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kotlinlang

Designer of my project uses new iPhone dimensions for screen mocks, like 19:9.

Yet most of older Android phones which users will use still have 16:9 and bottom content usually has to be put into a scrollview not to be cut off.
It doesn’t seem like a great choice, what am I supposed to do?

Do I change margins based on screen height, force everything smaller, or something else?

Use Percentages. Constraint Layout is your friend.

I am not saying totally give up on margins, I still use it.
But let's say anything more than 48dp of margin can be replaced by guidelines and using percentages.

That helps a lot and doesn't matter for the mock sizes.

this certainly helps, doesn’t solve all of my problems though

What else remains? Even for Images, you can use percentages and dimension ratio, so that should be fine too. Especially if you are using SVGs/Vectors.

sometimes I just have a screen fully loaded with views which doesn’t have much margin space, but I guess this is fine when scrollable

In ScrollView you will have to use margins regardless, since you can't really form chains in it. But yeah I think you can judge it by seeing the specs and adjust accordingly.