Load value from dimens.xml and make it negative

Question

In an xml document, is there any way to load a value from dimens.xml and make it negative? For example, if I have:

<dimen name="x">20dp</dimen>

Is it possible to do something like this:

android:layout_marginRight="-@dimen/x"

So I in de facto get:

android:layout_marginRight="-20dp"

Answer 1

That is not possible in standard layout XML. You could retrieve the dimension value in Java, multiply it by -1, and apply it in Java.

You could even do that in the form of a custom attribute (e.g., yourapp:layout_negativeMarginRight) in your own custom subclass of ViewGroup, if you really wanted. This would seem to be overkill.

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UPDATE: This is now somewhat possible via data binding expressions:

android:padding="@{0.75f * @dimen/icon}"

It does not work for margins or any other layout attributes due to the lack of binding adapters which you can implement. See this bug.