A single Sketch file through which you can create both Android and iOS App Icons at the same time by adding a single image of your app icon in the Artboard named App_Icon_iOS, it will reflect that image in the other Artboards and you can simply export the Artboards according to their folders. This file also includes the template for creating Launch Images for Android and iOS both at the same time by adding a single image of your launch image in the Artboard named splash_mdpi and then, you can simply export the Artboards according to their folders. But for iPhone X, you need to add background to the Artboard before exporting.
A single Sketch file through which you can create both Android and iOS App Icons at the same time by adding a single image of your app icon in the Artboard named App_Icon_iOS, it will reflect that image in the other Artboards and you can simply export the Artboards according to their folders. This file also includes the template for creating Launch Images for Android and iOS both at the same time by adding a single image of your launch image in the Artboard named splash_mdpi and then, you can simply export the Artboards according to their folders. But for iPhone X, you need to add background to the Artboard before exporting.