Android Selector Drawable doesnt work with attributes
I encountered the same problem and as of 2019 it hasn't been resolved so you can't have an attribute referenced in a selector as a drawable. I will share the solution I got for the problem as I don't see it posted in here. I found it in the last comment of the bug report also referred by mudit in his answer.
The workaround is basically create a drawable resource that will be the one referring the attribute value.
To illustrate your case the solution would be instead of:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="?attr/colorPrimary" android:state_enabled="true" android:state_window_focused="false"/>
<item android:drawable="?attr/colorPrimaryDark" android:state_pressed="true"/>
<item android:drawable="@android:color/darker_gray" android:state_enabled="false"/>
<item android:drawable="?attr/colorPrimary"/>
</selector>
you would replace the ?attr/* for a drawable resource:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/colorPrimaryDrawable" android:state_enabled="true" android:state_window_focused="false"/>
<item android:drawable="@drawable/colorPrimaryDarkDrawable" android:state_pressed="true"/>
<item android:drawable="@android:color/darker_gray" android:state_enabled="false"/>
<item android:drawable="@drawable/colorPrimaryDrawable"/>
</selector>
The drawables would be defined as:
drawable/colorPrimaryDrawable
<shape xmlns:android="http://schemas.android.com/apk/res/android"android:shape="rectangle">
<solid android:color="?attr/colorPrimary" />
</shape>
drawable/colorPrimaryDarkDrawable
<shape xmlns:android="http://schemas.android.com/apk/res/android"android:shape="rectangle">
<solid android:color="?attr/colorPrimaryDark" />
</shape>
Hope it helps!!
Finally, found the problem. There is a bug in android [pre-lollipop] OS which doesnt allow you to use attr in drawable. Here is the link to bug:
https://code.google.com/p/android/issues/detail?id=26251
Android dev team has released a fix but it works on android L and above.For workaround to this problem, refer to following solution:
How to reference style attributes from a drawable?