Inject XML resources after variants are merged

resourceinjection.gradle

// Here's a trick to get XML injected into the APK.
// Be careful not to merge-conflict with existing parameters, as this occurs after the mergeResources step, and the behavior is likely undefined.
// was added to app/build.gradle after applying android plugin.

android.applicationVariants.all { variant ->
       // Supports both 0.12.+ and 1.+ of Android gradle plugin by getting all processResourceTasks:
       def tasks = []
       // Multidex has multiple process resource tasks
       if (variant.hasProperty('outputs')) {
           for (output in variant.outputs) {
               tasks.add(output.processResources)
           }
       } else {
           tasks.add(variant.processResources)
       }
   // FIXME: You would not want to use doFirst.
   // Instead, you'd want to add a single task and put it immediately before each of these tasks, (using .dependsOn to inject the task.)
   // ALSOFIXME: I'm copying more than once if you're using multidex because I'm doing this for each task which isn't ideal.
   // If you just used a fresh task, and .dependsOn, you wouldn't run into this.
   tasks.each { it.doFirst({
           copy {
               // This folder would be project/app/xml, and contain the xml files you want
               from 'xml/'
               // NOTE: hardcoded path, you'd want to replace debug with ${task.dirName}, I believe.
               into 'build/intermediates/res/debug/values'
               include '**/*.xml'
           }
       })
   }
}