Action Script 3. Platform game physics glitch (gravity) - actionscript-3

Question

when my player touches the floor, he is unable to move because he is on the floor and being incremented up.
In the main class I have the movement
private function processMovement():void
{
if (touchingGround)
{
if (upKey)
{
character.jumpUp();
}
if (leftKey)
{
character.moveLeft();
}
if (rightKey)
{
character.moveRight();
}
if (!leftKey && !rightKey && !upKey)
{
character.dontMove();
}
}
}
Then in the character class you will see this.
public class player extends OnGround
{
public var canJumpAn:Boolean;
public var attackAn:Boolean;
public var jumpheight:Number = 18;
public function player()
{
addEventListener(Event.ADDED_TO_STAGE, onAdd);
}
private function onAdd(e: Event): void
{
removeEventListener(Event.ADDED_TO_STAGE, onAdd);
}
public function moveLeft():void
{
//decrease VELOCITY
xV -= 2;
if (xV > -7)
{
xV = -7;
}
this.gotoAndStop("run");
//add this to the Mc . x pos baby.
this.x += xV;
this.scaleX = -1;
charIsrunning = true;
}
public function moveRight():void
{
//increase VELOCITY
xV += 2;
if (xV > 7)
{
xV = 7;
}
this.gotoAndStop("run");
//add this to the Mc . x pos baby.
this.x += xV;
this.scaleX = 1;
charIsrunning = true;
}
public function dontMove():void
{
//if no button presses then do this
this.gotoAndStop("stop");
//slowd down ball
xV *= friction;
charIsrunning = false;
isDefending = false;
//stop the ball if you're not moving
if (xV > - 1 && xV < 1)
{
xV = 0;
}
}
override public function positionOnLand():void
{
isJumping = false;
///=gotoAndStop(1);
}
public function defend():void
{
isDefending = true;
this.gotoAndStop("defend");
charIsrunning = false;
}
public function attack():void
{
this.gotoAndStop("attack");
}
public function jumpUp():void
{
if (!isJumping)
{
isJumping = true;
this.gotoAndStop("jump");
//
}
}
}
}
OnGround is another class that player extends, as you can see.
public class OnGround extends MovieClip
{
public var grav:Number;
public var friction:Number;
public var xV:Number;
public var yV:Number;
protected var charIsrunning:Boolean;
protected var isDefending:Boolean;
protected var isJumping:Boolean;
public function OnGround()
{
addEventListener(Event.ADDED_TO_STAGE, init)
charIsrunning = false;
isDefending = false;
//gotoAndStsop("jump");
}
private function init(e:Event):void
{
removeEventListener(Event.ADDED_TO_STAGE, init);
//gravity
grav = 0.6;
//y velocity
yV = 0;
//x velocity
xV = 0;
//
friction = 0.9;
addEventListener(Event.ENTER_FRAME, fall);
}
private function fall(e:Event):void
{
//add grav to y VELOCITY
yV += grav;
trace(yV);
this.y += yV
}
public function incrementUp():void
{
this.y -= 0.1;
//trace("incrementing");
}
public function keepOnGround():void
{
//trace("onGroundBitch");
grav = 0;
yV = 0;
positionOnLand();
}
public function positionOnLand():void
{
//overide
}
}
}
This is a function that's in the main class
for (var c:int = 0; c < childrenOnStage; c++)
{
if (getChildAt(c).name == "player")
{
if (ground.level1Ground.hitTestPoint(getChildAt(c).x + 13, getChildAt(c).y, true) || ground.level1Ground.hitTestPoint(getChildAt(c).x - 13, getChildAt(c).y, true))
{
getChildAt(c).y --;
//OnGround(getChildAt(c)).incrementUp();
OnGround(getChildAt(c)).keepOnGround();
touchingGround = true;
}
else
{
touchingGround = false;
}
The problem is that when the player touches the ground then it's y position is incremented until it isn't touching the ground and then it's suppose to be kept on the ground by turning grav to = 0 and y velocity to 0.
This means gravity is turned off and the players y position will not shift up (when I jump)
or when go down to be kept on ground.
I would appreciate it if someone can lend me a hand or point me in the correct direction.

Answer 1

I'm not sure why you'd have a gravity value per object unless you really intend to have different object instances have individual gravities.
If not I'd reference a gravity constant instead.
Is anti-gravity a feature of the game? if not then I'd avoid setting gravity to 0. It may 'work' (to an extent) but it's not a good model/abstraction of reality.
Rather, what I would do is seperate the force applied and the current momentum:
The (downward) force of gravity is applied at all times.
When you're standing on the ground an upward force equal and opposite to gravity is applied.
When you jump, add a one-off instance of upward force.
Use the current forces to change the current momentum and use the current momentum to change the position.