Custom attributes in styles.xml

Question

I figured it out! The answer is to NOT specify the namespace in the style.

<?xml version="1.0" encoding="utf-8" ?>
<resources xmlns:android="http://schemas.android.com/apk/res/android">
    <style name="CustomStyle">
        <item name="android:layout_width">wrap_content</item>
        <item name="android:layout_height">wrap_content</item>

        <item name="custom_attr">value</item> <!-- tee hee -->
    </style>
</resources>

above answer is worked for me, I tried a litte change, I declare styleable for a class in resources element.

<declare-styleable name="VerticalView">
    <attr name="textSize" format="dimension" />
    <attr name="textColor" format="color" />
    <attr name="textBold" format="boolean" />
</declare-styleable>

in declare-styleable, the name attribute referenced a class name, so I had a view class call "com.my.package.name.VerticalView", it represented this declare must be use in VerticalView or subclasses of VerticalView. so we can declare style like this :

<resources>
    <style name="verticalViewStyle">
        <item name="android:layout_width">match_parent</item>
        <item name="android:layout_height">36dip</item>

        <item name="textSize">28sp</item>  <!-- not namespace prefix -->
        <item name="textColor">#ff666666</item>
        <item name="textBold">true</item>
    </style>
</resources>

that's why we didn't declare namespace at resources element, it still work.

values/styles.xml

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    ...
    <item name="defaultButtonColor">@color/red</item>
    <item name="defaultButtonHeight">@dimen/dp_100</item>
</style>

values/attrs.xml

<resources>
    <attr name="defaultButtonColor" format="reference" />
    <attr name="defaultButtonHeight" format="reference"/>
</resources>

values/colors.xml

<resources>
    <color name="red">#f00</color>
</resources>

values/dimens.xml

<resources>
    <dimen name="dp_100">100dp</dimen>
</resources>

Using

<Button
    android:layout_width="wrap_content"
    android:layout_height="?attr/defaultButtonHeight"
    android:text="Button"
    android:textColor="?attr/defaultButtonColor"
    />

DEMO

Styler and vince's modification worked for me. I wanted to point out that @vince's explanation may not be entirely accurate.

To test the hypothesis that the name attribute of the declare-styleable matching the name of the custom view class is allowing us to access the custom attribute without a namespace I changed the name of the declare-styleable (the custom view was named TestViewFont:

<declare-styleable name="TextViewFont2">
    <attr name="font" format="integer"/>
</declare-styleable>

I then changed the obtainStyledAttributes call in the custom view to reflect this:

TypedArray ta = context.getTheme().obtainStyledAttributes(attrs, R.styleable.TextViewFont2, 0, 0);

The code still ran. So I don't think it is some kind of introspection by the declare-styleable of the class it is named after.

Thus I am led to believe that any custom attributes can be used to declare a style without referring to a namespace.

Regardless, thanks for all the help guys, it resolved my issue.

• Define some attributes

<declare-styleable name="refreshPullRefreshLayout">
        <attr name="refreshColors" format="reference"/>
        <attr name="refreshColor" format="reference"/>
</declare-styleable>

• Use it in layout file like

<com.aolphn.PullRefreshLayout
     app:refreshColor="@color/main_green"
     app:refreshColors="@array/refresh_color"/>

• Finally use it in style file

  The difference between style file and layout file is we do not add prefiex app:

<style name="refreshStyle">
    <item name="refreshColor">@color/main_green</item>
    <item name="refreshColors">@array/refresh_color</item>
</style>

Try it ,have a nice day,this works for me.

In case it helps anybody else, my mistake was that my custom view class was calling AttributeSet.getAttributeValue e.g.

String fontName = attrs.getAttributeValue("http://schemas.android.com/apk/res-auto", "customFont");

...which was resulting in my custom attribute not being read in for my custom view.

The fix was to use obtainStyledAttributes in my custom view:

 TypedArray styleAttrs = context.obtainStyledAttributes(attrs, R.styleable.MyTextViewStyleable);
 String fontName = styleAttrs.getString(R.styleable.MyTextViewStyleable_customFont);

A hint that this is working correctly is that you can Ctrl/Apple + click on the R.styleable.MyTextViewStyleable_customFont to get taken straight to your attrs.xml definition.

It took me a while to spot this critical difference between my code and the other examples, as the custom attribute worked fine when passed in directly through the layout XML (instead of through a style).