Where are the layout files? / Why doesn’t Flutter have layout files?
In the Android framework, we separate an activity into layout and code. Because of this, we need to get references to views to work on them in Java. (Of course Kotlin lets you avoid that.) The layout file itself would be written in XML and consist of Views and ViewGroups.
Flutter uses a completely new approach where instead of Views, you use widgets. A View in Android was mostly an element of the layout, but in Flutter, a Widget is pretty much everything. Everything from a button to a layout structure is a widget. The advantage here is in customisability. Imagine a button in Android. It has attributes like text which lets you add text to the button. But a button in Flutter does not take a title as a string, but another widget. Meaning inside a button you can have text, an image, an icon and pretty much anything you can imagine without breaking layout constraints. This also lets you make customised widgets pretty easily whereas in Android making customised views is a rather difficult thing to do.
Isn’t drag-and-drop easier than making a layout in code?
In some respect, that is true. But a lot of us in the Flutter community prefer the code way but that does not mean drag-and-drop is impossible to implement. If you completely prefer drag-and-drop, then Flutter Studio is a fantastic resource I’d recommend which helps you generate layouts from drag-and-drop. It’s a tool I’m genuinely impressed by and would love to see how it grows.