Custom attrs parameter used in styles.xml

Question

I have a set of custom Android layout parameters defined in attrs.xml. Now I would like to use some tags in my styles.xml file.

At the moment I get this error:

error: Error: No resource found that matches the given name: attr 'custom:tag'

I have tried declaring custom XML namespace as follows:

<resources
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:custom="http://schemas.android.com/apk/res/com.my.project"
>

hoping, that the same logic used in every layout declaration can be applied here, but with no success.

Answer 1

The XML namespace mechanism is used to namespace tags and attributes. When you define a style like this:

<?xml version="1.0" encoding="utf-8"?>
<resources
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:custom="http://schemas.android.com/apk/res/com.my.project">

    <style name="my_style"> <item name="custom:tag">some_value</item> </style>

</resources>

you are trying to apply XML namespacing to an attribute value, which won't work. In this case, you should specify the package name directly, like this:

    <style name="my_style"> <item name="com.my.project:tag">some_value</item> </style>

Now Android will be able to resolve where the attribute is defined.