Android布局设计：layout.xml与dimens.xml

Question

I am a newbie android developer. Recently I am reading Google's specification of providing alternative resources to support different screen size.

https://developer.android.com/training/multiscreen/screensizes.html

I know we can provide resource directories with specific qualifiers to achieve this,

eg layout-sw320dp/layout.xml , layout-sw480dp/layout.xml , layout-sw600dp/layout.xml .

Meanwhile, I also found some developers who create various dimens.xml in the values folders with different screen size qualifiers,

eg values-sw320dp/dimens.xml , values-sw480dp/dimens.xml , values-sw600dp/dimens.xml .

I am wondering which approach would be better for maintaining the layout. My intuition told me if I have controlled the screen size rendering by different layout.xml . Then I do not need to use dimens.xml to fit different screen size. Is it a right thought?

Answer 1

You should use dimens.xml if the only thing changing is the size. You should use layout.xml if you're changing the actual views.

Why? Because of maintenance. If in 3 months you decide you want to change the background color of a view and you have 4 layout files, you need to go and change it in 4 places. Eventually you'll forget one. If you used dimens properly, you only need to change it in 1 place.

Prefer to use dimens wherever possible.