Restrict TextField to act like a numeric stepper - regex

Question

I am making a numeric stepper from scratch, so I want my text field to only accept numbers in this format: xx.x, x.x, x, or xx where x is a number. For example:
Acceptable numbers:
1
22
15.5
3.5
None Acceptable numbers:
213
33.15
4332
1.65
Maybe this will help some how:
http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/text/TextField.html#restrict
This is what I got so far:
var tx:TextField = new TextField();
tx.restrict="0-9."; //Maybe there is a regular expression string for this?
tx.type=TextFieldType.INPUT;
tx.border=true;
You can copy past this in flash and it should work.
Thank you very much for your help good sirs.

Answer 1

Very similar to TheDarklins answer, but a little more elegant. And actually renders _tf.restrict obsolete, but I would still recommend using it.
_tf.addEventListener(TextEvent.TEXT_INPUT, _onTextInput_validate);
Both of these event listeners here do the EXACT same function identically. One is written in a one line for those who like smaller code. The other is for those who like to see what's going on line by line.
private function _onTextInput_validate(__e:TextEvent):void
{
if ( !/^\d{1,2}(?:\.(?:\d)?)?$/.test(TextField(__e.currentTarget).text.substring(0, TextField(__e.currentTarget).selectionBeginIndex) + __e.text + TextField(__e.currentTarget).text.substring(TextField(__e.currentTarget).selectionEndIndex)) ) __e.preventDefault();
}
for a more broken down version of the event listener
private function _onTextInput_validate(__e:TextEvent):void
{
var __reg:RegExp;
var __tf:TextField;
var __text:String;
// set the textfield thats causing the event.
__tf = TextField(__e.currentTarget);
// Set the regular expression.
__reg = new RegExp("\\d{1,2}(?:\\.(?:\\d)?)?$");
// or depending on how you like to write it.
__reg = /^\d{1,2}(?:\.(?:\d)?)?$/;
// Set all text before the selection.
__text = __tf.text.substring(0, __tf.selectionBeginIndex);
// Set the text entered.
__text += __e.text;
// Set the text After the selection, since the entered text will replace any selected text that may be entered
__text += __tf.text.substring(__tf.selectionEndIndex);
// If test fails, prevent default
if ( !__reg.test(__text) )
{
__e.preventDefault();
}
}
I have had to allow xx. as a valid response otherwise you would need to type 123 then go back a space and type . for 12.3. That is JUST NOT NICE. So 12. is now technically valid.

Answer 2

package
{
import flash.display.Sprite;
import flash.text.TextField;
import flash.text.TextFieldType;
import flash.events.TextEvent;
public class DecimalPlaces extends Sprite
{
public function DecimalPlaces()
{
var tf:TextField = new TextField();
tf.type = TextFieldType.INPUT;
tf.border = true;
tf.width = 200;
tf.height = 16;
tf.x = tf.y = 20;
tf.restrict = ".0-9"
tf.addEventListener(TextEvent.TEXT_INPUT, restrictDecimalPlaces);
addChild(tf);
}
function restrictDecimalPlaces(evt:TextEvent):void
{
var matches:Array = evt.currentTarget.text.match(/\./g);
var allowedDecimalPlaces:uint = 1;
if ((evt.text == "." && matches.length >= 1) ||
(matches.length == 1 && (evt.currentTarget.text.lastIndexOf(".") + allowedDecimalPlaces < evt.currentTarget.text.length)))
evt.preventDefault();
}
}
}