Android - add dialog to enable GPS

[ln-12]

I tested this library on Android. It works perfectly fine, if GPS is enabled. If not, nothing happens. The official docs state that an app should check the settings and prompt a system dialog to enable GPS. Would be nice to see this feature.

[Alex009]

yes, it will be good improvement

[ln-12]

Hey, I quickly created a pull request for the requested feature based on the code I already use in my app. Feel free to use it as a baseline for your implementation. At the moment, I have no option to run code on iOS, so I cannot provide an example for that.

[Alex009]

thx! we pull it later