Storing dimensions in xml file in Android

I am trying to consistently use the same dimension in all the views in my android app (e.g., a left margin of 20dp). If I were using HTML, I would simply use a CSS file, but I am at a loss of how to do this on Android.

Is there a way I can store this value in a xml file inside res/values and then use it in layouts?

e.g., I thought of storing them in strings.xml like

<string name="app_wide_left_padding">20dp</string>

and then using the following text in layout.xml

android:paddingLeft="@string/app_wide_left_padding"

but I am not sure it will work. Am I on the right track?

Thanks in advance for your answers.