Perhaps you are resizing the height of your TextField somewhere else in your code then? Because the auto-sizing of the font definitely works. Try doubling the height of your TextField upon creation.
Also, the margins on an Android TextField is much much larger than it is on iOS. This can't be changed programmatically natively. That's just how Google's made the UI theme. If your TextField height is shorter than normal (ie: shorter than what you are seeing in other Android apps), then that's a problem too. Your TextField will need to be taller.
And again, the ***best*** solution is to size the height of the field based on the default system font size. This will work on all platforms and display resolutions/DPIs. How you're trying to size it now is not full proof.