android acitivity没有在androidmanifest.xml中注册

I came across a problem in a job interview that whether I can dynamically add a new activity to an Android application without releasing a new version of the app. And he told me that there exists certain mechanism that we could dynamically change the Activity to a new one, without registering in the AndroidManifest.xml file. I searched some documents, but did not found possible way to do this. I came across a problem in a job interview that