GPS Joystick (No Root Needed Only Marshmallow)

[rling]

I have tried Fly GPS, but sometimes it will back to current position immediately .... how to solve this situation?

Need to disable "fused location" services in your system. This is a system service that polls and merge all your GPS data, from wi-fi, cellular data, and built in GPS. With fused location servcies active, this polling can sometimes select your wi-fi as location of choice, and so, you teleport before the gps spoofer (which fools your built in GPS) takes over.

You can also increase the rate the gps spoofer updates the system to prevent the wi-fi data being taken as priority.

[rling]

is fly gps safe?

All of these apps are against ToS for PoGo and can all end up getting your account banned. That said, Fly GPS and other GPS spoofers, all change the GPS data the game receives from your phone. It send the fake GPS coordinates but does not send any height data. It is believed that PoGo does not record height, nor your GPS tracking data, ie no data to enable replay of where or how you travelled. If both latter assumptions are correct, then technically, the GPS spoofing is not detected and so, a ban is less likely. If the assumption is wrong, then one can expect to be banned for using it.