这个问题在这里有回答
http://stackoverflow.com/questions/22190578/adt-will-not-allow-creation-of-android-activity?answertab=votes#tab-top
粘贴过来
Okay, this worked for me: "Help" -> "Install new software" and install (this will update it) from this url: https://dl-ssl.google.com/android/eclipse/ I guess the Android website doesn't have an up-to-date version of ADT? Not sure where you're supposed to download the latest version from. – NewShelbyWoo Mar 6 at 5:57
也就是说 需要更新ADT才行。。。。
利用eclipse的help->install new software 然后加上这个网址https://dl-ssl.google.com/android/eclipse/
下载完安装好提示重启软件就好了
最开始的答案是在这里的
https://code.google.com/p/android/issues/detail?id=66647
5楼