Flash＆Flex SDK / AS3 - 如何保持键盘焦点？

I'm writing a flash application in Flex/AS3, and I can't seem to assign keyboard focus to it. I was mindful of this problem early on in development and added a splash screen with a "play now" button, to entice the user to click. However, the user must then click a second time on the application for the keyboard to work!I'm writing a flash application in Flex/AS3, an