if (obj.y - obj.height / 2 < y + height /2 && obj.y > y && Math.abs (obj.x - this.x) < width / 2 + obj.width / 2)
{
obj.y = y + height / 2 + obj.height / 2;
}
}