使用属性修改可绘制元素颜色

我尝试使用属性制作自定义Drawable，但出现膨胀错误

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

我的 action_bar_background.xml

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>

我的 attr.xml

My attr.xml

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

我的主题.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>

我不明白为什么，我的属性是引用或颜色，如果我在 themes.xml 中强制"颜色，它也不起作用.

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.

有人可以帮忙吗?

我发现了这个问题 但它不能解决我的问题.

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