Why doesn't stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyDown, true) work? - actionscript-3

Question

I want to listen to stage for keyboard event, and I want to catch an event directly when it appears (not in bubbling or target). Why can't I do this?
Actually it seems that I can't use useCapture for keyboard events at all.
I want to open my inner console window by pressing tilda button, and change focus to input field. So, I wrote something like this
public function init(stage:Stage):void
{
stage.addEventListener(KeyboardEvent.KEY_DOWN, onStageKeyDown);
}
private function onStageKeyDown(event:KeyboardEvent):void
{
event.stopImmediatePropagation();
switch(event.keyCode)
{
case Keyboard.BACKQUOTE:
visible = !visible;
stage.focus = visible ? inputField : stage;
break;
}
}
The problem is, it writes "`" character in my input, which I don't want it to do. So, I decided to try to listen to keyboard event in capture phase to stop its propagation. But it seems that stage can't have capture phase, because there is no nodes before it. How can I handle that situation properly?

Answer 1

To simply answer your question, you can listen for keyboard events on the capture phase.
Most likely, the reason you can't, is because nothing has focus. If nothing has focus in your application then the stage will not get a keyboard event. By default, when a swf runs nothing has focus.
Give an item focus when your application starts (anything besides the stage itself), and the event will come.
public function init(stage:Stage):void
{
stage.focus = this; //assuming this is the document class
stage.addEventListener(KeyboardEvent.KEY_DOWN, onStageKeyDown, true);
}
Now, to follow up with what you are actually trying to accomplish (aside from your actual question) all you need to do is listen for the right event (TEXT_INPUT). Your answer is close, but it can be much simpler without the need for flags or a key down listener:
stage.focus = this; //give something focus, probably not needed if you have to click the text input in order to input text
//listen on the capture phase for text input
stage.addEventListener(TextEvent.TEXT_INPUT, onStageTextInput, true);
function onStageTextInput(event:TextEvent):void
{
switch(event.text)
{
//if the new text was a backquote or # sign, don't let the event trigger it's normal action
case "`":
case "#":
event.preventDefault(); //prevent default is needed
break;
}
}

Answer 2

I finally found a workaround for this problem.
First of all: handling and stopping KeyboardEvent.KEY_DOWN is NOT preventing TextField from getting input. That's sad because in this case it would be useful, but it seems there is some other reasons for not doing this.
So, what I should do is listen for TextEvent.TEXT_INPUT by inputField
inputField.addEventListener(TextEvent.TEXT_INPUT, onTextInput);
and listen to KeyboardEvent.KEY_DOWN by stage
stage.addEventListener(KeyboardEvent.KEY_DOWN, onStageKeyDown);
in case I may still want to put tilda of backquote signs in my TextField (for example by coping and pasting them) I decided to use a flag
private function onStageKeyDown(event:KeyboardEvent):void
{
switch(event.keyCode)
{
case Keyboard.BACKQUOTE:
...
inAction = true;
break;
}
}
so when TextEvent.TEXT_INPUTevent fires I can see if that was opening window action or not. And if it is, then preventDefault() behaviour, which means NOT inputting received sign in TextField
private function onTextInput(event:TextEvent):void
{
if(inAction)
{
event.preventDefault();
inAction = false;
}
}