如何在android中添加一个主题属性到android：startColor in gradient drawable？

Question

According to android documentation, android:startColor can take attributes as a value:

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

I am trying to add an attribute to my gradiant drawable, however I get an error. Here is the code for the drawable:

Here is the code in style.xml:

<style name="test" parent="android:Theme">
    <item name="android:startColor">#0b2749</item> 
    <item name="startColor">#0b2749</item>
</style>

When I try to run the activity I get this error message:

01-10 20:47:30.810: E/AndroidRuntime(7279): Caused by: java.lang.UnsupportedOperationException: Can't convert to color: type=0x2

I tried changing ?startColor to ?attr/startColor and still got the same error. I also applied the theme to the activity in the AndroidManifest.xml file.

How can I add a theme attribute to the gradient drawable?

Answer 1

I was having the same problem in one of my drawable in which I want different colors based on the chosen theme. I found a workaround, that doesn't exactly solve the problem, but works for me. Instead of defining the color in my styles, I define the whole drawable as a reference.

In attrs.xml :

<resources>
    <attr name="myDrawable" format="reference"/>
<resources>

And in my style.xml :

<style name="style1">
    <item name="myDrawable">@drawable/myDrawable1</item>
<style>
<style name="style2">
    <item name="myDrawable">@drawable/myDrawable2</item>
<style>

Of course, you need to define two drawables in your drawable folder, myDrawable1 and myDrawable2 , each one having the correct color hard-coded.

And it works fine.

Answer 2

<style name="customTheme" parent="android:Theme">  
    <item name="android:windowTitleBackgroundStyle">@style/WindowTitleBackground</item>
</style>

Add the above code in colors.xml in values folder and the following code in styles.xml

<color name="titlebackgroundcolor">#FFFFFF</color>
<color name="titletextcolor">#000000</color>

Answer 3

Looks like you just made a small mistake for your color. Android takes the #[alpha] [hex] type of input for colors. You just provided the hex part. Android doesn't support this, hence the UnsupportedOperationException .

Try using this:

<item name="android:startColor">#FF0b2749</item>

I can't guarantee that this works though, as I have never worked with gradients in combination with a style.