This is a gradle task to generate the public.xml file in an Android library project. It assumes all public resources are kept in a res-public/ resource source directory. Providing this as a starting point, but there may be more efficient ways.

generatepublicresources.gradle

import groovy.xml.MarkupBuilder

// Task to generate our public.xml file
// See https://developer.android.com/studio/projects/android-library.html#PrivateResources
// We assume resources within res-public are public
task generatepublicxml {

    def resDir = project.projectDir.absolutePath + "/src/main/res-public"

    // Include the desired res types
    // Note: we don't need the qualified resource directories,
    // since those resources will already be defined in the unqualified directories
    def tree = fileTree(dir: resDir,
            includes: ['**/anim/*.xml',
                       '**/color/*.xml',
                       '**/drawable/*.xml',
                       '**/layout/*.xml',
                       '**/values/*.xml'
            ],
            exclude: '**/public.xml'
    );

    // Create new public.xml with writer
    new File(resDir + "/values/public.xml").withWriter { writer ->
        // Create MarkupBuilder with 4 space indent
        def destXml = new MarkupBuilder(new IndentPrinter(writer, "    ", true));
        def destXmlMkp = destXml.getMkp();

        // GIST NOTE: our project needed the ResourceName suppression, but its not needed in general
        destXml.resources(
                'xmlns:tools': 'http://schemas.android.com/tools',
                'tools:ignore': 'ResourceName'
        ) {
            // Leave file comment
            destXmlMkp.yield "\r\n"
            destXmlMkp.comment("AUTO-GENERATED FILE.  DO NOT MODIFY. public.xml is generated by the generatepublicxml gradle task")

            tree.each { resFile ->

                // use the directory name to get the type
                def type = resFile.getParentFile().getName()

                if (type == "values") {
                    // Resource files under values. Parse the file, and pull out the resource definitions
                    def parsePublicResources = new XmlParser().parse(resFile)
                    parsePublicResources.children().each {
                    
                        // Type is usually the element, but sometimes a type attribute is present
                        // example: <item name="line_spacing_multiplier" format="float" type="dimen">1.4</item>
                        type = it.name()
                        if(it.@type){
                            type = it.@type
                        }

                        // it.@name is value in name= 
                        "public"("name": it.@name, "type": type)
                    }
                } else {
                    // Drawable, layout, etc files
                    "public"("name": resFile.getName().tokenize('.')[0], "type": type)
                }
            }
        }
    }
}