You just make your app out of fragments and then use different layouts based on screen size to arrange your fragments. It's pretty straight forward and really n

You just make your app out of fragments and then use different layouts based on screen size to arrange your fragments. It's pretty straight forward and really not the problem. For general reactive design like on websites, you can just set up your layout in XML to grow correctly to fit the screen, which is something it does by default. The real problem is that Android very heavily links layout with function. In HTML-land, a designer who knows a bit of html and css can happily redesign the layout of the page. In iOS-land, a designer can use UIBuilder to redesign the layout of the page as well (they usually break it too by dragging stuff inside other stuff, but it's visual and generally fixable). In Android, redesigning the layout of an app is generally very complex and nearly always requires major code changes because of how fragments are forced to interact through the activity god object.