聊天框中文本随输入向上滚动

拖两个组件到舞台上TextInput（实例名为inputmc）、和TextArea（实例名为tracemc）

inputmc.addEventListener(KeyboardEvent.KEY_DOWN,inputChange);
function inputChange(e:KeyboardEvent):void
{
if (e.keyCode == 13)
{
  tracemc.appendText(inputmc.text+"\n");
  tracemc.verticalScrollBar.scrollPosition = tracemc.maxVerticalScrollPosition;
  inputmc.text = "";
}
}