Android Selector Drawable doesnt work with attributes

Question

I am using attr to create a selector drawable for my project so that once i change theme colors, i dont have to make any change in the drawable file. I am using following libs:

compile 'com.android.support:appcompat-v7:+'
compile 'com.android.support:cardview-v7:+'
compile 'com.android.support:design:22.2.0'

Here is the source code for drawable:

<?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>

in this same code, if i replace attributes with colors defined in colors.xml file, the same drawable works.

Sample drawable with colors:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@color/color_primary" android:state_enabled="true" android:state_window_focused="false"/>
    <item android:drawable="@color/color_primary_dark" android:state_pressed="true"/>
    <item android:drawable="@android:color/darker_gray" android:state_enabled="false"/>
    <item android:drawable="@color/color_primary"/>
</selector>

Thanks in advance!

Answer 1

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?

Answer 2

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!!