问StageText未调度键盘事件

EN

_input                      = new StageText(new StageTextInitOptions(true));
_input.text                 = _trackerData.trackerComment;
_input.maxChars             = Globals.TRACKER_INPUT_CHARS;
_input.fontFamily           = "Antenna Regular"; 
_input.softKeyboardType     = SoftKeyboardType.DEFAULT;
_input.returnKeyLabel       = ReturnKeyLabel.DONE;
_input.autoCorrect          = true;
_input.fontSize             = ScreenUtils.cmToPt(.25);
_input.color                = 0x000000;
_input.fontWeight           = "normal";
_input.stage                = this.stage;
_input.viewPort             = new Rectangle(    ScreenUtils.cmToPx(.35), 
                                                ScreenUtils.cmToPx(1.5), 
                                                stage.stageWidth - ScreenUtils.cmToPx(.7), 
                                                ScreenUtils.cmToPx(3)
                                            );
_input.addEventListener(KeyboardEvent.KEY_UP, keyUpEventHandler);

private function keyUpEventHandler(evt:KeyboardEvent):void
{
    trace("keyCode", evt.keyCode);
}