How can I debug the engine code in my android project

I toggled several breakpoints both in engine and my own code, run this app on my android phone, only the breakpoints in my code were valid and hit, others in engine code were invalid.
Could anybody help me please?
Thanks a lot!

What method did you use for debugging your code on Android? What version of UE4 are you using? Is it an official build, or a source build?