How to create the custom attributes to reference color from style.xml in android

In this blog,

We have shown you how to make a custom attribute and how to reference color attribute in drawable.

You can define attributes in the top <resources> element or inside of an <declare-styleable>element.

Note: All attributes share the same global namespace. That means that even if you create a new attribute inside of an <declare-styleable> element it can be used outside of it and you cannot create another attribute with the same name of a different type.

An <attr> element has two XML attributes name and format. name lets you call it something and this is how you end up referring to it in code, e.g.,R.attr.my_c_attribute The format attribute can have different values depending on the ‘type‘ of the attribute you want.

• reference – if it references another resource id (e.g, “@color/my_color”, “@layout/my_layout”)
• color
• boolean
• dimension
• float
• integer
• string
• fraction
• enum – normally implicitly defined
• flag – normally implicitly defined

There are few simple steps,

1. Define the colors for the specific theme in your colors file:
   
   <?xml version="1.0" encoding="utf-8"?> <resources> <color name="my_link_color1">#0077CC</color> <color name="my_link_color2">#626262</color> </resources>

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   <?xml version="1.0" encoding="utf-8"?> <resources>     <color name="my_link_color1">#0077CC</color>     <color name="my_link_color2">#626262</color> </resources>

2. Create file res/values/attrs.xml with contents:
   
   <?xml version="1.0" encoding="utf-8"?> <resources> <attr name="myLinkColor" format="reference" /> </resources>

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   <?xml version="1.0" encoding="utf-8"?> <resources>     <attr name="myLinkColor" format="reference" /> </resources>

3. Suppose we have 2 themes in our styles.xml (Theme1 and Theme2) define:
   
   <style name="Theme1" parent="Theme.AppCompat.Light.DarkActionBar"> <item name="myLinkColor">@color/my_link_color1</item> </style> <style name="Theme2" parent="Theme.AppCompat.Light.DarkActionBar"> <item name="myLinkColor">@color/my_link_color2</item> </style>

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   <style name="Theme1" parent="Theme.AppCompat.Light.DarkActionBar">     <item name="myLinkColor">@color/my_link_color1</item> </style>   <style name="Theme2" parent="Theme.AppCompat.Light.DarkActionBar">     <item name="myLinkColor">@color/my_link_color2</item> </style>

4. Use the color in the XML:
   
   android:textColor="?attr/myLinkColor"

   1	android:textColor="?attr/myLinkColor"

   
    

Maybe this blog is helpable for you.

Source: https://github.com/android/