Using attribute to modify a drawable element color

Question

I try to make a custom Drawable by using attribute but I have an inflating error

01-21 11:01:06.171: E/AndroidRuntime(13695): Caused by: android.content.res.Resources$NotFoundException: 
File res/drawable/action_bar_background.xml from drawable resource ID #0x7f020000

My action_bar_background.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" 
 android:shape="rectangle" >
    <gradient
        android:angle="90"
        android:endColor="?attr/ActionBarEndColor"
        android:startColor="?attr/ActionBarStartColor" 
    />
</shape>

My attr.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
     <attr name="ActionBarStartColor" format="reference|color" />
     <attr name="ActionBarEndColor" format="reference|color" />
</resources>

My themes.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="Theme.Theme1" parent="@style/Theme.GreenDroid.Light.NoTitleBar">
        <item name="ActionBarStartColor">@color/greyDark</item>
        <item name="ActionBarEndColor">@color/greyLight</item>
    </style>

    <style name="Theme.Theme2" parent="@style/Theme.GreenDroid.Light.NoTitleBar">
        <item name="ActionBarStartColor">@color/myRed</item>
        <item name="ActionBarEndColor">@color/myWhite</item>
    </style>
</resources>

I don't undestand why, my attribute is a reference or a color, if I "force" the color in themes.xml, it don't work too.

Can anybody help?

I've found this question but it's not resolve my problem.

The only solution i've found, it's to use multiple drawable file with the choosen color and make the reference in the theme file. — Ahmet, Jan 23 '12 at 23:03
This issue was solved in Android L preview, as specified here: https://code.google.com/p/android/issues/detail?id=26251 — Bianca Daniciuc, Jul 10 '14 at 06:50
I found this fixed in Lollipop, but still doesn't work Kitkat and less — Georgy Gobozov, Nov 20 '14 at 21:21

score 13 · Answer 1 · edited May 23 '17 at 11:54

Good news everyone! Starting Lollipop (21) you can use attributes to reference stuff like colors e.g. ?attr/colorPrimary.

Original answer:

As far I know you cannot reference style attributes from drawables, I couldn't find an usage like that in Android platform resources ($ANDROID_HOME/platforms/android-*/data/res/), all I see is that every drawable even for gradient drawables are defined in place or they just reference other drawables like color drawables.

Here is a related bug report for this (star it):

https://code.google.com/p/android/issues/detail?id=26251

You can workaround this by using separate xml drawables like explained at:

https://stackoverflow.com/a/13471695/172670

Unfortunately it will still crash on anything lower than API 21. (So on devices running KitKat or lower it will still crash.) — Lorne Laliberte, Mar 10 '16 at 21:40

Using attribute to modify a drawable element color

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