restricting movement from arrow keypad

[garrybibson]

Hi,

I am playing around making a little game from a tutorial and i am having trouble trying to limit where the "car" can travel on the screen. At present it has a free range and will disappear out of view if asked to. Can anyone make a suggestion what code i need to add? I have been searching and trying for two hours but just cant get it to work.

This is what i have at present

code:

---

listener = new Object();

listener.onKeyDown = function () {

	delete car.onEnterFrame;

	var yval = 0; 

	var xval = 0; 

	switch (Key.getCode()) {

	  case Key.DOWN: yval = 8; 	car.rotate(30,30); break;

	  case Key.UP: yval = -8; 	car.rotate(-30,30); break;

	  case Key.LEFT: xval = -8; car.rotate(-30,30);break;

	  case Key.RIGHT: xval = 8; car.rotate(30,30);

	}

	car.onEnterFrame = function(){

		this._y += yval; 

		this._x += xval;



	}

};

---

Basically i just want to limit the cars movement to within the track!
Any help or advice would be greatly welcomed.

Barry

EDIT: Added as tags. - jbum

[jbum]

Here are two methods you can use:

Method #1: You can add bounds to your onEnterFrame handler, as follows:

code:

---

// Adjust these numbers to taste

minX = 10;

maxX = Stage.width-10;

minY = 10;

maxY = Stage.height-10;



car.onEnterFrame = function() 

{

  this._y = Math.min(Math.max(minY, this._y + yval), maxY);

  this._x = Math.min(Math.max(minX, this._x + xval), maxX);

}

---

This will keep the car within a rectangle specified by minX-maxX and minY-maxY.


Method #2: If you want to restrict the car to a more complicated shape, then you'll probably want to do a hitTest on the track, like so:

For example:

code:

---

car.onEnterFrame = function() 

{

  var nx = this._x + yval;

  var ny = this._y + xval;

  if (_root.track.hitTest(nx,ny,true))

  {

     this._x = nx;

     this._y = ny;

  }

}

---

[garrybibson]

i want a rectangle shape so the first bit of code is fine.

Thank you very much, people like you are priceless!

Barry