Hello. Mobile data stays on when I’m out. And there is wifi at home. When I come home the phone connects to wifi but mobile data stays on. How to make such an app for the phone to turn off mobile data when connecting to wifi.
You do not need an app to turn off your mobile data since the settings feature for such configuration might be different to each phone manufacturer. Also, as far as I know, normally, the mobile data is automatically not being used (even though the indicator is on) while using the Wi-Fi.
This answer might be off-topic since it does not involve things related to app creating. But, I will try to help.
If you think that the data is still being used while you are using Wi-Fi. Try to disable the Wi-Fi assist feature in Settings. You may also turn off the “Mobile data always active” settings in Developer Options.
Have a nice day!