When to use attrs.xml, when dimens.xml?

Question

I like to integrate ads with AppLovin into my Android App.

In their documentation they say:

Declare the base banner height of 50dp in res/values/attrs.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <dimen name="banner_height">50dp</dimen>
</resources>

I also have a dimens.xml present with other <dimen... value's for my app. They work from there as well.

What is the difference between attrs.xml and dimens.xml? What to use in a situation like this?

Answer 1

attrs.xml is a file that allows you to define custom attributes for your views in XML layout files. These attributes can be used to customize the appearance and behavior of your views, and can be accessed programmatically in your Java code.

dimens.xml on the other hand, is a file that allows you to define dimension values for use in your app. These values can be used to set the size and layout of views in your XML layout files, and can also be accessed programmatically in your Java code.

In this situation, you should use dimens.xml to define the banner_height dimension, because you will use this value to set the height of the banner ad view in your layout.

You could also use attrs.xml to define the banner_height attribute, but since you are defining a dimension value, not an attribute, it would be better to use dimens.xml instead.

Answer 2

It doesn't actually matter - <attr> and <dimen> are both value resources, and you can put them in any file in the res/values folder. They'll all be combined into the same set of resources, so the actual file you use is up to you! So you can do this if you want:

# res/values/whatever.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <dimen name="someDimension">48dp</dimen>
    <attr name="someColour" format="color"></attr>
</resources>

and it'll work exactly the same as if you used attrs.xml and dimens.xml. It's just convention to put attrs and declare-styleable things in a file called attrs.xml, all your dimension resources in dimens.xml, all your strings in strings.xml...

But you don't have to do that, it's up to you! For example, you might want certain resource strings to be stored in a different file, for organisation (maybe they shouldn't be translated). Or maybe some values are common to all configs and you want those in a single file, and you want a separate file for the qualified stuff (that goes in folders based on API level, night theme etc)