MyFirstPlugin.kt

class MyFirstPlugin : Plugin<Project> {

   override fun apply(project: Project) {
       project.android().variants().all { variant ->

           // Make a task for each combination of build type and product flavor
           val myTask = "myFirstTask${variant.name.capitalize()}"

           // Register a simple task as a lambda. We can later move this to its own  
           // class to make our code cleaner and also add some niceties.
           project.tasks.create(myTask){task ->

               // Group all our plugin's tasks together
               task.group = "MyPluginTasks"
               task.doLast {
                   File("${project.projectDir.path}/myFirstGeneratedFile.txt").apply {
                       writeText("Hello Gradle!\nPrinted at: ${SimpleDateFormat("HH:mm:ss").format(Date())}")
                   }
               }
           }
       }
   }
}