AS3 Character jumping/falling problems - actionscript-3

Question

I am having problems with getting the character to jump/fail when the up arrow is pressed. I'm trying to make it so when the up arrow key is pressed once it will jump a certain height then fall.
Here is my movement code:
public var gravity:int = 2;
public function fireboyMovement(e:KeyboardEvent):void
{
if (e.keyCode == 37) //right
{
fireboy1.x = fireboy1.x -5;
checkBorder()
}
else if (e.keyCode == 39) //left
{
fireboy1.x = fireboy1.x +5;
checkBorder()
}
if (e.keyCode == 38) //up
{
fireboy1.y = fireboy1.y -20;
fireboy1.y += gravity;
checkBorder()
}

Answer 1

Your issue is you need to increment the players position over time (and not all at once).
You can either use a tweening engine (like tweenlite), or roll your own timer or enter frame handler.
Here is an example of the latter:
if (e.keyCode == 38) //up
{
if(!isJumping){
isJumping = true;
velocity = 50; //how much to move every increment, reset every jump to default value
direction = -1; //start by going upwards
this.addEventListener(Event.ENTER_FRAME,jumpLoop);
}
}
var isJumping:Boolean = false;
var friction:Number = .85; //how fast to slow down / speed up - the lower the number the quicker (must be less than 1, and more than 0 to work properly)
var velocity:Number;
var direction:int = -1;
function jumpLoop(){ //this is running every frame while jumping
fireboy1.y += velocity * direction; //take the current velocity, and apply it in the current direction
if(direction < 0){
velocity *= friction; //reduce velocity as player ascends
}else{
velocity *= 1 + (1 - friction); //increase velocity now that player is falling
}
if(velocity < 1) direction = 1; //if player is moving less than 1 pixel now, change direction
if(fireboy1.y > stage.stageHeight - fireboy1.height){ //stage.stageheight being wherever your floor is
fireboy1.y = stage.stageHeight - fireboy1.height; //put player on the floor exactly
//jump is over, stop the jumpLoop
this.removeEventListener(Event.ENTER_FRAME,jumpLoop);
isJumping = false;
}
}