How to create a Thread with an Looper, called by a Handler

thread-looper-handler.kt

// Understanding Handler and Looper in Android
// by Rahul Rastogi
// https://medium.com/@rastogi.tech/understanding-handler-and-looper-in-android-c6fa673c6822

var handler: Handler? = null

Thread {
  Looper.prepare() // Creating a Looper for this thread.

  // Creating a Handler for given Looper object.
  handler = Handler(Looper.myLooper(), // get Looper for current Thread
    Handler.Callback { msg ->
      // Processing incoming messages for this Handler.
      // Receiving extras from Message
      val bundle: Bundle? = msg.data

      Log.d("", "Handler:: Extras: ${bundle}")
      Log.d("", "Handler:: Background Thread ID ${Thread.currentThread().id}")

      // Looper.myLooper().quit()

      return@Callback true
    }
  )

  Looper.loop()
}.start()

Log.d("", "Handler:: UI Thread ID ${Thread.currentThread().id}")

// Posting a runnable to the handler
handler?.post {
  // Thread's ID is of thread.
  Log.d("", "Handler:: Background Thread ID ${Thread.currentThread().id}")
}

// Sending data using Message object. Handler's handleMessage(msg: Message?) method will receive this Message and perform appropriate action.
val extras = Bundle().apply {
 putInt("PRICE", 100)
 putString("PRODUCT_NAME", "Table Lamp")
}
            
val message = Message.obtain(handler).apply {
  data = extras
}
            
handler?.sendMessage(message)