which method should i use to create a new keyboard using adobe flash - actionscript-3

Question

I'm trying to create a new keyboard somehow, for educational purposes.
I've written this code using actionscript 3.I've created an input text field (named it t1) .when the user presses q button on keyboard(which has an ASCII aquals 81 ) I want the letter b to be printed out on the text field so i've written this code :
stage.addEventListener(KeyboardEvent.KEY_DOWN, pressing);
function pressing(event:KeyboardEvent):void
{
//trace(event.keyCode);
if(event.keyCode==81)
t1.replaceSelectedText("b");
}
the problem was that the method replaceSelectedText prints the tow letters on the screen(q&b) which method can i use instead?
Any help would be appreciated.

Answer 1

When using the replaceSelectedText method, you first need to select the text you want to replace. This can be done with the "setSelection" method. This from the adobe help website:
setSelection(beginIndex:int, endIndex:int):void
"Sets as selected the text designated by the index values of the first and last characters, which are specified with the beginIndex and endIndex parameters."
At the moment, since you don't have any text selected, it appears to just be adding the text "b" as it's replacing nothing. Therefore, you should try first selecting the "q".
Alternatively, you can just use a different method. from the adobe help website:
replaceText(beginIndex:int, endIndex:int, newText:String):void
"Replaces the range of characters that the beginIndex and endIndex parameters specify with the contents of the newText parameter."
This would cut out an extra line of code.
I haven't actually done this myself, so if that doesn't work, here's the link to the adobe help page for Text Fields: http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/text/TextField.html

Answer 2

I think that to do what you are looking for ( replace a char when it's typed ), a KeyboardEvent.KEY_DOWN is not enough, because when that event is fired, the text is not yet changed, so any change that you did in its handler to your text field will not cancel the insertion of the current typed char. Also, using KeyboardEvent.KEY_UP ( in addition to KeyboardEvent.KEY_DOWN ) will not resolve the problem, because you can fire n times a KeyboardEvent.KEY_DOWN event with the KeyboardEvent.KEY_UP event fired once !
So, I think that the best event that can do the job is the Event.CHANGE event which is fired every time the text of your text field is changed, so you can do like this :
// is there a char to replace ?
var replace_char:Boolean = false;
// the position of the char that we want to replace
var char_position:int = -1;
var text_input:TextField = new TextField();
text_input.type = 'input';
text_input.border = true;
text_input.addEventListener(Event.CHANGE, onTextChange);
function onTextChange(e:Event):void {
if(replace_char && char_position >= 0){
text_input.replaceText(char_position, char_position + 1, 'b');
replace_char = false;
}
}
addChild(text_input);
stage.addEventListener(KeyboardEvent.KEY_DOWN, _onKeyDown);
function _onKeyDown(e:KeyboardEvent):void {
if(e.keyCode == 81) {
replace_char = true;
char_position = text_input.selectionBeginIndex;
}
}
EDIT :
To use a list of keys and their equivalents, you can use an object to stock your keys like this :
// list of all keys (chars) and their equivalents
var chars:Object = {
81: 'b', // q => b
83: 'v', // s => v
68: 'c' // d => c
// other chars
}
var char_to_replace:int = -1;
// other instructions
function onTextChange(e:Event):void {
if(replace_char && char_position >= 0 && char_to_replace >= 0){
// get the equivalent of the pressed key from chars object using : chars[key_pressed]
text_input.replaceText(char_position, char_position + 1, chars[char_to_replace]);
replace_char = false;
}
}
// other instructions
function _onKeyDown(e:KeyboardEvent):void {
if(chars[e.keyCode]) {
replace_char = true;
// save the last pressed key to get its equivalent, or save this last one directly, to replace it next
char_to_replace = e.keyCode;
char_position = text_input.selectionBeginIndex;
}
}
Hope that can help.