CODEWITHSUNDEEP
androidandroid-styles
jnovacho
jnovacho

Reputation: 2903

How to use Android styles inheritance with different qualifiers

I'm working on Android app and I have to support API 19 and higher. So my styles structure looks like this:

res
   values
          styles.xml
   values-v21
          styles.xml

In styles.xml I have

<style name="customButton" parent="Base.Widget.AppCompat.Button">
    <item name="android:focusable">false</item>
    <item name="android:clickable">true</item>
</style>

and in the v21/styles.xml I have 

<style name="customButton" parent="customButton">
    <item name="android:elevation">10dp</item>
</style>

While this works, it doesn't seem right. And the Android studio is complaining about cyclic references. That is because the v21/customButton has technically itself as a parent.

I cannot rename the v21/customButton to customButton21 because then I would have to create two versions of everything that uses this style. While only difference is the new attribute added in API 21.

What is the correct way to solve this issue? Maybe create base-style.xml and then reference it in specific API styles?

PS: This question applies to any qualifiers, not only the API.

Upvotes: 0

Views: 444

Answers (1)

jnovacho
jnovacho

Reputation: 2903

I have settled for following solution:

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <attr name="buttonStyle" format="reference" />
</resources>

values/styles.xml

<resources>
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <item name="@attr/buttonStyle">@style/buttonStyleBase</item>
    </style>

    <style name="buttonStyleBase">
        <item name="android:gravity">left</item>
        <item name="android:textSize">20sp</item>
    </style>
</resources>

values-v21/styles.xml

<resources>
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <item name="@attr/buttonStyle">@style/buttonStyle21</item>
    </style>

    <style name="buttonStyle21" parent="buttonStyleBase">
        <item name="android:elevation">15dp</item>
    </style>
</resources>

And then to use it:

<Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        style="?attr/buttonStyle" />

This way I can inherit the base style which can be as complex as I need and apply only changes that are relevant to another SDK version.

Upvotes: 1

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