MainActivity_SmsSender.kt

class MainActivity : AppCompatActivity() {
 
  companion object {
        const val RC_CODE = 101
        const val TAG = "debug_MainActivity"
        const val SENT = "SMS_SENT"
        const val DELIVERED = "SMS_DELIVERED"
  }
  
  // Views
  @BindView(R.id.toolbar) lateinit var toolbar: Toolbar
  @BindView(R.id.btnSendSMS) lateinit var sendSMS: FloatingActionButton
  @BindView(R.id.fieldNumber) lateinit var fieldNumber: TextInputEditText
  @BindView(R.id.fieldMessage) lateinit var fieldMessage: TextInputEditText
  
  private lateinit var sentPI: PendingIntent
  private lateinit var deliveredPI: PendingIntent
  
  override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        ButterKnife.bind(this)

        // Receiver listener for SMS
        sentPI = PendingIntent.getBroadcast(this, 0, Intent(SENT), 0)
        deliveredPI = PendingIntent.getBroadcast(this, 0, Intent(DELIVERED), 0)
        // --when the sms has been sent
        this.registerReceiver(object : BroadcastReceiver() {
            override fun onReceive(context: Context?, intent: Intent?) {
                when (resultCode) {
                    Activity.RESULT_OK ->
                        Toasty.success(this@MainActivity, "SMS sent success!", Toasty.LENGTH_SHORT, true).show()
                    SmsManager.RESULT_ERROR_NO_SERVICE ->
                        Toasty.error(this@MainActivity, "No active network to send SMS.", Toasty.LENGTH_SHORT, true).show()
                    SmsManager.RESULT_ERROR_RADIO_OFF ->
                        Toasty.error(this@MainActivity, "SMS not sent!", Toasty.LENGTH_SHORT, true).show()
                }
            }
        }, IntentFilter(SENT))

        // --When SMS has been delivered
        this.registerReceiver(object : BroadcastReceiver() {
            override fun onReceive(context: Context?, intent: Intent?) {
                when (resultCode) {
                    Activity.RESULT_OK ->
                        Toasty.success(this@MainActivity, "SMS delivered.", Toasty.LENGTH_SHORT, true).show()
                    Activity.RESULT_CANCELED ->
                        Toasty.error(this@MainActivity, "SMS not delivered.", Toasty.LENGTH_SHORT, true).show()
                }
            }
        }, IntentFilter(DELIVERED))

        initToolbar()
        initComponent()

    }
  
  private fun initToolbar() {
        setSupportActionBar(toolbar)
        supportActionBar?.title = resources.getString(R.string.app_name)
  }
  
  private fun initComponent() {
        // Action send SMS
        sendSMS.setOnClickListener {
            if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.SEND_SMS) == PackageManager.PERMISSION_GRANTED) {

                val message = fieldMessage.text.toString()
                val number = fieldNumber.text.toString()
                if (message.isEmpty() || number.isEmpty())
                    Toasty.error(this@MainActivity, "Please enter number and message!", Toasty.LENGTH_SHORT, true).show()
                else {
                    try {
                        val smsManager = SmsManager.getDefault()
                        smsManager.sendTextMessage(number, null, message, sentPI, deliveredPI)
                    } catch (e: Exception) {
                        Log.d(TAG, e.message)
                        e.printStackTrace()
                        Toasty.error(this@MainActivity, "SMS Failed to send, please try again!", Toasty.LENGTH_SHORT, true).show()
                    }
                }

            } else
                ActivityCompat.requestPermissions(this, arrayOf(android.Manifest.permission.SEND_SMS), RC_CODE)
        }     
  }