Create a custom Drawable and use it in XML

Question

I am busy creating a less complicated version of NinePatchDrawable that tiles the inner panels instead of stretching them.

I can implement the actual logic to do the rendering and such.

However, I can't find documentation about how to use this Drawable in the XML files. Is this possible? That is, can I have a <tileable-nine-patch> , or some such, tag I can use to define resources?

Answer 1

Unfortunately it is not possible to use custom drawables in XML files (for API 23 and below) due to potential security issues. See here for a Google Groups thread about this very topic with a response from Romain Guy, one of the Android developers.

You can still use them in your Java code though.

Update:

As LeoFarage points out in the comments, starting in API 24 you can now use custom drawables in XML files but only within your application package.

Answer 2

Starting Android API 24, custom Drawables classes can be used in XML only within your package.

Custom drawables classes may be used in XML in multiple ways:

Using the fully-qualified class name as the XML element name. For this method, the custom drawable class must be a public top-level class.

<com.yourapp.MyCustomDrawable
     xmlns:android="http://schemas.android.com/apk/res/android" 
     android:color="#ffff0000"/>

Using drawable as the XML element name and specifying the fully-qualified class name from the class attribute. This method may be used for both public top-level classes and public static inner classes.

<drawable xmlns:android="http://schemas.android.com/apk/res/android"
 class="com.myapp.MyTopLevelClass$InnerCustomDrawable"
 android:color="#ffff0000" />

Note: that is not supported by support library.

Answer 3

Too late, but since there is no clear answer here what I tried. As @Casabancais answer copied from Android docs.

Create a drawable xml named say custom_drawable.xml with this

<?xml version="1.0" encoding="utf-8"?>
<drawable xmlns:android="http://schemas.android.com/apk/res/android"
    class="com.my.package.path.MyCustomDrawable"
    android:color="#ffff0000" />

com.mypackage.MyCustomDrawable.java should be your java drawable class

Then you can use it in lets say background tag for any xml like this

<androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:background="@drawable/custom_drawable"
        android:layout_height="wrap_content">