So you do not want to display which apps have used how much energy since the last battery load but you want to show which apps are using the most energy in the moment? That's a bit easier. Then we do only need a way to get a list of the current running processes and their used ressources.
So you do not want to display which apps have used how much energy since the last battery load but you want to show which apps are using the most energy in the moment? That's a bit easier. Then we do only need a way to get a list of the current running processes and their used ressources.