TraceView file has no data

Question

I have added Debug.startMethodTracing("can_act"); in onCreate and Debug.stopMethodTracing(); in onDestroy.The trace file is of size 0KB.

What went wrong?

EDIT:

It writes out a trace file but it is of size 0 KB.I use the methods in a custom Camera activity on a device.I am calling it after super.onDestroy();