kotlin broadcast receiver example

 kotlin broadcast receiver example

In addition to providing a mechanism for launching application activities, intents are also used as a way to broadcast system-wide messages to other components of the system. This involves the implementation of Broadcast Intents and Broadcast Receivers, both of which are the topic of this chapter.

Broadcast intents are Intent objects that are broadcast via a call to the send broadcast(), send a sticky broadcast() , or sendOrderedBroadcast() methods of the Activity class (the latter being used when results are required from the broadcast). In addition to providing a messaging and event system between application components, broadcast intents are also used by the Android system to notify interested applications about key system events (such as the external power supply or headphones being connected or disconnected).

1.MainActivity.kt:

import android.content.Intent

import android.content.IntentFilter

import android.os.Bundle

import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

// register the receiver in the main activity in order

// to receive updates of broadcasts events if they occur

lateinit var receiver: AirplaneModeChangeReceiver

override fun onCreate(savedInstanceState: Bundle?) {

super.onCreate(savedInstanceState)

setContentView(R.layout.activity_main)

receiver = AirplaneModeChangeReceiver()

// Intent Filter is useful to determine which apps wants to receive

// which intents,since here we want to respond to change of

// airplane mode

IntentFilter(Intent.ACTION_AIRPLANE_MODE_CHANGED).also {

// registering the receiver

// it parameter which is passed in registerReceiver() function

// is the intent filter that we have just created

registerReceiver(receiver, it)

}

}

// since AirplaneModeChangeReceiver class holds a instance of Context

// and that context is actually the activity context in which

// the receiver has been created

override fun onStop() {

super.onStop()

unregisterReceiver(receiver)

}

}

2.activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout

xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

tools:context=".MainActivity">

</androidx.constraintlayout.widget.ConstraintLayout>

3.AirplaneModeChangeReceiver.kt:

import android.content.BroadcastReceiver

import android.content.Context

import android.content.Intent

import android.widget.Toast

// AirplaneModeChangeReceiver class extending BroadcastReceiver class

class AirplaneModeChangeReceiver : BroadcastReceiver() {

// this function will be executed when the user changes his

// airplane mode

override fun onReceive(context: Context?, intent: Intent?) {

// intent contains the information about the broadcast

// in our case broadcast is change of airplane mode

// if getBooleanExtra contains null value,it will directly return back

val isAirplaneModeEnabled = intent?.getBooleanExtra("state", false) ?: return

// checking whether airplane mode is enabled or not

if (isAirplaneModeEnabled) {

// showing the toast message if airplane mode is enabled

Toast.makeText(context, "Airplane Mode Enabled", Toast.LENGTH_LONG).show()

} else {

// showing the toast message if airplane mode is disabled

Toast.makeText(context, "Airplane Mode Disabled", Toast.LENGTH_LONG).show()

}

}

}