SimpleBoundService.kt

// MyBoundService.kt
class MyBoundService: Service() {
    // Extend the Binder class and expose the service instance through a method
    inner class MyServiceBinder: Binder() {
        fun getService() = this@MyBoundService
    }

    private val myBinder = MyServiceBinder()
    
    fun doWork() {
        // ...
    }

    override fun onBind(intent: Intent?): IBinder {
        // Support binding to this service
        return myBinder
    }
}

// MyActivity.kt
class MyActivity: AppCompatActivity {
    private val serviceConnection = object: ServiceConnection {
        override fun onServiceConnected(name: ComponentName?, binder: IBinder) {
            val myServiceBinder = binder as MyServiceBinder
            service = myServiceBinder.getService()
        }

        override fun onServiceDisconnected(name: ComponentName?) {
            service = null
        }
    }

    // ...
    private var service: MyBoundService? = null
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.my_activity)
        // ...
        doWorkBt.setOnClickListener {
            service?.doWork()
        }
        // ...
    }
    override fun onStart() {
        super.onStart()
        val intent = Intent(this, MyBoundService::class.java)
        bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE)  
    }

    override fun onPause() {
        super.onPause()
        val intent = Intent(this, MyBoundService::class.java)
        unbindService(intent)
    }
}